Notes on the Troubleshooting and Repair of Optical Disc Players and Optical Data Storage Drives


LaserDisc, MiniDisc, DVD, WORM, CD-R, MO
Version 1.57 (12-Jul-23)

Copyright © 1994-2022
Samuel M. Goldwasser
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Sci.Electronics.Repair FAQ Email Links Page.

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Table of Contents

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    Author and Copyright

    Author: Samuel M. Goldwasser

    For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page.

    Copyright ©; 1997-2021
    All Rights Reserved

    Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

    1. This notice is included in its entirety at the beginning.
    2. There is no charge except to cover the costs of copying.


    Working on optical storage equipment entails a number of personal risks: electrical, laser, mechanical, as well as the possibility of irreversible damage to the equipment and loss or corruption of data due to improper repair or adjustment.

    We will not be responsible for damage to equipment, your ego, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury or worse that may result from the use of this material.

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    Scope of this document

    While compact disc (CD) players and CDROM drives account for the vast majority of optical disc platforms in the known universe, there are other types in use for both entertainment and data storage applications. These include:

    These all use optical technology very similar to that of the compact disc and CDROM. Thus, most problems with these cousins of the CD will be similar. See the document: "Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives" for an introduction to the basic technology, general maintenance procedures, and diagnosis of most common problems. This document addresses those aspects of the technology and repair that are unique to each of these other formats. Problems with Sony PlayStation PSX (and similar) CDROM-like game machines are covered there as well.

    Once CD (and DVD) rewritable technology becomes more popular (and lower in price), these will be added. I currenty have little information on this equipment.

    Contributions are always welcome as you will note that there really isn't that much specific information at the present time on anything other than LaserDisk players and even this is sparse. I don't expect that much interest in or offers of CD-R, WORM, or MO repair information. However, MiniDisc has some sort of a following and we are destined to be inundated with DVD problems in the near future as they replace CDs as the equipment of choice. I am still waiting to see the inside of a DVD player - working or otherwise :-).


    In addition to the usual safety precautions outlined in the document: "Safety Guidelines for High Voltage and/or Line Powered Equipment", some of this equipment has the added risk of vision damage from the higher power lasers that may be used for disk writers or recorders.

    This isn't that much of a problem with LaserDisk players since the laser power is likely (but not guaranteed!) to be similar to that of a CD player where relatively minimal precautions are adequate.

    However, for the technologies which can record or write on an optical disk, the laser power may be much higher and instant irreversible damage to vision is quite possible. Furthermore, these are almost always IR (infra-red) lasers which are for all intents and purposes, invisible. Proper precautions are essential and laser-blocking goggles are definitely recommended whenever the unit is powered without a laser shield in place. Once you damage both of your original equipment eyesballs, you don't receive any replacements (even if they are still under warranty - read the fine print of your contract)!

    General safety precautions:

    While there are fewer potential dangers involved in servicing an LD player or MO drive compared to a TV, monitor, or microwave oven, precautions are still required when working with the cover removed. These relate to electrical connections to the AC line, getting caught in the mechanisms, and exposure to the laser beam:

    For more information on CD and optical disc technology

    Philips/Magnavox used to have a very nice on-line introduction to a variety of consumer electronics technologies. Although their site has disappeared - and even people who work for them have no clue - I have now recovered several of the articles including those on TVs, VCRs, camcorders, satellite reception, and connections. See the Introductory Consumer Electronics Technology Series. These as well as most or all of the other articles, as well a glossary and much more, can be also be accessed via the Internet Archive Wayback Machine. Copy and paste the following URL into the search box:

    The earliest (Nov 09, 1996) archive seems to be the most complete.

    Also check out:

    The following site has a variety of information on CD and DVD technology:

    A site with CD-R specific information including some repair tips is:

    An extensive amount of information on other optical disc/k technologies with many useful links can be found at:

  • Back to Optical Drive Repair FAQ Table of Contents.

    Technology Specific Principles of Operation

    LaserDisc (LD) Players

    This is actually the oldest of the optical disc technologies to be introduced to the consumer market and most of its applications are for analog video storage - feature length movies and interactive learning tools and arcade video games.

    In terms of performance, video quality from the LaserDisc medium can be far superior to even SVHS and SuperBeta, and competitive with DVD when viewed on a correspondingly high quality TV or monitor. Like a CD and unlike tape, access to any scene or even frame is quite fast. This is definitely a significant advantage for the casual viewer but was the enabling technology for interactive instruction and games. With up to 54,000 or more individually accessible frames on a side, this was a potentially very powerful way to present information as combinations of stills and moving segments and permit context dependent control of access or video action.

    However, note that except for some control codes representing a very small number of bits that identify things like format and time/chapter/frame on the disc, LaserDisc is a totally analog format as far as the electronics are concerned (though the information on the disc surface is in pits and lands as with CDs and DVDs). The video and audio channels are assigned separate frequency bands and are demodulated with analog circuitry. There is no digital error checking, though some players include a 1 line video memory to help conceal dropouts by replacing missing video with the line above. And, some newer LD players may have a digital frame store to allow for noise-free implementation of functions like freeze frame, slow motion, and so forth, on CLV discs (see below).

    There are two basic LD formats: Constant Angular Velocity (CAV) and Constant Linear Velocity (CLV). For CAV, the disc rotates at a constant 1,800 rpm (NTSC) or 1,500 rpm (PAL). All special effects like still/freeze frame and single frame forward or reverse, slow motion, and individual frame addressing are available in CAV mode. Some players can search to a specific frame number in only a few seconds. However, the maximum length of program material for CAV is only about 1/2 hour per side as there is less efficient use of space as the pickup moves toward the outside of the disc. For CLV, the total program time approximately doubles to 1 hour per side. The rotation rate of the disc slows down (like a CD or DVD) as the pickup moves toward the outer edge. However, without a sophisticated digital frame store, most special effects are disabled (or don't work at all well). Fast scan is functional but except near the beginning of the disc where the rotation rate is similar to that of CAV and the video on successive tracks likes up, the result is a broken up picture with loss of color. There may be no sound with special effects for either mode.

    Most feature length movies were released in CLV to achieve the maximum time on a each disc. However, if there was enough space without increasing the number of discs or sides, some potions might be in CAV to have the special effects.

    There were a variety of audio formats used, the most common being stereo with quality approaching that of CDs.

    The video aspect ratio was something that seemed to be played with quite a bit with later releases tending toward various letter-box and wide-screen formats. Most will play fine on any standard TV or monitor that supports the "normal" 4:3 aspect ratio, but the top and bottom will be black. And when this gets to be extreme like 2.35:1, there is a loss of quality simply because so much of the screen (and resolution) is being wasted. However, there were also a relatively small number of "Squeeze" format LDs. These expected a true 16:9 aspect ratio TV and will look squashed horizontally on a normal 4:3 aspect ratio set unless it has a corresponding mode.

    High-end video enthusiasts used to swear by LaserDisc technology but this medium never caught on due to the relatively high cost of both the equipment and the software (movies), limited rental availability, and because it is a play-only media. In addition, the capacity (NTSC) of a single LaserDisc is around 1 hour total (both sides) for CAV or 2 hours (both sides) for CLV requiring more frequent disc changes than for VHS/Beta or now DVD even if the player had dual laser pickups or a mechanism for moving a single pickup to read both sides.

    Nowadays, LaserDisc is considered history, replaced by the DVD which is smaller, cheaper, with additional features and flexibility, and with potentially superior picture quality. However, there is still an active market in used LaserDiscs and players, and for many purposes, the LaserDisc - especially given the declining cost since so many are dumping it - is an attractive alternative to putting together a high quality video collection inexpensively. Prices on eBay for individual LaserDiscs currently range for under $1 to perhaps $30 (depending on the title and condition). The winning bid price for perfectly usable - and sometimes full featured - players may be less than the shipping cost. At any given time, there are typically over 100 LD players for sale on eBay ranging from working vintage machines from the early '80s or before, to the state-of-the-art when production was discontinued.

    The LD disc is a sandwich of two 1.2 mm thick 12" platters glued together with the information layers on the inside. In fact, the thickness, track spacing, and pit and land sizes, are very similar to that of CDs and probably provided the basis for the ultimate CD specification. But there were never any double-sided CDs. Most DVDs are a sandwich of a 0.6 mm thick platter with the information content, and a 0.6 mm blank blank platter to make the DVD 1.2 mm thick. The DVD specification also supports two sided DVDs, which are a sandwich like LDs but only 1.2 mm thick, as well as two layer DVDs have information recorded at two depths but are read from the same side. But there were never any two sided CDs.

    The basic eletro-optical mechanism is similar to that with a CD, DVD, HD DVD, or Blu-ray disc/k including the techniques used for beam generation, focusing, and tracking. However:

    For general information on LaserDisc, see: Bob Niland's LaserDisc FAQs. These include the format, features, problems, and more.

    Note that the LaserDisc format is totally and absolutely different than that of the RCA Selectavision CED (Capacitance Electronic Disc). Even though the discs are the same size, they are totally incompatible and will likely cause damage to both the disc and player if any attempt is made to even load one type into the other type of machine. This last gasp of the USA consumer electronics industry reportedly costing RCA several hundred million dollars to develop was based on such archaic technology as to be laughable, at least in hind-sight when lasers were still expensive and optical disc technology was in its infancy. CED used a stylus like old fashioned records. The stylus was a capacitance sensor that mechanically tracked a physical groove (almost 10,000 per inch) in a pressed vinyl disc rotating at 450 rpm (compared to 33-1/3 rpm for the most common long playing record). Wear, damage, dust, dirt, and other contamination was a major concern so the disc was enclosed in a caddy and cleaning was not really possible. It's a minor miracle these worked at all! However, there are still collectors out there who keep the spirit of the format alive.

    For more information than you could possibly ever want, see Capacitance Electronic Discs.

    (From: Mark Zenier (

    The original version is covered in The "Television Engineering Handbook" edited by Benson from McGraw-Hill, 1986. Don't know about the newer version with digital sound. (Or what the newer edition of the book covers, either).

    It's an analog FM system at 8 MHz that records the composite signal, with two FM audio carriers at 2.3 and 2.8 MHz.

    So what about the RCA "CED" video player?

    CED stood for something like "Capacitive Electronic Disc" probably with a "Selectavision" label.

    It is NOT related to LaserDisc technology and does not use an optical pickup.

    If you found one of these, you have a classic dinosaur! The CED system was something RCA spent $200-300 million to develop about the same time that LaserDisc technology was being perfected. Guess which won!

    And, this was shortly after the same company spent a similar vast amount of money on another consumer electronics dud. It was also named Selectavision if I recall correctly and used optical scanning of 4 mm (??) movie film.

    CED uses a capacitive contact sensor 'sled' running in a grooved disc.

    The pickup actually rides on the disc like the stylus on a phonograph record. The sensor detects minute changes in the capacitance between the tip of the pickup and the metallized surface of the disc embossed with millions of tiny bumps and valleys.

    This really isn't that bad - the system DID work but suffered from some of the same problems as records - wear, critical tracking requirements, etc.

    If you are trying to resurrect a CED player, you better have the discs you want because they will not be available at your neighborhood video store!

    Since it is more than 15 years old, there can be any number of problems with the equipment just from age and non-use. These are likely to be both mechanical (gummed up grease, dirt), and electronic (dried up electrolytic capacitors in the power supply, bad connections, etc.).

    However, chances are good that it wasn't actually broken to begin with since consumers likely gave up on this technology before it actually failed - there just wasn't enough movies/programming available.

    Start by checking the obvious, reseating all connectors, testing power supply voltages and for ripple, etc.

    It certainly would be cool to get working.

    MiniDisc (MD) recorders/players

    The MiniDisc cartridge looks somewhat like a small (2-1/2") version of a 3-1/2" computer diskette. Both players (around) $400 and player/recorders (around $700) have been introduced with disappointing sales. Not enough prerecorded material was available and the prices were too high to lure people away from the convenience, low cost, and limitless variety of the audio cassette medium.

    MDs may be pressed like CDs with the information encoded in pits and lands. This is the way prerecorded play-only MiniDiscs are made.

    For recording, the MiniDisc technology uses a higher power laser beam (upped to 5 mW at the disc surface) to heat a magneto-optically active coating to above its cure point (where magnetization is lost). A writing coil in close proximity to the back of the Minidisc is used to switch the magnetic field polarity (N or S) of the coating as it cools. Thus, the laser beam may be thought of as 'softening up' the magnetic material but the actual writing is by the coil. This is not the same way most other writable magneto optical drives are implemented. See the sections: "WORM drives" and "Magneto optical drives" for more details on these other media.

    For playback of this magneto-optical (MO) recording, the pickup uses what is known as the 'magneto-optic Kerr effect'. When a polarized laser beam is reflected from the disc coating, its polarization orientation is rotated slightly depending on the magnetic field polarity (N or S). This rotation is small (about 1%) but enough to permit detection. However, since it is so small, it isn't surprising that there can be problems with the optics and front-end electronics for MO readback.

    Thus, the MiniDisc pickup and front-end operates in three modes: spatial (pits and lands) read, MO read, and MO write.

    The basic mechanism and optical pickup is similar to that of a CD including the techniques used for beam generation, focusing, and tracking. However:

    Digital Versatile (or Video) Disc (DVD)

    The DVD is destined to replace the CD as *the* optical medium of choice in the near future. This will happen if for no other reason than manufacturers will stop producing CD players (since DVD players will be able to read CDs).

    The basic components are very similar and thus cost of manufacture will be similar. So, why produce old fashioned equipment?

    The DVD permits storage of up to 4.5 GB per information layer with up to 2 of these on each side (one under the other) for a total of 18 GB if fully implemented. This means (per layer):

    The 8-fold increase in storage capacity per layer is accomplished through a number of incremental enhancements to the basic CD technology including: This permits: For readout on both sides of a dual-sided DVD, dual optical pickups can be used where the user is willing to pay for this significant added expense!

    From a marketing perspective, it is essential for DVD equipment to support the CD format. However, since DVDs and CDs differ in terms of feature size, track spacing, thickness, and so forth, it would not be very effective to simply shine the DVD pickup at a CD! Either of two approaches may be taken:

    Are blue lasers used in DVDs?

    The readout laser for DVDs is red, around 650 nm. This is similar in color to a typical red LED.

    Some people seem to think blue lasers are used for DVDs. One reason may be that manufacturers are putting blue illumination on the front panels and maybe even inside the disc compartment of DVD players - solely for marketing reasons.

    However, blue or UV lasers (e.g., argon or krypton ion) may be used to write the glass master for DVD (as well as CDs) where the shorter wavelength results in crisper more accurate rendition of the pits and lands of the information layer. Of course, these machines cost $250,000.

    Converting to a shorter wavelength laser for readout won't help anything except the manufacturer's bottom line assuming they could charge much more for the hype than the additional cost of the laser. Currently, the only viable option is the Nichia 400 nm violet laser diode which go for about $2K each! To take advantage of a shorter wavelength laser, the entire standard would need to be revamped. I have already named the new standard: the "Digital Ultra Disc" or DUD. :) Once those violet lasers (or alternatives) come down in price, there is little doubt that the World will be treated to yet another advance in technology whether anyone wants it or not.

    Will DVD be the killer format?

    There has been and will continue to be a lot of hype with respect to the incredible advantages of the Digital Video (Versatile) Disc for everything from computer multimedia to HDTV.

    Here is my take. My track record isn't great on predicting the future as my crystal ball has been broken for a long time, so don't buy or sell shares in any company based on these comments!

    DVD will do very well for data storage since due to its much higher capacity compared to CDROMs (5 to 20 GB versus .64 GB), it will serve an important purpose in the increasingly interactive applications and games to come.

    Full size DVD will be overkill for many audio applications. At the normal CD audio sampling rate of 44.1 K/second, the smaller DVD format will hold over 8 hours of music. Whether people will be willing to pay the expected price for a DVD with several hours of music is questionable. There certainly will be many good reasons to do this - full concerts or operas on a single disc, for example. I would expect the average total length of normal musical DVDs to increase beyond what is typical of CDs as well.

    However, mini-DVDs are possible. A 3-1/2" format would hold about 1/3 as much as a full size DVD or over 2 hours of music. This or an even smaller format would be ideal for discman applications.

    What about multilinqual sound tracks? Sure, this capability may save money by requiring pressing of only one disc to support multiple markets. But, few people will have a need to pay for this.

    There are no doubt all sorts of applications that have not been identified yet for which the DVD is ideal. However, the hopes of the industry are pegged to DVD's success for video - in part, to replace the consumer (VHS) VCR. Unfortunately, It is here where I believe DVD has its greatest weaknesses.

    Many of the specifications have been developed tailored to today's video standards, not HDTV. The DVD is supposed to be superior to both VHS VCR and laserdisc formats. However, this is in comparison to standards (NTSC and PAL) that are close to celebrating their 50th birthday. Even the quality advantages are questionable as so much depends on the MPEG-2 encoding used to compress the vast amount of video information onto the DVD.

    Video tape and laserdiscs do not care what is recorded on them - they are equally good or equally poor for static scenes as well as explosive action shots. This is not true of DVDs. Complex images and rapid scene chances require more bits to minimize artifacts. And, the types of artifacts that are introduced are not those one expects from poor reception or bad tapes. It will take a great deal of effort on the part of the companies who will be converting original movies and other source material to the DVD to do justice to the format. It may simply be impossible for certain action sequences. The result may be 'pixelation' or momentary blockiness, erratic motion, momentary freezes, and so forth - not just slight fuzziness or snow. It is not known how the general viewer will accept these. Developers of source material will not be free to put in whatever they desire. The medium may break down when presented with too much fast complex action or rapid scene changes.

    The situation gets even murkier for HDTV where the required amounts of data and data transfer rates increase dramatically. Depending on HDTV format, this could be anywhere from 2:1 or 8:1 - or more. If the DVD is marginal now, what does this say for HDTV?

    Initially, DVD will not have record capability. Thus, there will be no compelling reason to switch over and throw out your VCR especially if the quality isn't dramatically better. The majority of consumers don't care that much about picture quality anyhow. Beta, S-VHS, and laserdisc, all have substantially better picture quality than normal VHS and NTSC broadcasts. It has not mattered due to various usability issues and marketing stupidity. The critical mass was never reached with respect to availability of source or rental tapes or discs. Thus, these have been relegated to niche markets and niche markets don't drive the industry.

    Will DVDs turn into yet another Edsel, Selectavision, or Betamax? Only time will tell but the industry must make a deliberate effort to assure the quality of the initial releases or else DVD's future as a video media will be sealed before it gets off the ground even if the technology there.

    DVD FAQ?

    Well one, at least:

    WORM drives

    A large number of technologies have been introduced to provide storage of large amounts of information on optical platters with varying degrees of flexibility.

    The earliest were called WORM (Write Once Read Many) drives. Writing resulted in an irreversible change in an information layer. Thus, data could be written but not erased and rewritten (though just erasing a block might be possible). Heating with the writing laser beam resulted in damage (ablating) of a coating. Reading is similar to that used for CDs and other optical technologies.

    Typical capacity was 650 MB per side. Disks could be one sided or two sided.

    This is somewhat similar to the technology used in CD-R drives though many variations have been developed which vary mostly in the details.

    Unlike CDs, MDs, and LDs, these optical discs are formatted more like hard drives or diskettes with circular (not spiral) tracks and fixed sectors - some of which are visible to the naked eye since they are physically etched on the disk itself.

    The laser power for WORM drives is typically higher than for read-only drives when in writing mode - likely in the 10s of mW range. 30 mW is one number I have heard. Modern drives all use IR emitting laser diodes.

    The basic mechanism and optical pickup is similar to that of a CD including the techniques used for beam generation, focusing, and tracking. However:

    Magneto-optical drives

    Most modern optical drives use magneto-optical techniques in some ways similar to the MiniDisc. However, unlike the MD, the laser beam is switched at high speed to alter the magnetic properties of the coating and a write cycle is usually a two step process:
    1. Energize the bias coil with the '0' polarity (e.g., N).

    2. Erase a block by turning on the laser as that area of the disk passes under the pickup.

    3. Reverse the polarity of the bias field to that of a '1' (e.g., S).

    4. On the next revolution, write the information by selectively heating only those regions destined to become '1's in the stored pattern.
    The laser power for MO drives is typically higher than for read-only drives and likely in the 10s of mW range. Modern drives all use IR emitting laser diodes.

    The media is usually enclosed in a cartridge for protection with a door that opens automatically when inserted into the drive. Capacity is typically 650 MB per side for a 5-1/4" disk.

    CD-R Recorders/Players

    These use media that is the same size as the CD but can be written once and is then read-only like the WORM disk. In many ways, this technology is similar to WORM except that the format is a spiral track like that of a CD rather than circular tracks and sectors like other optical disk formats or hard and diskette drives.

    Although CD-R started out being quite expensive (greater than $10,000 for a recorder), it really was designed as an inexpensive technology and to have total compatibility for reading with CDs and CDROMs. Current prices for multispin (2X, 4X) CD-R recorders are under $500 and dropping. The capacity of a CD-R is the same as a CD - about 650 MB.

    Like the WORM drive, a higher power laser ablates a coating inside the CD-R media. With most, this is a blue-green polymer dye backed by a gold coating. Otherwise, construction of the CD and CD-R media are similar.

    However, since the pits and lands are not as precisely formed as those of a pressed CD whose master was made on a $250,000 laser cutting lath, some CD players or CDROM drives may have tracking or other problems with CD-Rs.

    CD-R recorders and high performance CDROM drives are very similar except:

  • Back to Optical Drive Repair FAQ Table of Contents.

    LaserDisc Players

    If anyone has a really old LaserDisc player (or other optical disk system) they don't use anymore or would prefer not repairing, I may be interested in the entire unit, or at least specific parts from it. Equipment of interest would be the type using a Helium-Neon (HeNe) laser in the optical pickup. In the case of LD players, these are mostly top loaders from the late 1970s through about 1984. Please contact me via the Sci.Electronics.Repair FAQ Email Links Page.

    Considerations when troubleshooting LaserDisc (LD) players

    CD and LD players share much of the same optical technology. Many models will play normal audio CDs as well as LDs. If this is the case, start by determining if a CD will play properly. If it does, then you can be fairly sure that most of the optics and front-end electronics are functional.

    Modern LD players use the same 780 nm laser diodes as CD players. Really old players used Helium-Neon (HeNe) gas lasers resulting in a visible beam at 632.8 nm (orange-red). CAUTION: these use a high voltage power supply. Contact with this probably won't hurt you but will not be pleasant. The high voltage terminals are probably well insulated but it is a good idea to locate them and double check.

    Since most newer LD players also play CDs and some even play DVDs) there will be optical sensors - LED-photodiode pairs aimed at the disc from one or more locations, probably beneath the drawer assembly. (Most also play multiple size LDs as well which also use similar sensing.) If you have the top off for servicing, room lighting may confuse these sensors resulting in all sorts of strange behavior such as attempting to play a CD using the LD spindle! Cover the entire unit with a piece of cardboard or just the holes in the drawer with matt black paper to eliminate the possibility of both electronic and human confusion!

    LD players will generally have one additional servo system compared to CD players - tilt. This adjusts the angle of the pickup with respect to the disc to minimize interference between adjacent tracks. This would result in degradation of the analog video signal. The tilt servo is usually pretty simple using an IR LED emitter and a pair of IR photodiodes detecting the reflection from the laserdisc. If after manually rotating the tilt motor away from the balanced position, the tilt readjusts itself, there is a good chance this it is operating correctly. There is probably a tilt balance adjustment as well but don't touch it unless you have the service manual if possible.

    Spindle motors in LD players are of much higher quality than typical CD players since the spindle must spin continuously at thousands of rpm with the greater mass of the LD as well. Other motors may be similar to those in CD players. Some LD players have two spindles that are selected and moved into position depending on the type of disk being played.

    Due to the mass of LDs, the clamper is even more critical to proper behavior than for CDs. Any slippage and LDs may fail to be recognized.

    There may still be rubber belts that degrade :-).

    Naturally, a video monitor makes an excellent diagnostic tool once it is possible to obtain some output from the LD player. A service manual is almost a must for serious troubleshooting.

    Comparison of semi-antique and modern optical pickups

    Despite great strides in miniaturization, the basic functions that need to be performed by an optical pickup haven't changed since the development of optical recording in the late 1970s. The organization of the optical pickup in the earliest helium neon laser-based LaserDisc players is virtually identical to that of a modern DVD optical pickup. Now, granted, it was a massive casting with dimensions of around 5"x12"x2" compared to 3/4"x1"x0.3" for the modern one in a laptop computer DVD drive. But all the same parts are present in both. See Optical Pickup from HeNe Laser-Based LaserDisc Player. And, yes, that entire assembly moved on roller bearing slides for coarse tracking! Compare this with General Three-Beam Optical Pickup Organization. The only real difference other than size is that instead of moving the objective lens via a coil actuator for fine tracking, there are a pair of X-Y mirror deflectors for this purpose. But the objective lens is still moved by a coil for focus, and the polarizing beamsplitter, three-beam diffraction grating, 1/4 wave waveplate, and photodiode array are separate components. And look at all those adjustments! :) There is a Web site with some information on the first consumer LD player - the Pioneer VP-1000, one of those that used a similar huge pickup. See Pioneer Laser-Optical Videodisc Player Introduction. Another useful LaserDisc Web site is Laserdisc Archive UK, which also includes links to other LaserDisc-related Web sites of interest.

    I recently acquired a Pioneer VP-1000 in working condition. Considering its age of roughly 25 years, this is rather remarkable. Except for a sometimes quirky startup, it operates flawlessly. They used to build these things to last! :)

    (The startup problem is that it doesn't like to reset the pickup quite back to the home location - a gentle push reseats it. This doesn't appear to be a lubrication or similar issue as as the pickup moves freely on its rail and everything is clean with no grease ever being used. But the pickup is buried under circuit boards so getting to it may not be worth the effort.)

    (Update, in 2016, I sold the VP-1000 still in working condition. In fact, based on my experience, the majority of Pioneer HeNe laser-based LD players are still in operating condition 30 to 35 years after their manufacture.)

    A diagram of an even earlier LaserDisc pickup prototype is shown in Optical Path of Early HeNe Laser-Based LaserDisc Prototype. The Wollaston prism is a rather unusual optic which probably never made its way into any commercial unit due to the small separation the polarized beams and its extremely high cost. The Pioneer LaserDisc player, above, used a more conventional polarizing beamsplitter cube (still costly but much less so than the Wollaston), and more recent CD and DVD pickups typically use an even cheaper dielectric coated plate beamsplitter. But otherwise, the designs are very similar. However, some of the newest cost-reduced pickups do away with the polarizing components entirely by offsetting the outgoing and return beams. This probably reduces the performance slightly, but who can argue with the bean counters? :)

    For more information on optical pickup principles of operation and examples of newer technology, see the document: Compact Disc Players and CDROM Drives.

    LaserDisc optical alignment?

    As noted elsewhere, optics don't generally drift except from abuse.

    The following is a further confirmation that optical alignment should not be needed under normal conditions:

    (From: Dave A. Wreski (

    I have been servicing these since they came out. The *only* time I had to do any optical alignments is when some fool decided to mess with the alignments. They do not misalign themselves. In the past the only adjustment we had to do (on Pioneer Laserdisc players) is the 1/4 wave plate which can be done with a scope. All other alignments must be done with a Laser power meter and a polarization adjustment jig from Pioneer. Many dollars!

    If the optics are clean and haven't been maladjusted, your unit is supposed to work. If not, look elsewhere in the electrical alignments or motor problems.

    (From: Sam.)

    I acquired a VP-1000 that indeed did have obviously misaligned optics. (This is a second VP-1000, not the working one described above.) The VP-1000 is a HeNe laser-based unit and the output mirror of the laser tube itself was misaligned, reducing power by 40 percent. The beam out of the objective lens was also clearly asymmetric, indicating misalignment of at least one of the bounce mirrors. This LD player would not even focus, but an electronics problem was likely also present as it did attempt to focus, and was definitely seeing a return beam as the behavior changed if a CD or mirror was placed above the objective lens while it was attempting to focus. But we shall never know, as it's organs have since been harvested. :( :)

    Replacement for Helium-Neon laser tube and power supply components

    Older LaserDisc equipment used a Helium-Neon (HeNe) laser instead of a laser diode. A HeNe laser tube is mounted on the "slider" with a separate high voltage power supply. The tube can wear out or get broken and the power supply can fail. Obtaining an exact replacement from the manufacturer will require a working time machine since these went out of production in the early 1980s. :)

    Note that since the LD standard was designed around the 633 nm wavelength of the HeNe laser, there is some merit to the claim that these gas tube laser-based LD players had better performance than at least early diode laser-based units since the latter were at 780 nm like CD players since they were the first to become economical in the mid-1980s. I do not know if later LD players ever went to red laser diodes as their price came down.

    I (Sam) do have original tubes in healthy condition that were from Pioneer LaserDisc players. I believe these will fit any Pioneer HeNe laser-based unit. I do not know what the other manufacturers use but they are either identical or should be similar enough to be substituted. See Sam's Classified Page for more info.

    However, it should also be possible to substitute a surplus HeNe tube and/or HeNe laser power supply. The tube will have to be of a similar power output (usually around 0.5 to 1 mW) and physical size. It also needs to produce a linearly polarized beam (which eliminates a lot of the common barcode scanner tubes as replacements). If the beam diameter and divergence are similar, it may be possible to get by without any change to the optics as long as the tube is carefully mounted with its output in the same position and orientation as the original. However, some minor optical alignment will likely be required. For this, it is best to have a service manual but even that may not help if special factory jigs are required. However, see the section: Pioneer HeNe laser-based LD player HeNe laser tube replacement and alignment guide. It is suitable for all Pioneer HeNe laser-based LD players and probably most others as well. This may in fact be better since it doesn't require any special costly and unobtainable jigs. But it does assume that the alignment is fairly close to start.

    HeNe laser tubes with power supplies can be had for as little as $25 from various mail order sources but you need to confirm compatibility. It may be possible to compensate for a different beam diameter and/or divergence by adjusting the external optics. However, you can't easily get a non-polarized tube to produce a polarized beam. (It can be done with powerful magnets but this is probably not a viable option inside a cramped LaserDisc player.)

    If a suitable HeNe laser replacement is unavailable, too expensive, or just too mundane, it may be possible to use a diode laser - even a laser pointer - in its place. The beam characteristics would need to be similar with respect to divergence and polarization. A unit with adjustable focus will probably be best to match up divergence. Since, all diode lasers are polarized, that at least, shouldn't be an issue. Apparently, some people have successfully done such a transplant without major problems. But note that some of the optical components are moderately sensitive to wavelength. So, a 650 nm laser diode may be far enough away to cause problems. The most difficulty may arise from devising a suitable mounting arrangement and providing the stable low voltage power needed for the diode laser or pointer. I'd still recommend staying with an HeNe laser if possible but at least, there is an alternative that will keep your prized 1979 LaserDisc player going strong. :)

    And, if that's not enough, alignment can be a real pain, whether it simply after replacing a HeNe laser tube or installing a diode laser. The assembly and alignment procedure in a Pioneer LaserDisc service manual is several pages long and relies on multiple special jigs, none of which of course are still available. But the alignment procedure linked above may be good enough for a tube swap.

    Kenwood LaserDisc clamping problems

    With the larger mass of a LaserDisc compared to a CD, clamping is even more critical. Slipping belts are a common cause of clamping problems.


    I had a problem with my Kenwood machine not locking the disc in place correctly. The disc loading drive belt was slipping, though I couldn't hear it. The replacement was a NEW mechanism that regeared the assembly for slower feed but much more clamping force.

    Magnavox HeNe laser-based LaserDisc players

    Magnavox VCH-8000-CH01 LaserDisc Player

    This is among the earliest LaserDisc players, based of course on a helium-neon laser. Although these were manufactured at least through 1980, their introduction is significantly earlier. The Magnavox VCH-8000 is similar or identical to the Philips VLP600 and VLP700. The difference between the two Philips models is not known.

    And the design of the optical pickup (slider) and entire machine is quite different than that of the Pioneer LD players of similar vintage discussed below. However, it's not clear that these players ever worked properly even when new. They were not reilable and may have had design problems. Unlike early Pioneer HeNe laser-based LD players which are plentiful even in 2007, with many being fully functional, working samples of the VCH-8000 are rare to non-existent. And it appears as though even Magnavox gave up on the design because their second generation LD players are made by Pioneer and are actually LD-1100s inside! :)

    The HeNe laser is in an enclosed laser head made by Philips. The slider optical design is similar to the one in Optical Path of Early HeNe Laser-Based LaserDisc Prototype. Note the unusual double Wallaston beamsplitter prism. Possibly this predates the wide use of the more normal polarizing beamsplitter cubes since it is both more expensive and more difficult to use with the small deviation of the two beams.

    To determine if the HeNe laser is working, remove the single screw securing the latch block attached to the lid at the front but hold it in place. Close the lid and and then lift it so the latch block remains with the main body of the machine. That will fool the interlock into allowing the laser to light when main power is turned on. If the laser is working, there will be a highly divergent red beam emanating from the objective lens which should be on continuously, not flashing or blinking. It's low power and eye-safe. The objective lens may also be moving up and down attempting to focus on a non-existent LD and the spindle platter may also be spinning.

    The low voltage power supply and HeNe laser power supply are on a single large Printed Circuit Board (PCB), with a separate start module. Most of the signal and motor driver electronics are on around 20 tiny plug-in PCBs, each of which is individually shielded. The power supply PCB and backpanel for the tiny PCBs swing out from the main chassis for servicing, so that at least makes sense.

    To get a true feel for the construction, it's best to look at photos. See Magnavox VCH-8000-CH01 LaserDisc Player Gallery for a series of photos provided by David Miyares. The collection from which this was derived may be found at Picasa Magnavox First Production LaserDisc Player.

    The VCH-8000-CH01 I have is in generally good physical condition except for a rotted slider drive belt. I replaced it with a flat belt made by slicing off a piece of a bicycle inner tube. :) The laser seems to work since it definitely does something different depending on whether a valid LD is loaded. It spins up and seems to be happy (even before finding the bad belt) only with an LD in place. Otherwise, it just clicks which is probably focus search and the lens is hitting the stops. And the sound output is just noise.

    At first, I didn't even bother connecting it to a TV expecting nothing to show up. But knowing that the video signal should make the best diagnostic, I first tried what I thought was baseband video into a portable DVD player used as a monitor, but this produced nothing at all. The outputs are not well labeled on the VCH-8000-CH01! Then assuming it was actually RF, I connected my 6 inch color TV, used for testing LD players. There was still nothing useful to report. But after fiddling with the "Chan 3/4" switch and random front panel buttons, it now sometimes produces a distorted but marginally recognizable B/W picture with a CAV LD. (I later determined that the "Aux Video" is actually the baseband signal, but this appeared dead at first.) Getting any recongnizable video at least means the optics and front-end signal circuitry are working, but tracking and/or timebase correction may be faulty. Only when there is a stretch of identical frames (as with a title or the Laser Vision logo) is the picture close to normal, though there is still no color. With a CLV LD, it's still possible to get video, but the picture is much more jumbled and unstable. The only front panel LD motion controls that work beyond turning on their mode LEDs are "Forward Search" and "Reverse Search", and only in a more or less sort of way - Forward may be moving normally, but Reverse goes only a few dozen or a few hundred frames before getting stuck. This may mean the slider motor or its driver is faulty. However, there is audio noise only when the machine thinks it is in Play mode, and just a hint that the noise may actually be an indication of normal audio, if the other issues could be resolved. And, joy of joys, the "Index" button will turn on the chapter or frame number display, which is relatively stable. Although the numbers do jump around somewhat even when the picture is not changing, this means the readout of the LD's digital data is working. If left alone, the location on the LD (based on frame number) sometimes wants to drift backwards, until it ends up eventually at the inner stop (and then the LD takes off like a jet turbine, having lost the video sync signal).

    So far what works:

    What doesn't work:

    Next, I wanted to determine if the tracking and tangential (timebase) deflectors were working properly. These are under a plastic cover accessible from underneath. It requires pulling off a few connectors, 1 screw for the cover, 1 ground connection, and 2 screws to remove the deflector assembly itself. Compared to the deflectors in the Pioneer LD players, these are rather stiff, which could be part of the problem. Gently working them back and forth a bit seemed to loosen them up a bit. I tested with 3 VDC to make sure they responded. The mounting is somewhat keyed, so I don't think optical alignment should have changed much upon replacement.

    Behavior was similar except that every now and then, there would be a bit of color showing up. I then decided to try some careful adjustment of the tracking servo. The little modules are labeled and one had the word "Radial" in it, with 2 pots. Running this thing while being able to access the modules requires lifting it about 2 inches off the table. A set of 4 threaded metal spacers works well enough, though maneuvering it into position isn't fun.

    Turning one of the pots on the Radial module fully clockwise seemed to help some with color showing up almost constantly and much less jitter. However, the other pot had no effect. So, I rather suspect some problem with that module.

    Unfortunately, something else must have been degrading as it was becoming more and more difficult to achieve focus lock when starting an LD, though once lock was successful, it would almost always remain locked indefinitely. But eventually, it became essentially impossible to achieve focus lock, and the machine seemed to become more angry and stared attacking the LDs with the objective lens, resulting in scoring of the LD surface.

    So, that's where things stand.

    My hypothesis at this point is that the main problem is in that tracking and tangential scanner assembly and it needs to be realigned (at the very least). This could possibly be done simply by loading an LD and turning ONLY the laser on with nothing else powered. The LD player could then be placed face-down on a cushioned surface. Then adjust the angle of both mirrors so the beam returns precisely to the photodiode array - somehow. Hopefully, the slider being upside-down would not affect alignment enough to matter - hopefully! :) I couldn't imagine trying to do this with the player in the normal upright position!

    A possibly simpler alternative to physical alignment may be to figure out how to introduce an offset electrically into both axes of the scanner to force each mirror to the proper orientation. If the error is small, this may be all it takes to get it working. But there don't appear to be adjustments pots for at least one of these, as hard as this may be to believe. So a pot or pots may need to be added.

    However, if the mirror suspension is actually rotted and no longer as springy as it needs to be rather than just slightly shifted due to age and neglect, none of this will really help beyond possibly confirming that the scanner is to blame for the demise of these players.

    I did acquire a second sample of the VCH-8000-CH01 with a similar rotted belt, which was just sitting on the bottom cover when it was removed, despite the seller claiming that the machine worked perfectly! :( :) I never could get that one to do anything productive beyond spinning the LD (after replacing the belt) though it may perhaps serve as an organ donor someday.

    I did arrange to borrow the Sams' Photofact for the VH8000 (labeled VDP-1). (I don't know how much difference there is compared to the VCH-8000-CH01 but is sure looks identical and I'm rather surprised that Sams' even bothered with LD players! Perhaps they thought the LD format was the coming wave.) Unfortunately, the resulting copies are rather poor and hard to read as someone tried to save on copying costs. (And, unlike the service manual for the Pioneer VP-1000, there are no instructions on aligning the optics inside the slider.) So I'm still looking for legible service information, either an original Magnavox manual or another Sams' Photofact. If anyone has something available, please contact me via the Sci.Electronics.Repair FAQ Email Links Page.

    Philips Laser disk problems and discussion

    "A friend of mine has a Phillips Laserdisc player that is acting up. What it does is the player will just stop playing in the middle of the movie, usually in the same spot."

    (From: Douglas W. Jefferys (

    How old is the player? I've worked on the Philips 22VP931 and seen similar things. This is an ancient (ca. 1982) industrial player with a tendency for the radial and tangential mirrors to jam in their servos. (The glue that holds the magnets behind the mirrors weakens with age. If a magnet detaches, the mirror jams solid, but the magnets can also migrate outwards and cause sticky behavior).

    If it's an older player, it's *possible* that it's in the early stages of the same failure mode. (That said, all the 22VP931s I've seen that have this failure have had *solid* jams on at least one of the mirrors, so I think it's an all-or-nothing thing.)

    Anyways, after fixing the servos (a nightmare - it's a good thing I had help from a knowledgeable source about what to expect when I went into the guts of the thing :-), I did an eyeball alignment (power *OFF*, machine unplugged, a double-check that the power is off and the machine unplugged, and look down through the objective and see if you can see down the entire beam path) and got the same results you did. Worked fine on the early portion of the disk, but slowly screws up later on. High-speed seeks worked marginally early on, and not at all on later portions of the disk.

    An examination of the player while playing showed that one of the mirrors was near the limit of its range of movement at the point when the video started freezing up.

    NOTE: I'd strongly recommend *against* looking at the mirrors in operation unless it's either a visible-beam system or you have goggles opaque to the laser's frequency. I was willing to be somewhat stupid because it was a visible-beam system, and I still used a piece of paper to ensure my head was nowhere near the areas where bits of beam were leaking from the player. I wouldn't have even fantasized about attempting this with an IR beam.

    About three hours and umpteen incremental adjustments of the optical head's alignment screws (which I had to remove and thereby misalign when fixing the servos), and the thing was working fine.


    1. Check to ensure the tangential/radial mirrors move freely.

    2. Check optical alignment on early portion of disk and 'stuck' portion of disk. Preferably with an optical alignment tool, but if you've got goggles or a visible-beam system and more balls than brains, you can *carefully* look at the mirrors when the disk is playing and use that as a guess as to which way to tweak the mirrors.

    One final note: Some of the alignment things can be "one-way" adjustments, and anything on the optical path is vulnerable to scratches. I'd strongly advise trying to find the service manual before attempting any modifications.

    If you have contacts with professional fixers, I'd also suggest you bounce your ideas off of them before proceeding. When hacking LD players, you're always one mistake away from owning a very expensive pile of spare parts.

    Pioneer HeNe laser-based LaserDisc players

    There were introduced around 1979 and were the first were probably the most popular of the early LD players. All used a very similar optical pickup (more below) but the so-called "2nd generation" players like the LD-660 and LD-1100 greatly simplified the electronics and overall construction compared to the original VP-1000.

    Basic information as well as links to specific models can be found at:

    User and service manuals, specifications, interface guides, and other more detailed infromation for selected models:

    If anyone has original service manuals or high quality scans of service manuals for Pioneer HeNe laser-based LaserDisc players, please contact me via the Sci.Electronics.Repair FAQ Email Links Page.

    Pioneer PR-7820 LaserDisc Player

    This industrial player was used in GM showrooms to introduced it's automobiles and was the original player (under the designation Pioneer Model 3) used in thousands of Dragon's Lair and Space Ace arcade video games. Dating from 1979, it was the first and only LD player to fully conform to the DiscoVision specifications.

    The PR-7820 is unique among HeNe laser-based LD players to mount the pickup above the disc. Thus, the disc must be placed on the spindle upside-down with the label for the side being played underneath. Unlike other LD players, the disc gets clamped to the spindle by a manual spring-loaded mechanism, and it's quite possible to destroy the disc and who knows what else if one forgets to lock it in place and the disc spins up and wobbles. A part of that clamp is a rubber sleeve, and on a unit I've seen, that had decomposed into a black gummy oily mess. I'll have to jump into my time machine and go order a replacement. :)

    The optical pickup of the PR-7820 is very similar to those in the other Pioneer HeNe laser-based LD players, but in this one it doesn't move and so can't be called a "slider". Rather, it is bolted down under a metal shield which is under the plastic cover on the right side of the player. See Pioneer PR-7820 LaserDisc Player with Optics Covers Removed and the closeup in Optical Pickup of Pioneer PR-7820 LaserDisc Player. Note how it is *wonderfully* accessible for service so that optical alignment can be performed without subjecting the player or the human to extraordinary acrobatic feats. The laser and optics are functionally identical to those in the other players, except for the lack of a pivoting tangential mirror - there is a third fixed mirror in its place. This is shown in Closeup of Tracking Galvo and Bounce Mirror on Pioneer PR-7820 Optical Pickup. The tracking mirror assembly is visible near the top center of the photo while fixed bounce mirror is partially hidden by the bracket above the ballast resistor. Tangential (time-base) correction was performed electronically, a feature abandoned in favor of the second pivoting mirror used on all subsequent HeNe laser-based players and the first few years of diode laser-based players. Solid state time-base correction was not reintroduced by Pioneer until the LD-909 several years later.

    And, it has a tiny light bulb (visible in the photo) next to the HeNe laser tube, presumably to help it to start in the dark enclosure. The VP-1000 also has this "feature" but it disappeared in later models.

    The spindle is mounted on a slider mechanism and of course the motor spins counterclockwise since the disc is upside-down. This also means the LD labels must be interpreted as being on the wrong side. :)

    The PR-7820 has a 24 pin Centronics control connector as well as an external sync input so the video can be locked to an external source. These are not found on any of the players designed for the consumer market.

    Additional PR-7820 information can be found at:

    I'm not aware of any free service manuals or schematics for the PR-7820, but there is programming and related information available from the Dragon's Lair Pioneer LaserDisc Player Tech Center. There is an electrical adjustment procedure there as well, but it assumes the use of special test LDs and makes a lot of assumptions, so I'm not really sure how generally useful it really is.

    Not realizing how the clamp mechanism worked, or that the rubber had oozed, I tried to play a disc on the PR-7820 I have. It made a horrible grinding noise as it moved into playing position. The resulting scuffing on the LD outer portion of the LD can just be seen in the photo above. It's a garbage LD but I may try out one of the CD/DVD repair products to see if that helps. One company offered to send me free samples. Or perhaps toothpaste. The rotted rubber mess was cleaned up with generous quantities of rubbing alcohol and paper towels. Then some bits of bicycle inner tube were used as a stopgap filler until the replacement rubber sleeve ordered during my temporal trip to 1982 arrives. :) The LD clamps down securely. I used a fiber-optic illuminator to light up the area under the pickup to inspect for anything that might be protruding and interfering with the disc. There was nothing. So, I risked messing up the already damaged LD and tried to play it again. It now apparently doesn't rub against anything, though this machine has more mechanical noise than any other I've seen. It now will accept a disc and sort of play it. Normal tracking, scan, slow, step, and frame display all work flawlessly. The video and audio were present, but saying they were horrible would be a complement. At first I figured there must be something faulty, or way misadjusted in the signal circuits. It was conceivable that someone had been inside before twiddling pots. But if you just wanted to watch the disc/spindle assembly move back and forth, it worked great! :) Then, on a hunch, I connected the baseband video and audio outputs to a monitor. The picture and sound quality there were fine. So, the problem had to be in the RF modulator, but they don't go bad much. However, jiggling the Chan 3/4 switch fixed it. Dirty switch. (Locating the switch was the hardest part as it's not exactly near anything relevant.) Hard to imagine, the machine is only about 27 years old and the switch probably hasn't been touched in 27 years. :)

    Then I spent 2 hours trying to determine why the LD spindle assembly was hitting something and getting stuck periodically, usually just as it seemed to be working properly. Unfortunately, gaining access to the area of the spindle motor slider mechanism requires removing many screws and the main PCBs and card cage. And even then, it's not really accessible, except perhaps with a bore scope, without taking apart much more. But apparently, someone (who shall remain nameless) dropped a screw inside and never fished it out. :( :-) It turned out to between the moving spindle motor assembly and frame so none of that aggravating disassembly was really needed. The screw simply decided to appear while poking around. At least I hope that's all it was, but so far, that problem has not reoccurred.

    As it turns out, as of late 2009, it was still possible to order a replacement for the rotten part from Pioneer - for only $43 + shipping! Go to PR-7820 Rubber Plate Assembly. It is not known if they still make them, or travel back to 1982 for each order. But, it is likely that any part made in the early 1980s would be just as rotted after 25+ years so these must not be NOS (New Old Stock). Thanks but no thanks. I'll just glue a slice from a bicycle inner tube to the existing de-gooed plate. :)

    Pioneer VP-1000 LaserDisc player

    This is one of the earliest, perhaps the earliest Pioneer consumer LaserDisc player, introduced around 1980. (The PR-7820 came before it but was probably not aimed at the consumer market.) The VP-1000 uses a 1 mW HeNe laser tube (about 10 inches long) on a similarly huge "slider" - which is what Pioneer calls the moving optical pickup of the LaserDisc player.

    Additional VP-1000 information can be found at:

    The VP-1000 uses an optical arrangement like the one shown in Optical Pickup from HeNe Laser-Based LaserDisc Player. The one in the VP-1000 differs very slightly physically but is optically and functionally the same. (The main difference being that the baseplate for the pickup in the VP-1000 ends at the left edge of the X-Y deflector so the laser tube sticks out the left side. Perhaps too many were getting smashed.) It runs on a roller track, moved by a small DC gear-motor. The functions implemented by this assembly are identical to those in CD or DVD pickups except that (1) this one is HUGE in comparison - perhaps a ratio of 100:1 in volume and (2) there is one additional function - tangential correction - which is unique to LaserDisc system. For a description and diagrams of CD and DVD pickup operation, see the document: Compact Disc Players and CDROM Drives. Tangential correction compensates for slight short term variations in disc rotation speed which would result in time-base errors in the video signal which would cause both horizontal jitter and color noise. So, in addition to the focus and tracking servos, there is also an additional one for tangential correction which drives a mirror that can move the spot along - or tangential - to the track. Later LaserDisc players performed this function digitally but in the first few years of LaserDisc, it was done in this manner - which worked quite well.

    The HeNe laser is rated around 1 mW but may produce up to 1.6 mW or more. As with all of these, it is linearly polarized. Both NEC GLT-165 and Toshiba LG-3217 tubes were used and are more or less interchangeable. The the laser runs as long as main power is on (VP-1000 only), so it's probably best to turn off the machine if it's not going to be used for awhile. A mechnical shutter blocks the beam when the lid is open to prevent accidental exposure to the very powerful laser. :)

    And, in case you were wondering, the VP-1000 does use a microprocessor for control. It appears to be a two chip set consisting of a UD6002B (or UD4002 or UD6002A) "Micro Processor" and UD4001 "Data Processor", both 8 bit, located on PCBs under the control panel. And, you can even still buy replacements from someone on the Web for around $100! :)

    I picked up a more or less working VP-1000 on eBay. LaserDisc players - especially vintage LaserDisc players - are dirt cheap at this point since everyone wants DVD or Blu-ray. It even came with 7 movies. :) But the shipping is still costly since early LaserDisc players weigh in at 40 to 50 pounds. The unit was basically working, except that it wouldn't always start up - would decide to keep popping the lid (meaning it didn't like the disc or thought there was no disc in place) rather than spinning the disc. Pushing the pickup to the inner stop usually got it going - the pickup didn't reset quite to the home position. Once it would spin, playback was flawless. All functions worked and the disc could be scanned from end to end. I first cleaned the lens and that seemed to make a slight improvement. I then adjusted the setting of the inner limit switch - it was definitely not where it was supposed to be according to the service manual. Getting to it requires removing the bottom cover. At that point, a long hex wrench might be able to get to the adjustment screw through a hole on the side but there is no way to determine the correct setting. So, it's better to turn the entire player over (supported on the sides only by Styrofoam blocks) and then removing the circuit board with the small shielded cover (4 screws for the PCB and 1 screw to enable the center bar to be pushed slightly to the side so the PCB could be removed from the frame). The slider can be freed from the gear drive by gently pushing the slider motor (accessible through a hole in the PCB above it) away from the slider. The hex adjustment screw changes the angle of the lever that operates a microswitch. It should go on (listen for a click) when the slider is about 1 mm from the mechanical stop, which is also when the lens cover (viewed on top) is about 1 mm from the left end of the plastic cutout with the space between the lens over and plastic cutout being approximately the same around the semicircle.

    Startup now seems to be reliable. But the adjustment may just be covering up some other problem since I don't see how it could fail to start up if the pickup were at the wrong location on the disc. The player's microcomputer doesn't know that until it spins and tries to sync with the disc. But it would just try to focus a couple times without spinning, give up, and pop the lid. So, perhaps the laser is weak or slightly misaligned despite the excellent video performance, or perhaps the focus servo needs adjustment. The thing was sent without engaging the shipping lock screw (which is missing entirely). It's there to prevent the pickup from banging around so who knows what might have happened. And on these old LaserDisc players where the slider/optical pickup weighs a couple pounds and can disengage from the gear-motor (by design) if enough force is applied, it can not only slam into the end stops but also damage the plastic gears. Having said that, I rather suspect old age, use, and possible prior attempts at repair for the problems rather than shipping damage.

    A second VP-1000 (also eBay) would not achieve focus lock and had obvious optical alignment problems and low laser power, though the actual cause of the failure to focus might have been electronic in nature since its behavior did change if an LD was present and thus was seeing a return signal. The output mirror of the laser tube itself was misaligned - that can happen to any HeNe laser after many power cycles - but at least one of the bounce mirrors was also misaligned as the output beam from the objective lens was asymmetric. Aligning the laser tube had no effect on behavior even though the optical power from the objective lens increased by at least 50 percent. That unit has now been disassembled so its optical pickup can be used as a demo unit. It's not worth attempting to repair a 25 year old LD player when so many are available for next to nothing on eBay! :) In fact, the laser tube and optics are worth more than the intact player these days.

    The only schematic available (free) on-line related to the VP-1000 is for the HeNe laser power supply. See HeNe Laser Power Supply from LaserDisc Player 2.

    Complete original Service manuals for the VP-1000 and other vintage LaserDisc players are available from places like Stereo Manuals should you have the irresistible urge to repair your player or are simply curious about how it works.

    Pioneer LD-660 LaserDisc player

    The Pioneer LD-660 came out a year or two after the VP-1000 and is considered "2nd generation" (and the construction of all of these is very similar). The LD-660 is a bare bones machine with only the most essential functions. So index search and time/chapter/frame display are not present. And there is no remote control. The laser and optical arrangement is almost identical to that of the VP-1000, but the under-chassis layout has been greatly simplified. See Below Deck View of Second Generation Pioneer LaserDisc Player. This photo shows everything in place except for a black plastic dust cover that normally encloses the laser tube and optics on the slider, removed for the photo. The transformer for both the low voltage and high voltage power supplies is at the lower left with the LV regulator PCB above it and the HeNe laser power supply HV PCB on its right. The gear driven pot above it is used to adjust the servo gains depending on slider position. The fan blades are on the main spindle motor shaft.

    A single large circuit board has most of the electronics and adjustments and swings down for service. A couple of smaller circuit boards and the LV and HV power supplies are separate. However, unlike the VP-1000 where the adjustments were all labeled with their functions and could be accessed from the side after removing the bottom cover, those on the LD-660 are scattered around the large PCB and are not labeled except with part numbers like "VR7".

    The LD-660 optical pickup ("slider") is shown in Optical Pickup from HeNe Laser-Based LaserDisc Player. It is functionally similar to that of the VP-1000 and other Pioneer LD players made in the early 1980s.

    Both NEC GLT-165 and Toshiba LG-3217 HeNe laser tubes were used and are more or less interchangeable. The laser tube is turned on only when actually playing a disc, unlike the VP-1000 where it runs whenever main power is on. Thus, the tube in the LD-660 should have a longer useful life.

    As noted, the LD-660 lacks the advanced functions of many other LD players. But this is somewhat of a benefit since the LD-660 will happily play almost any LaserDisc ever produced. It doesn't care what it sees when starting, simply initiating play at the inner stop. It also lacks a remote control but has the required basic functions on the front panel including scan, slow, and single frame (the latter two in CAV mode only, as with most of these that lack a digital frame store). It also has an indicator on the front panel of play location on the LaserDisc - an LED whose location on a 0 to 10 scale is mechanically linked to that of the slider. While crude, I miss this on other Pioneer models which use an on-screen display of chapter/frame or time which must be turned on by the remote.

    Additional LD-660 information can be found at:

    There was also an LD-600, but that may simply have been the same model sold only in Japan.

    The only schematic available (free) on-line specifically for the LD-660 is of the HeNe laser power supply. See HeNe Laser Power Supply from LaserDisc Player 1.

    Note that this schematic combines the circuitry of the HeNe laser power supply PCB, power transformer, and relevant parts of the required low voltage DC power supplies, located elsewhere. The wire just to the right of C16 is the connection from the separate low voltage DC power supply (brown wire for plus and black wire for ground) and the input "I" (which must be grounded to turn on the laser) is a red wire.

    Complete original Service manuals for the LD-660 and other vintage LaserDisc players are available from places like Stereo Manuals should you have the irresistible urge to repair your player or are simply curious about how it works.

    However, since the LD-660 is very similar to the LD-1100, see the next section for links to additional technical information that should apply.

    Pioneer LD-1100 LaserDisc player

    The Pioneer LD-1100 was a "2nd generation" high-end machine that looks very similar to the LD-660 but has all the features (chapter/frame display, search, etc.) of the VP-1000 (but some are only on the remote). The was a specific remote for the LD-1100, but the RU-1000 for the VP-1000 works fine. Early versions supposedly had optics that were inferior compared to the LD-660 but this was fixed in later production. I don't know the reason unless Pioneer tried to cuts costs (and corners) when going to the 2nd generation players, and found out the hard way that this was a bad idea.

    The physical layout of the LD-1100 is the same as that of the LD-660 except that the main circuit board is a bit larger to accomodate circuitry for the additional functions.

    Additional LD-1100 information can be found at:

    User and service manuals for the LD-1100 may be found at the Dragon's Lair Pioneer LaserDisc Player Tech Center. The scan quality of the technical information (diagrams and schematics) is marginal but that's better than nothing.

    See the section on the LD-660, above, for additional technical details.

    There was also an LD-1000 for the Japanese market which is supposed to be virtually identical. Some versions had a transparent window in the cover to view the LD.

    Pioneer LD-V1000 LaserDisc player

    This is another 2nd generation player. It can only be controlled via a computer interface. There are no front panel controls, though apparently a special service remote may be used. The LD-V1000 only plays CAV disc (so it's pretty useless for movis) and was part of a number of arcade video games including Space ACE and Dragon's Lair. (There was also an LD-V1001, a 100 VAC model for the Japanese market.)

    The construction is generallyy along the same lines as the LD-660 and LD-1100 and the slider looks the same, though there may be subtle differences not visible to the naked eye as the LD-V1000's performance including search speed and error recovery is superior. One that I am aware of is that the motor that moves the slider is geared to be several times faster in the LD-V1000 than in any of the other Pioneer HeNe laser-based LD players. The LD-V1000 will supposedly search to any frame on a CAV disc in under 3 seconds. Also unlike the VP-1000 and most, if not all other Pioneer LD players of this era which used a high quality DC brush-type motor, the LD-V1000 has an electronically commutated brushless DC motor with a PA-2021 controller chip. However, the actual multiphase drivers are on the mainbaord as the motor will not run stand-alone. Since the LD-V1000 only plays CAV LDs, it's not rate of acceleration that would be the reason for this, but probably either reliability or constancy of rotation speed.

    The HeNe laser power supply is also the same except that on the one sample of an LD-V1000 I've seen, the lid interlock is a switch between the HV filter capacitor positive output and the regulator transistor. This also shows up in the service manual. The other 2nd generation player HeNe laser power supplies I've seen lacked this feature, probably using the enable input indirectly as the interlock via a low voltage signal. Perhaps, it's just that the LD-V1000 is a generally later design than the others.

    Additional LD-V1000 information can be found at:

    User and service manuals, schematics, and an interface guide for the LD-V1000 may be found at the Dragon's Lair Pioneer LaserDisc Player Tech Center. The scan quality of the technical information (diagrams and schematics) is marginal but that's better than nothing.

    Comments on Pioneer PR-8210

    (Portions from: Dave A. Wreski (

    The PR-8210 service manual is 120 pages long. This is not an easy unit to work on. It is the very first industrial video disk player that Pioneer made. All of the GM dealers had them when they first came out and I have seen them for sale in most flee markets for around $50.00.

    These are built like a tank and use a HeNe laser tube and a bunch of discrete optics that are very hard to align properly without the manual.

    (From: Sam.)

    The PR-8210 is very similar to other "2nd generation" Pioneer LD players. So, it's probably no easier or harder to repair or align. See the sections on these, above.

    Known problems with Pioneer 2nd generation LD players

    Various sources describe the performance of the LD-1100 to be inferior to that of the more basic LD-660 due to some problems with the original slider optics. I have not been able to actually verify these claims nor demonstrate them with any of these players I own.

    There is, however, an annoying quirk that seems to be present to a greater or lesser extent with all LD-660s and LD-1100s: An acoustic whine around 650 Hz (the E above the C above middle C or E5) that appears for a few minutes about 5 to 15 minutes into CLV discs. The whine is not present in the audio signal and is probably due to some sympathetic vibration of sheet metal or plastic parts in the player, though the source is not obvious from external poking or prodding, and cannot be reduced significantly by covering the top of the player with sound deadening material. These LD players are not exactly what one would call quiet due to the high disc rotation speed, but the whine stands out from the low frequency vibration and whoosh of the airflow over the disc since it's close to a pure tone, and can be quite annoying during a quiet scene in a quiet room. Units manufactured in 1981 and 1984 both suffer from this problem, though possibly the loudness is slightly reduced in those from 1984.

    If you have any more info on these issues, or a cure for the latter short of enclosing the unit in an acoustic shield placing it in a closet, please contact me via the Sci.Electronics.Repair FAQ Email Links Page.

    Quick check of optical alignment

    Optical alignment is rarely a problem even with 25 year old LD players. However, it's easy to do a simple visual test to check for obvious problems. To do this, it's necessary to observe the spot projected by the objective lens and thus the interlock to prevent laser output with the lid open has to be defeated.

    Then, observe the red spot on a white card a couple inches from the objective lens. There will be many parallel lines due to the effects of the grating used for tracking and there may be some mottling and splotches from dirt on the optics, but the spot should be fairly circular and symmetric and brightest in the center. If it is very asymmetric, alignment may be the cause of any number of play problems, or an inability to even achieve focus lock. One or more of the optical components may be misaligned, or the mirrors of the laser tube itself may be misaligned (NEC GLT-165 or other tubes with metal mirror mounts, not the Toshiba LG-3217 or other all-glass tubes).

    Dirty slider pot causing erratic behavior

    Second generation Pioneer LD players (and possibly some others) have a pot that is geared to the position of the slider (optical pickup). This controls the gain of the tracking and other servo systems. Should this pot become dirty and noisy (usually due to the player being a long time in storage), it's possible for there to be various effects in playback at random times. I only have annecdotal evidence to support this but others have cited a noisy pot as the cause of a variety of annoying and somewhat random symptoms.

    Cleaning the pot is easy enough: Unplug the LD player and set it upside-down on a soft surface and remove the bottom cover (6 to 8 screws). The pot is next to the high voltage PCB more or less opposite the trigger transformer. After cleaning, the pot will need to be exercised. Put match marks (ink or paint) on the large gear and rack, or on the large gear and bracket (but don't move the slider), as the gear "timing" is important. Spray control cleaner into the open slot in the pot, lift up on the pot to disengage the gear from the rack, and rotate the gear back and forth a few times. Then make sure the match marks line up before re-engaging the gear and rack. However, if you do mess up and lose track of the relationship, it looks like the range of slider movement just about covers the total pot rotation so just center it wihin this range and then make sure the slider motion is limited by the end-stops, not the pot. :-)

    Cleaning should suffice - after all, this pot doesn't get that much of a workout. If problems persist, they most likely have some other cause. However, where replacement is needed, it's a common linear taper, 10K ohm pot labeled on the back.

    HeNe laser-based LD player HeNe laser tube replacement and alignment guide

    This is an elaboration of the procedure found at Re-charge the lasertube on a LD-V1000. I have tried to add clarifications where needed since not everything there is, shall we say, perfectly clear. :) In addition, the diagram referenced on that page is missing so refer to Optical Pickup from HeNe Laser-Based LaserDisc Player. (In the diagram, the turning mirrors at the lower right and upper right correspond to the 1st and 2nd fixed mirrors mentioned in the text. And up and down in the photo correspond to up and down in the text.) Print out the Cinematronics page as well since there are some little drawings within the text that may help.

    I am rather suspect of some of the steps in the Cinematronics procedure. For one thing, adjustments of anything beyond fixed mirrors #1 and #2 should NOT be needed if only the tube is to be swapped. The optical path from the tube can be completely aligned using only those two sets of adjustments. In addition, one of the steps (specifically, aligning the beam to the photodiode) may be highly dependent on exactly where the objective lens is positioned relative to the disc. I'm not sure this can be predicted. So, I have included a simplified procedure in addition to the lengthy one. I am also not convinced anyone has actually performed this successfully!

    The following applies to all 2nd Generation Pioneer HeNe laser-based LD players. It also applied to the Pioneer VP-1000 except to the extent that the laser assembly on the slider is more complex as it also includes the HV multiplier block so tube swapping requires some additional steps (which should be self evident). Also, the laser runs all the time power is on so the additional step of enabling it is not needed for the VP-1000.

    CAUTION: Attempt this only if you are really desperate! If the old laser is still working, don't fix it! Your problems are probably caused by something else. Furthermore, working LD players are readily available on eBay. At any given time, they will likely include those compatible with arcade games like Dragon's Lair, as well other HeNe laser-based models as well as all the newer ones - sometimes for less (including shipping) than you'd pay for a even a surplus HeNe laser tube (let alone a new tube), not to mention the loss of your hair and sanity attempting to perform these procedures. :)

    Common steps:

    CAUTION: DO NOT even think about turning any screws unless specifically instructed to do so. It's very easy to make things much worse, possibly terminally worse.

    Initial preparation:

    1. Place a clean LaserDisc in the player and close the lid. It doesn't matter what type - CAV or CLV - for initial alignment as it is only going to be used for its reflection. But for final adjustments, a CAV disc should be used so you might as well put that in now. Allow it to spin up (if possible) just to make sure its seated properly. Then power down and turn power off. During any of the following, DO NOT hit PLAY unless the player is in the normal orientation, feet down! The disc can fly off and and then all heck breaks loose. :( :)

    2. Flip the player over (upside-down) and remove the 6 to 8 screws securing the bottom cover. Remove cover. (The Cinematronics procedure doesn't explicitly indicate whether to have the player flipped on its top (upside-down) or on its back side :), but it kind of implies the side by references to up and down for the locations of optical components. But the flipped over position would seem to be much more stable.

    3. Remove the 4 screws securing the main PCB and flip it up.

    4. Remove the 2 screws securing the slider cover and gently remove the cover taking care not to disturb the (likely rotted) foam more than necessary. Note that there may also be pieces of black tape sealing the cover and these will have to be carefully peeled off or sliced with a razor blade as well.

    All subsequent steps may be performed with the player in any position. However, if electrical adjustments of tracking and/or tangential servos are required after completion, the player should be placed in the normal operating position for at least two hours to allow the deflector mirror mounts to regain their normal "set". (I don't know how critical this is but the VP-1000 manual makes a point about it.)

    Testing the old tube:

    1. For 2nd generation players like the LD-1100, LD-660, PR-8210, and LD-V1000, the laser needs to be enabled in addition to applying power to turn on. With power off, attach a jumper from the Enable input on the HeNe laser power supply PCB (pin 12, probably a red wire) to ground (black wires or chassis) and then power up the LD player. The laser should come on instantly and stay on. If the tube does not light or flashes, it or the power supply may be bad, or the HV connector may need to be reseated. Note that HeNe laser tubes do not generally fail suddenly (unless they are smashed!), so if that's what happened, look elsewhere for the cause before considering a tube replacement.

    2. If the old tube is a NEC GLT-165 and still works but is weak as determined either with a laser power meter or because the player had become increasingly susceptible to mistracking, dropouts, or increased video and audio noise, this may be due to the alignment of the tube's mirrors (not the slider optics) having changed after many power cycles. It may be possible to realign its mirrors without removing the tube. However, this is not something to be attempted by the novice unless you have nothing to lose (which is likely the case here). (The mirrors of the all-glass Toshiba LG-3217 cannot be realigned.) Instructions for aligning the tube mirrors is beyond the scope of this procedure. See the chapter: "HeNe Laser Testing, Adjustment, Repair" of "Sam's Laser FAQ" for details. But checking the alignment is straightforward and low risk.

    3. Assuming the tube stays lit, place a white business card or something similar in between the two fixed mirrors so that the laser spot is visible. A laser power meter is desirable for this test but just eyeballing the brightness of the spot should work.

    4. Use an insulated tool like a wooden stick or toothbrush handle to *gently* press sideways on the gray rubber boot near the output end of the tube. The brightness of the spot will change with only modest force. Try this at 4 to 8 locations spaced around the tube. For a properly aligned tube, the brightness should always decrease with increasing force. If there are orientations where it increases noticeably, then the tube's mirror(s) need realignment. WARNING: The output end of the tube has the high voltage on it, thus the insulated tool!

    Where the tube still lases but is weak but that the player still kind of works, though perhaps with reduced signal to noise ratio or other play problems, the alignment procedure after tube replacement can be simplified considerably. Go directly to the "Simplified alignment procedure", below.

    Full alignment procedure:

    Attempt this where the original tube doesn't work or its mirrors are misaligned, or someone has turned every adjustment screw in sight!

    Replacing the tube:

    1. Power off and unplug the LD player from the wall.

    2. Before removing the old tube, note its approximate orientation and the distance from the output end to the first fixed mirror.

    3. Remove and save the two inboard screws holding the laser tube. Carefully bend the two clamps up so the tube can be freed. If this is not possible, the nylon rack gear will have to be removed to provide access to the two outboard screws.

    4. Unplug the HV connector to the tube.

    5. Transfer the wiring, ballast resistor, insulators, and pads to the new tube in exactly the same position as on the old tube. Make sure the wiring is done exactly the same. If wired with reverse polarity, the replacement tube may appear to work but will be ruined in a few minutes.

    6. Place the new tube assembly back in position at the same distance from the first fixed mirror and at approximately the same orientation. Install the mounting screws to hold the tube in place but DO NOT tighten them just yet. Install the HV plug.

    7. Power up the LD player. The laser should come on instantly and stay on.

    The next step sets the polarization axis of the tube. A laser power meter is desirable but this can certainly be done by eye.

    1. Move the white card to a position in front of the polarizing beam splitter cube (away from the silver electronics shield).

    2. Carefully rotate the tube so that the brightness of the spot is a minimum. Tighten the outboard screws fully (if these were disturbed). Tighten the in board screws to hold the tube securely but unless they seat against the metal, don't over-tighten and crack the tube! Make sure the tube can't be easily rotated accidentally.

    3. Recheck the polarization to assure it didn't change. Readjust if needed.

    Now on to alignment:

    1. Remove the diverging lens assembly. This requires taking out 2 screws.

    2. Place a white card to the left of the 1/4 wave plate. There should be 3 dots in a vertical row, the center one being the brightest. If only 2 dots are present, outgoing alignment needs to be adjusted using the hex screws on the sides of fixed mirror #2.

    3. Also, there should be a faint line running through the tree dots. If it is curved, correct this using the screws on the top and bottom of fixed mirror #2.

    4. Remove the white card and check the beam hitting the tracking mirror (first of the deflectors). If it is not approximately centered, loosed the screw holding the tracking mirror to the casting and adjust its position. (Unless the tracking and/or tangential adjustments had been messed up, it doesn't seem likely that this step should be needed. --- Sam.)

    5. To check the return beam (from the disc), look at where it hits the left side of the 1/4 wave plate. It should be centered. If it is not, loosen the tracking mirror screw slightly to move the beam up and down. Do the same with the tangential mirror to move the beam from side to side. (To get to the tangential mirror locking screw, move the slider to the end-stop and use a stubby Philips head screwdriver.) Try not to have both screws loosened at the same time and take care not to allow the two mirrors to contact each-other. (Unless the tracking and/or tangential adjustments had been messed up, it doesn't seem likely that either of these steps should be needed. --- Sam.)

    6. Next, the return beam alignment needs to be fine-tuned going to the photodiode. Move the slider back to the home or park position. Place a small piece of paper against the side of the prism next to the photodiode shield. The return beam should appear as a spiral or bullseye pattern on the paper. As the disc is rotated (by slowly rotating the motor fan), the pattern will collapse and expand, but the rings should look fairly symmetric, not offset to one side or the other. Re-adjust the tracking and tangential mirrors to correct.

    7. Replace the diverging lens and adjust its position using the two adjustment screws to center the beam on the right side of the 1/4 wave plate.

    8. Turn the player off, remove the jumpers from pin 12 of the HV PCB and ground. (I assume you're supposed to flip the player upright at this point though it isn't mentioned.)

    9. The rest is adjusting the position of the diverging lens and photodiode for maximum open-loop tracking signal. (Just a suggestions: If the disc spins up and achieves focus lock immediately, scan over to around track 14,400 on a CAV disc, and do the adjustments there. The reason is that if focus lock is lost while the disc is spinning, the player won't immediately shut down, but will continue to try to focus with the objective lens popping up and down, resulting in an easier alignment. Perform the final adjustments only after the player had been in the normal position for a couple of hours.

    Simplified alignment procedure:

    This applies where the old tube still lases and its mirrors are well aligned, and the LD player works somewhat, but possibly with play problems. Start by going through the first 8 steps, above.


    1. Power up the laser. Attach a small piece of the sticky part of a Post-It note to fixed mirror #2. (The Post-It note adhesive won't harm the mirror coating.) Use a felt tip marker to identify the *exact* point on the paper where the beam hits. This will be your target for aiming the new tube so the more accurately this is done, the better will be the ultimate alignment. DO NOT let this paper move until the new tube is fastened down with its polarization axis set and its beam hitting the exact same spot.

    Replacing the tube

    1. Power off and unplug the LD player from the wall.

    2. Before removing the old tube, note its approximate orientation and the distance from the output end to the first fixed mirror.

    3. Remove and save the two inboard screws holding the laser tube. Carefully bend the two clamps up so the tube can be freed. If this is not possible, the nylon rack gear will have to be removed to provide access to the two outboard screws.

    4. Unplug the HV connector to the tube.

    5. Transfer the wiring, ballast resistor, insulators, and pads to the new tube in exactly the same position as on the old tube. Make sure the wiring is done exactly the same. If wired with reverse polarity, the replacement tube may appear to work but will be ruined in a few minutes.

    6. Place the new tube assembly in position at the same distance from the first fixed mirror and at approximately the same orientation. Install the mounting screws to hold the tube in place but DO NOT tighten them just yet. Install the HV plug.

    7. Power up the LD player. The laser should come on instantly and stay on.

    8. Since the beam can't reach the polarizing beam splitter cube due to the Post-It, some other means will have to be used to adjust the tube orientation so the polarization is horizontal. This can be done with a polarizing filter whose orientation has been accurately determined, or another cube. Or, for LG-3217s, the internal Brewster plate can be seen so set the tube that is exactly horizontal. Then tighten down the tube so it can't move but not so tight that it gets crunched. :( :) Double check the polarization.

    Fixed mirror alignment

    1. Adjust fixed mirror #1 (both axes) until the beam precisely hits the target point on the Post-It. Take your time to do this accurately.

    2. Remove the Post-It. The expanded beam should be roughly centered where it enters the objective lens, and strong and symmetric. If not, fine-tune fixed mirror #2 (both axes). Only very small adjustments should be needed. Of course, this assumes that the optics were aligned with the expanded beam centered in the objective lens with the old tube. One can hope. :)

    3. If your original spot location was accurate on the Post-It and the original alignment was correct, nothing more should be required. If not, some very slight adjustments to both mirrors will be necessary.

    4. Button up the player, place it in the normal position, turn on power, and hit PLAY. Hopefully, alignment is now close enough to achieve focus lock. If so, final optical alignment can be done by maximizing the open loop tracking signal with very small adjustments to fixed mirrors #1 and #2 ONLY. Wait until the player has been in the normal position for a couple of hours before doing the final adjustments. There should be no need to touch any other optical adjustments or electrical adjustments.

    Cleaning/repairing the RU-1000 and CU-1100 remote controls

    If you acquire one of the Pioneer HeNe laser-based LD players that uses a remote control (IR/wired for the VP-1000, IR for the others), then it may need some "maintenance" having likely been very well used and sitting around for a couple decades. Note that the two remote models described here - the RU-1000 and the CU-1100 - use the same codes and will work with both the VP-1000 and LD-1100, and probably the PR-8210 and other consumer models (but possibly not the industrial LD-V1000). I would guess that some people even prefer the RU-1000 due to its larger buttons for Still/Step, Slow, Fast 3X, and Scan. etc.


    This was Pioneer's first remote and may be used either with a wire connected by a wire (1/8" mono phone plugs at both ends) or IR using a proprietary code. This remote duplicates almost all the top panel buttons except for Eject and Slow Speed Adjust.

    Typical problems are one or more pushbutton switches that no longer click or work reliably.

    It's easy enough to gain access to the interior - pry off the two rubber feet at the top and remove the the 2 screws. The top then flips down and off. But the PCB is mounted to the front with a large number of plastic posts whose tops have been melted and squashed. :) If a button clicks but there is no response (the red LED doesn't light), then first try squirting some contact cleaner into the switch and exercising it. This will probably be all that's needed. However, if there isn't even a click, the switch will probably need to be replaced. This will require cutting the plastic posts on top or shaving them down so that the PCB can be *gently* lifted enough to enable the switch to be freed (after unsoldering its leads). The switches are common types and still readily available. Or, just swap one from a function that isn't used. :) Once any switches have been replaced, use hot-melt glue to secure the PCB around the edges. Some hot-melt on what's left of the plastic posts may help there but wedging something behind the PCB to provide support may be required.


    This is an IR-only remote that is much easier to repair than the RU-1000 since everything is held together with screws. Even if your remote is behaving, I recommend disassembling it to remove the likely rotted or about to rot foam cushion between the cover and the pushbutton switches. To remove the cover, take out the single screw in the battery compartment. Then, slide the top about 2 mm down to disengage the clips holding the thing together. The top can then be swung up (while still attached to the battery wires). Remove 6 screws holding the PCB in place and lift this up. Using a cotton swab or thin stick, lift up and discard all the foam and foam bits that are present. Clean any residue with isopropyl alcohol (rubbing alcohol is fine). Also clean the pushbutton switch buttons and PCB of any foam residue. Install the batteries (while the unit is still apart) and check for reliable operation of all buttons. Spray contact cleaner inside if needed. Where a button has lost its click or doesn't respond to contact cleaner, replacement will be required. They are readily available. Or, just swap one from a function you don't care about.

    Pioneer Laserdisc RS-232 commands

    (From: Jim Jackson (

    Here is a list of commands I have for controlling Pioneer players via the RS-232C jack. Hope it helps. I have also heard that there is supposedly a MCI driver for Windows but I haven't personally seen it. I tried these codes on a Pioneer machine I have at work using the Windows terminal program and was able to control the player. This file is from a public domain file for the amiga. I think I also have a C program (also for the amiga) somewhere if you need it.

    Communication protocol:

      COMMANDS       CHARS    HEX     DECIMAL              COMMENT
      Door Open       OP                                  open the door
      Reject          RJ                                  stop disc rotation
      Start           SA                                  start disc rotation
      Play            PL                                  (address)PL
      Pause           PA
      Still           ST                                  still frame
      Step Forward    SF
      Step Reverse    SR
      Scan Forward    NF
      Scan Reverse    NR
      MultiSpeed FWD  MF                                  (address)MF
      MultiSpeed REV  MR                                  (address)MR
      Speed           SP                                  integer SP
      Search          SE                                  address SE
      Stop Marker     SM                                  address SM
      Frame           FR                                  set frame mode
      Time            TM                                  set time code mode
      Chapter         CH                                  set chapter mode
      Audio Control   AD                                  integer AD 
      Video Control   VD                                  integer VD  0=off,1=on
      Display Control DS                                  integer DS  0=off,1=on
      Clear           CL                                  clear entry or mode
      Frame #         ?F                                  get frame number
      Time code #     ?T                                  get time code number
      Chapter #       ?C                                  get chapter number
      Player active?  ?P                                  P00=door
      Disc status     ?D                                  5 bytes and CR returned
      (and a few others....)
        Computer     Player
       ----------   --------
         TxD 2       3 RxD
         RxD 3       2 TxD
         CTS 5       4 DTR
         GND 7       1 GND
    For more info on your type of Pioneer player:
        Pioneer Communications of America, Inc.
        Engineering and Technical Support Deptment
        Sherbrooke Office Center
        600 East Crescent Avenue
        Upper Saddle River, NJ 07458-1827

    Pioneer '90' series LaserDisc player doesn't play older LDs

    "Check those discs you are playing. My 1090 won't play some older Image Discs including my (BOO HOO!) Bride Of Re-Animator disc."

    (From: Steven B (

    The 90 series of laser player had a fault that was fixed by Pioneer at no cost. It also caused a whole new series designation. Call Pioneer!

    Pioneer CD/LD Player Model CLD-S104 with shorted power supply

    (From Mark Z. (

    Your Pioneer LD has a shorted protective device, a V1B24 or similar. Looks like a diode and is located near the main AC input to the board. Clip it out, replace the fuse, and normal operation will resume. You STILL NEED to replace it; it protects some very expensive chips. Get the reference number off the board and call Pioneer at 800-457-2881.

    Pioneer 503 LD player sled slews to one end after service


    I have seen that before. The Sled runs on a differential op-amp. This uses +15V and -15V. One of these supplies is out. There are two fuses in power supply for this. Most likely u blew one when changing spindle motor. This will throw loading motor and sled motor, and maybe even the tilt motor (if it isn't also the loading motor) into overdrive in 1 direction. Loss of either supply will shift the differential one way.

    Pioneer CLD-D701 tray locking problem?

    "I've owned a Pioneer 701 laserdisc player for many years. Other than its tendency to drift out of alignment slowly and steadily over the years, it has been a good LD player. However, within the last year the tray has developed a strange problem. Each time I turn the 701 on and press the eject button to load a LD it takes about 6 seconds of gear grinding before the tray finally decides to come out. Just a couple of years ago the response was almost immediate.

    Once the tray has finally opened, thereafter it behaves normally and responds immediately for as long as the player is left on. Even if it's turned off briefly and back on, the tray behaves OK. However, if I wait to the next day the tray goes back to its nearly 6 second wait again.

    There appear to be several opinions as to the cause

    First suggests it is a sticky rubber problem:

    (From: Jeff Boettler (

    Eject the LD drawer and disconnect from the mains. Then remove the cover. On the 2950 there is a mechanism that clamps the disc that is suspended by metal bars running over the top of the drawer. Remove this, around four screws and locate the motor. There will be a rubber mat that grabs the disc. Clean this with meths and nothing else. Allow to dry and reassemble.

    Apparently this problem is accelerated by dirty labels on the LD and BBFC logos that have been removed, which leave a nasty deposit that rubs off on the mat.

    (From: Bruce Esquibel (

    I somewhat have a clue - but haven't came up with a 100% fix yet.

    The trouble appears to be the upper 'track' that hub/laser assembly uses when it returns from the side 2 position.

    This track floats within the metal sleeve on the upper left hand side as you look at the player from the rear (front away from you). It appears the last inch or so is warped or slightly deformed, probably because of age.

    If you examine the construction the track is pulled upward via a pair of springs and held in by a couple L-tabs or ears from the track. When the laser is returning from side 2 to stop you can see the track slightly move as the motor on the hub assembly runs on it.

    When it just about hits the end, that is when the grinding noise is heard, the gear on the shaft of the motor is spinning, but not meshing with that part of the track. It appears that after so much time the player detects the error and starts 'slapping' the hub around and eventually it grabs and does its flip.

    Odd part about this is that even the slightest pressure on either the track or hub will allow it to cycle without missing a beat.

    What I did, which reduced the grinding, but did not fix the trouble completely was to modify the rear spring to be tighter by carefully cutting the loop off and unwinding one turn, making into another loop. I suppose you can find another similar spring which has less turns also. The other bit that helped was kind of cheesy, the rear L-tab from the track seemed to have too much play when the motor ran near it. All I did was stick a small piece of electrical tape under it, on the metal housing which also tightened the track.

    I'm pretty sure the track itself is the problem, but it looks like a son-of-a-bitch to replace, even if it is a replaceable part. Another possibility is the gear on the motor shaft getting worn down but being the problem is only at that one end, I really don't think so.

    If you aren't into repair (just a joe consumer), I really don't recommend trying either the spring mod or tape bit, the spring can be easily malformed or the L-tab can break off, which either happening will put you in a world of hurt.

    All I can add is don't bother greasing the track, was the first thing I tried and it didn't help a bit. Also there was no indication of it needing lubrication anyway. This is a tolerance issue between the gear and track.

    The grinding noise, although sounding nasty, isn't really. It's not chewing up anything and I didn't even notice nylon dust around the area where the teeth are grinding. It's more of an annoyance problem than a major malfunction.

    Pioneer LD-3090 turn over problem

    (From: Kurtis Bahr (

    I once fixed a 3090 that had a problem when stopping the LD and the pickup tried to turn back over to side A. It actually made a grinding sound for awhile then finally grabbed into the turning assembly and turned over.

    The fix was to lubricate the metal guide shaft where it transfers from the playing shaft to the shaft on the turn mechanism. After this was done it has worked flawlessly.

    Sony LDP-1000A HeNe laser-based LaserDisc player

    The LDP-1000A was one of the few or possibly only Sony LDP that used a red (632.8 nm) HeNe laser. The LDP-1450 (below) was already laser diode-based. Use manuals for the LDP-1000A are readily available including free PDF downloads. I have not been able to find a service manual so am assuming that the descriptions below were for this machine.

    Sony KHS-100A Optical Pickup / Slider

    The KHS-100A is believed to be used in the LDP-1000A, though this is not much more than a wild guess based on a Web search turning up this single model as being HeNe-based. A complete KHS-100A is shown in Sony KHS-100A LD Player HeNe Laser-Based Optical Pickup / Slider Overall View. Note the DANGER labels because this is a real burning laser - NOT. ;-) It uses a Toshiba (!!) LG-3217 ~1 mW linearly polarized HeNe laser tube (same as one of the types used in the Pioneer HeNe laser-based LDPs). The optical design is similar to that of the Pioneer pickups (not the Phlips/Magnavox disaster), but appears to be lower cost. ;-) The main casting onto which everything is attached and the mount for the laser tube itself are metal which are partially molded with milled surfaces and pegs where precision is important. But all the optics mounts are plastic with minimal or no adjustments after gluing. So, the turning mirrors seat directly to the casting (compared to the Pioneer design where they are on screw-adjustable mounts). After removal of the covers over the laser and optics, here are all the gory details: Sony KHS-100A LD Player HeNe Laser-Based Optical Pickup / Slider with Parts Annotated. Following the laser, there is a mechanical shutter (!!), 1st 45 degree turning mirror, diffraction grating, beam expander, 2nd 45 degree turning mirror, Quarter WavePlate (QWP), and PBS cube. The output path gets reflected by the PBS cube to a single voice coil deflector at 45 degrees and to a 3rd 45 degree turning mirror to redirect the beam vertically to the objective lens. It is on a linear voice coil positioner for focus with the restoring force using only gravity. Thus, there is no chance of this LDP working at all unless it is flat on its back. ;-) The return path goes through a cylindrical lens at 45 degrees to the detector in a hermetic TO5 can with the ABCDEF photodiodes are on a single chip. The photodiode preamps are on a fully encapsulated hybrid module next to it.

    Note the single deflector. Most other similar LD players have a pair.

    There are V-grooves on two sides of the assembly indicating that it is indeed a slider and moves with respect to the LaserDisc rather than the other way around as with the Pioneer 7820.

    More to come.

    LDP-1000A HeNe laser power supply

    This is a linear power supply using the classic voltage doubler and set of 10 µF 450 V filter capacitors with a starter which appears to use a low voltage oscillator and mini-flyback transformer whose output winding is in series with the anode of the laser tube. The high voltage input is from the massive main power transformer for the LD player. Remarkably, after around 40 years, the electrolytic capacitors in the sample I tested were still healthy with low ESR and charged and maintained a charge normally. There are 3 low voltage connections to the supply but I have not yet determined what they do. Guessing low voltage DC power, GND/common, and enable. The linear regulator probably also requires a DC voltage, which would be one of these two.

    More to come.

    Sony LDP-1450 problems and discussion

    "I'm the proud owner of a very confused LDP-1450 from a Mad Dog McRee machine. It's got six option DIP switches, all are "off" (down), and>it's set for 1200 baud."

    (From: Ruben Panossian (

    The Extended Function dip switches are for just that, extended functions, which change certain characteristics of the player's operation. There are only three extended functions, using switches 1, 2, and 4 only. The other DIP switches are not used. Factory default is for all of the DIP switches to be set in the "off" position.

    The baud rate setting would not matter if you have nothing connected to the interface. BTW, it should be set for 9600 for ALG games.

    "Power-Up: Disc rotates 10-30 degrees in random directions, changing directions erratically every half-second or so, and the head makes a weird squeaking sound periodically as it tries to seek (maybe it's making physical contact with the disc??)"

    The objective is unable to find focus when this occurs. (usually) The disc will not spin-up to speed, rather, a slower turn and often in reverse. To determine if the player is finding focus you will need to get access to the lower PCB's. Turn the player on its *side* and remove the bottom cover. (Do *not* try to eject the disc in this position!) This is the servicing position.

    The large board you will see, behind the lower cover, is called MB-40. You will need to pull this board out a bit so you can work on it. Locate IC313, it is an HA11529. This IC controls the focus (coils), tracking (coils) and communicates to the main system control.

    Looking at the schematics, you can see that pin 36 of IC313 drives the focus coils. Pin 26 of IC313 is an output to the system control, which signals when focus is locked. By using a CRO, connect one channel to pin 26 and the other to pin 36. Adjust the display so that you can see the two signal but not on top of each other. You will need a CRO (or DSO, whatever) as the signals are about 3Vpp.

    Turn on the LD player (with a disc already loaded) and watch the signals. (the disc should be moving and sounds from the player) You should get a ramping (triangular) signal on pin 36 for a moment then a steady line (0V), indicating that focus has occurred. The signal on pin 26 (focus lock) is high, when focus is not locked, and low when locked. When the focus is locked the player should spin-up and go in to playback mode.

    Now, if you are finding that focus locks then searches then locks, in a peculiar way then you will have to do some more checking to determine the problem. This can be caused by many things.

    If focus is not locking and the signal on pin 36 is a constant triangular wave then the problem is more than likely in the optical block or the laser not turning on.

    Check to see if the objective is free. Next, check the continuity of the focus coils from the connector on the MB-40 board.

    You can check if the laser diode is turning on by checking the test point TP302 on the MB-40 board. It is located near IC312 which is a three pin -5V voltage regulator. When there is -5V on this test point the laser should be on. If there is no -5V there then check for -8 to -10V on R334 (any side) If there is no voltage there then there is a voltage rail supply problem. (like you hadn't guessed)

    If there is around -10V, then check the base on Q314. This is the right pin if the flat side is facing you, the right way around. It should have 0V on it to turn the laser on. Hmm... I will try again. One pin is connected to the +5V rail (collector), another pin, the emitter, drives the base of Q313 (which then supplies -10V to IC312) which should have +5V on it when the remaining pin (base) is at 0V. The base is connected to the LD "ON" or LD "OFF" signal. It is an active low signal, so a low signal will turn "on" transistor Q314 and in turn eventually turn on the laser diode. The laser diode also has an APC which complicates things, but don't worry about that at the moment.

    If the of base of Q314 is 0V and the collector is +5V then the emitter should have almost +5V on it. If not then the transistor must be real hot or dead. If it is hot, Q313 would be faulty. BTW, this transistor, Q314, is a pre-biased "digital" transistor. It is either fully on or off.

    I had a laser power problem like this, on a player out of a TT, which I had previously repaired. This time it turned out that the laser was not turning on all the time. Some times it would be ok for a couple of hours then it wouldn't work properly. By the time I had taken the covers off it was OK again. (Grrrr)

    To make a long and frustrating story short, I found that the laser wasn't being turned on when it should all the time. Turned out to be a bad connection on IC902, which is a 80 pin quad flat pack (SMD) and *only* pin 31 had a poor connection. This pin controls the laser diode "on" and "off" signal. I think I may have caused this poor connection when I was poking around previously.

    Also be careful when probing around a SMD like IC902. If you inadvertently short out a couple of pins, the slide motor may move (turbo) the optical block towards the spindle and not stop, causing a nice gear jumping noise that brings on a sudden panic attack. Which may cause you to knock over your LD player while trying to find the "OFF" button while still holding a cro probe. Although, I wouldn't admit to doing such a stupid thing, especially publicly. :-)

    Now, back to IC 313 on the M-40 PCB.

    If you are not getting a triangular wave or steady line on pin 36, but a wavy (sinus) signal then check the soldered joints on pins 38, 41 on IC313 and on R384, R382, R381, C337, C338. These are for phase compensation for the focus coil. If the signal looks strange on pin 36 of IC313 or the laser is turned on and IC313 is not working then IC313 or the serial control input signals may be your problem. I have only seen a couple of poor soldered connections on these, otherwise A+, players but you never know...

    If you find that focus is locking in say 10ms intervals (on and off) then the problem may be in the focus loop, which is initiated right when focus is locked. This loop controls the current supplied to the focus coil to maintain a constant current which is proportional to the focus error, so the focal point is maintained as the disc turns. Keep in mind that the focal length is not constant, as the disc is rotating.

    Or the problem could get interesting. In other words, *could* end-up being a "dog" of a problem, unless you have a manual. Either way a manual is essential. If you can read and understand the circuit diagrams then you shouldn't have any problems, other than the faults that were devised in hell.

    "Self Test: Removing the front cover revealed a "self test" jumper. Shorting the two pins together forced the player to spin up. The player correctly displays video for a few seconds (overlaid on the video is a frame number of approximately 7000), but quality, which starts off great, deteriorates rapidly, and the player then jumps back 100 frames or so and repeats the cycle. The words "NTSC 12" appear underneath the frame number whenever the self test jumper is shorted.

    The frames played are identical for any given disc. Mad Dog McRee gave me 7000ish, and Star Rider gave me 6900ish.

    When the player is in this mode, pressing the eject button causes the video to mute and the player to spin down. When the disc has stopped rotating, a further press of the eject button will eject the disc correctly, and a further pressing will reload the player."

    Yes, this is normal. Even if the focus error is greater than it's cut-off point the player will spin-up and try to display video. How good the video is will depend on how great the focus error is, I guess. I have done this myself, however, have found the video to be very jumpy and poor if any at all. When the focus error gets to it's cut-off point it re-initiates focus search..

    If the video is clear and stable then your problem sounds like it is not with the optical block, focus, etc. (with the test jumper closed)

    The test jumper you found is *only* meant for adjusting the "inner" and "outer" frame limits for the disc sizes, hence the displayed frame numbers.


    1. The player works but is still configured for a video game; it has to have something useful coming in on the RS-232 port in order for it to work."

    No. There were different LDP1450 software revisions though.

    With the Extended Function Dip switches all set to the "off" position the player will "spin-up" a disc and go to playback mode, when a disc is loaded.

    "2. This might be changeable (or I might get a different set of diagnostic information) if I knew what to do with the six option DIP switches."

    Yes and no. This is not your problem, though,.

    "3. The player is malfunctioning, probably something to do with alignment of the slide on which the optical head moves, and this accounts for the weird looping behavior I get in the self-test mode."

    Possible and no.


    1. Am I doing something boneheaded?

    No, considering the lack of information you have for this player. You could have done poking around IC902. I don't think that you will get very far without a service manual. The Sony service manual is relatively expensive, however, it is essential, It is also well detailed and clear, unlike some early player manuals.

    "2. Anyone know where I can get a service manual?"

    Yes, from Sony :-). Because it is not a real old LD player, they will have the manual.

    "3. I have yet to hook it up to a computer. I have a utility that purports to be able to talk to an LD player; would this help, or should I concentrate on getting it to work correctly in stand-alone mode before trying to talk to it?"

    This wouldn't help you with repairing the player, rather the opposite.

    Also, I forgot to mention one of the first things you should check for. Check the power supply voltages. Obviously +5V is ok. You should have an idea of which voltages are ok by what is working in the player as a start, anyway. There are around 10 voltage supplies or more including at least 5 different voltage rails.


    If anyone goes blind, destroys their LD player, decapitates their dog Fluffy, etc, by following my suggestions , it is not my fault. Only work on a LD player if you have an idea of what you are doing and understand what the dangers are. i.e., take blame for your own actions.

    Replacing a laserdisc player spindle motor

    With a CD player, all you have to get correct is the spindle height.

    Unfortunately, for a typical LD player, this is just the beginning.

    (From: Jack (

    Replacing a spindle motor is a "can of worms". I used to build these things!! You have a VERY critical height that is adjustable by three pylons with screws, etc. You need a special disc which had a "constant pitch" from inside to outside. There is also a method of doing this using a mirror disc (as the CD folks know about). You absolutely must have the LD player service manual!

  • Back to Optical Drive Repair FAQ Table of Contents.

    MinDisc Equipment

    MiniDisc record/write problems

    (From: David Vlack (

    To write a MD, a magnetic head is brought in contact with the top of the disk with the writing laser below. Without the magnetic head in place, no recording takes place. I have seen a few of these (mostly SHARP) where the actuator motor binds up. Taking it apart and freeing it up usually fixes the problem.

    Sony MiniDisk player/recorder considerations

    The Sony MiniDisk system was supposed to replace cassette tape as the preferred medium for portable music (and data). Yeh, well, I am not holding my breath but it may yet come to pass. The disks are about 2-1/2 inches in diameter and enclosed in a protective case like a 1.44 MB diskette. Thus, dirty disks, at least, should not be much of a problem. A MiniDisk (MD) holds approximately 1/5th as much raw data as a full size CD. Compression techniques are used to achieve the same maximum time for audio - about 74 minutes - supposedly with negligible loss in audio quality. (I won't get into that argument either).

    For playback of prerecorded discs, the optics and servo systems are operating in modes which are very similar to those in CD players and thus suffer from most of the afflictions and remedies described elsewhere in this document. The digital decoding and error correction including an advanced form of the CIRC may be substantially more sophisticated for MD players and MD data drives (if you can imagine that being possible) but the circuitry involved should be very reliable.

    However, for playback of MiniDisks recorded on MO (magneto-optical) media, there can be many other problems as the optics/electronics are sensing the different polarization of reflected light from the N and S magnetized spots rather than pits and lands. The signal-to-noise ratio of the MO effect may be lower than that of a stamped disc. Thus, prerecorded media with the normal pits and lands on the information layer may work fine but MO media may suffer from tracking, audio noise, or uncorrectable data errors. Servo adjustments for tracking and CLV spindle control may be even more critical than for CD players.

    Note that some MDs may include both prerecorded (stamped) and MO sections so that it is possible that only certain portions of these disks will play reliably.

    MiniDisk recording requires that the laser diode be operated at higher power (around 4.5 mW optical output compared with less than 1 mW for reading) and that an electromagnetic head in contact with the back of the MD is driven with the EFM coded data pattern. This is not really a write head such as that used in a computer disk drive - the laser beam does the actual writing by heating the MO layer but the magnetic field determines the polarity (e.g., 1 or 0, N or S) of the written spots. Therefore, the actual position of the head is not critical - there is no servo for it! Note that this approach contrasts with that used in many other MO drives where the laser power is modulated to write 1s and 0s. The 'Magnetic Field Modulation' approach used with the MiniDisk claims many advantages in terms of robustness when confronted with less than perfect optical alignment and control of laser power, among others.

    CLV servo lock during recording is determined by a signal derived be impressing a reference modulation (wiggle) on the premastered groove wall position - yet another possible area for failure or need for servo adjustments!

    CAUTION: the higher power laser output required for recording is substantially more hazardous than that of CD players. However, since under normal conditions even with the case disassembled, the disk and electromagnet will be blocking the lens, there is little danger. However, if you remove the electromagnet and there is no disk in place, this optical power must be treated with respect.

    Sony MDS 302 Minidisc optical blocks

    This likely pertains to other Sony models as well.

    (From: Shawn (

    These is a very common problem with Sony MD/CD players. I'll bet it is skipping and/or ruining your recordable MD's, right? It causes far more "disasters" with MD because an MD deck that has trouble reading a recordable MD will think it is corrupt and try to write a new TOC, which can ruin the contents of the disc! When this occurs, press the STOP button until the "TOC" indicator disappears (may take up to 10 seconds) and eject your disc, it will come out unharmed.

    Anyhow, on to the optical block problems. I will bet your MDS302 will work fine if turned on its side or upside-down. I have seen this problem many times with Sony MD/CD equipment. I have MD players from Sharp which are much older and have suffered great abuses (like being run over by a car) which don't suffer this problem.

    My only guess is that it's either a problem with the lens suspension or the focusing coil. It is definitely a problem with the focusing system in the optical block because: A) replacing the block fixes the problem B) sometimes adjusting Focus Bias on the deck will compensate and reduce or eliminate the problem. C) I have fooled around under the cover of the optical block and have experimented using pieces of tape to suspend the lens suspension. I suspect this compensates for either a poorly functioning suspension or a screwy focus coil. I have been able to regain 100% perfect operation using this fudge-fix method!

    Unfortunately, to fix this problem properly, you will need the new optical block. We can only hope that Sony will correct this problem! BTW, you could always use your deck upside-down or sideways. :(

  • Back to Optical Drive Repair FAQ Table of Contents.

    DVD Equipment

    CD and DVD support on same drive

    Digital Versatile (or Video) Disc players should be hitting the streets by now or at least very soon. What this means is that DVD players will need repair just like CD players.

    While much of the basic construction of CD and DVD players is similar, in order for a single player to work with both CDs and DVDs requires some fancy footwork to avoid the costs of dual laser pickups. This comes about from the change in the laser wavelength (780 nm for CDs, 632 nm for DVDs) and thickness of the disc (1.2 mm for CDs, .6 mm for DVDs). This requires differences in the optics to produce the proper spot size and readback image on the photodiode array.

    (From: Bill Studenmund (

    I saw an overview in a journal on what they're doing, and it's pretty cool. They have a variable aperture in the beam (maybe it's on a hinge and snaps into the beam path?). In one setting, the beam is the right diameter to fill an inner area of the objective, and focuses to a spot the right diameter for reading normal CD's. The spot has correction for the spherical aberration from 1.2 mm of disk.

    When the aperture is not in the beam, it fills the full aperture of the lens. There's a holographic grating on the lens so the the combination of the inner and outer areas is diffraction limited for 635 and compensates for 0.6 mm of disk.

    Though the signal to noise ratio will be lower as the 1/4 wavelength's a bit off, I doubt it'll be a problem. The electronics have gotten so good that they can read a disk w/o metal backing! That's how the Sony dual-layer disk technique works. There are two surfaces with data, and the one in the disk has no aluminum backing. They get enough S/N to read that layer. It's about 50 um above the "normal" layer, so not much of a defocus.

    Could DVD discs be made with compatible CD tracks?

    CDs are 1.2 mm thick. DVDs consist of two bonded .6 mm substrates. In principle, the DVD layer could be made partially transparent permitting a CD player's laser beam to focus through it to some tracks of CD information pressed in their normal position 1.2 mm from the bottom surface.

    As a practical matter, it is very unlikely that any existing CD player could be made to work with such a scheme. It would be like viewing the pits through a frosted plastic screen - theoretically possible but substantially reducing the signal to noise ratio. Furthermore, the CD focus servo would very likely lock onto the DVD rather than the CD layer as it goes through its focus search routine.

    It might be possible to design such a CD player but why would anyone want one? By the time this matters, DVD players will either be mainstream (CD-only players may not even be available any more) or will have been superseded by something even more wonderful. Why would you pay a premium for a DVD pressing and then only want to play portions of it on a CD player anyhow?

  • Back to Optical Drive Repair FAQ Table of Contents.

    WORM Drives

    WORM drive Laser Diodes

    (From: Alan Shinn (

    Well, I bought a few of those WORM drives I wrote about. The LD puts out at 30mW at 110mA, As measured by using it to heat up a surface mount transistor hooked up as a thermometer with a surface mount resistor glued onto it for calibration.. I wish I had gotten more. Not that I know what I will do with them (the LDs) The drives also have several rare earth magnets so they were quite a fun deal.

  • Back to Optical Drive Repair FAQ Table of Contents.

    CD-R Equipment

    Differences between CD and CD-R media

    (From: Michael Portmann (

    I have a flyer on Mitsui CD-R media. I quote from this:

    The difference between a CD-R and a CD-ROM lies in the structural layers between the polycarbonate substrate and the protective lacquer surface that both discs possess.

    The CD-R has one long groove stamped in the polycarbonate substrate to guide the laser. This groove is covered with an organic dye layer, which, when written upon by the heat of a higher powered laser light from the recorder, will deform to produce the 'pits' and 'lands' of information. The dye is protected by a non-corrosive, highly reflective thin layer of gold. One the CD-R layer is recorded, the deformations in the dye become permanent.

    The Mitsui gold CD uses a patented Phthalocyanine Dye & Data shield surface.

    They then go on to mention how unlike Cyanine based CD-R, theirs shows less degeneration from continuous exposure to light and heat.

    HP 4020i/Philips CDD2000 Spring Fix for Write Append Errors

    (From: Rick Richardson (

    Here is the fix I applied to my two year old HP 4020i CD-R recorder when I started to get Write Append errors when writing CD's larger than about 550 MBs.

    I got a tip that this problem was due to a "spring" wearing out or of insufficient strength from David Neal on the mailing list (Unix CD-R software mailing list).

    Armed with this clue, I searched DejaNews on the subject of CDD2000 & Spring. Here I found basically two theories for the problem - the spring theory and another one that said it is dust on the laser lens that needs to be blown off with compressed air (*not* wiped).

    Since my HP 4020i drive is over two years old, I figured I had nothing to lose by opening it up and seeing if I couldn't apply the "spring fix". Also, at the same time I blew off the laser lens with compressed air.

    After applying the "spring fix" and blowing the lens with air, the drive now works 100% again. I cannot say with confidence which of the these actually fixed the drive.

    I attach the approximate procedure I used for applying the "spring fix" below. I disclaim any responsibility for the correctness or incorrectness of this fix. Apply the fix will void your warranty. You should not attempt the fix unless you have the proper tools and ability.

    Tools Needed:

    Parts Needed: Skills Needed: The first step is to remove the case. Remove two screws with the T-10 screwdriver and four screws with the T-? screwdriver. Remove metal case. Gently release the top circuit board from two plastic alignment posts -- this may require gradual rocking of the circuit board but do not stress the circuit board as it is very thin.

    The next step is to remove the main circuit board by disconnecting three ribbon cables and two sets of two pin connectors. The larger ribbon cables are released by moving two pieces of plastic at each end of the cable connector away from the connector body by about 1/8". The cables should then easily slide out of the connector. The smaller cable has a slightly different release mechanism, but again just move it about 1/8" away from the connector body. Slowly rock the two pin cables from their sockets.

    You should now be able to see 4 more T-10 screws. Remove these to free the drive mechanism from the other part of the metal case.

    The next step is to remove the smaller circuit board on the laser transport assembly. Remove 4 philips head screws. Pull the board up and lay it over - you will not be able to fully remove the board because two wires are soldered to the motor.

    If you look at the transport now, you will see a worm gear which drives a regular gear which drives a rack gear. The rack gear is spring loaded to press up against the regular gear. According to theory, the spring which causes this pressure is worn out and/or not designed to be strong enough.

    The spring itself is a straight length of springy wire, about 1" in length and rumored to be about .012" in diameter. Since I don't own calipers, I couldn't verify this.

    The spring is held in place only by its springiness. Each end fits into a slot and the middle is bowed down an under a notch in the plastic rack gear.

    What you want to do is add a *second* spring wire. You should not need to remove the original spring wire. I found a suitable wire in a 5.25" floppy drive I had laying around. I removed the wire from the floppy drive and straightened out a couple of bends that were in it and ended up with a straight piece of springy wire about 1.25" long, which is longer than the spring in the CD-R drive. You want it longer for now because it is easier to install it that way. It will be cut to length later. Use the two pairs of needle nose pliers to straighten the spring wire.

    With your finger, rotate the worm gear on the shaft of the motor to move the transport carriage so that the center of the spring is under the center of the regular gear. You should be able to see the notches that hold both end of the spring now.

    Lay your new spring on top of these notches. Using the blade of a small screwdriver perpendicular to the length of the spring, press the spring down in the middle until it is underneath the slot in the black rack gear. This bows the spring about 1/8" in the middle. The spring should now be in place.

    Using your smallest dikes, cut the ends of the spring wire off so that they are the proper length. Wear eye protection when doing this, and if possible grasp the end being cut off with needle nose pliers so that the wire won't fly around the room or worse into the drive mechanism.

    With the drive still opened up, use a can of compressed air to blow off the dust on the laser lens. DO NOT touch the laser lens as it is magnetically floating in its holder.

    Now, reassemble the drive by reversing the disassembly instructions.

  • Back to Optical Drive Repair FAQ Table of Contents.

    -- end V1.57 --