Atari Vector Monitor Repair/Upgrade


  14.1) Input Protection Circuit (IPC) PCB Parts List

Part No.   Description (Reference Designations in parentheses)
========== ===========================================================
24-250107  100 uf Aluminum Elec. Fixed Axial-Lead 25V Capacitor (C1,2)
31-1N914   75V Type-1N914 Switching Diode (CR2-4)
32-1N751A  5.1V 400mW Type-1N751A Zener Diode (CR1)
33-2N3906  PCB Switching and Amplifying Transistor (Q2, 4, 5)
34-2N3904  Type-2N3904 NPN 60V 1-Watt Transistor (Q1, 3)
52-222     22-Gauge Jumper Wire (2 in. required)
110000-223 22K Ohm, +/- 5% 1/4 W Resistor (R1, 8, 11)
110000-273 27K Ohm, +/- 5% 1/4 W Resistor (R5)
110000-393 39K Ohm, +/- 5% 1/4 W Resistor (R4)
110000-682 6.8K Ohm, +/- 5% 1/4 W Resistor (R6, 7)
110001-222 2.2K Ohm, +/- 5% 1/2 W Resistor (R10)
110001-472 4.7K Ohm, +/- 5% 1/2 W Resistor (R9)
110011-122 1.2K Ohm, +/- 1% 1/4 W Metal-Film Resistor (R2, 3)
[110000-102 1K Ohm, +/- 5% 1/4 W Resistor (R')]

A038088-01 B

[Figure 1, a scale picture of the top side of the PCB listing numbered connection points onto the deflection board, has been omitted for obvious reasons]

  14.2) Schematic for IPC

[R' added by me as documented in TM-268]

     Y INPUT             +27V              X INPUT
        :                  :                  :
        :                  *J6                :
        :                  |                  :
        :                  \                  :
        :             CR1  / R1               :
        :           1N751A \ 22K              :
        :            5.1V  /                  :
        :             \    |                  :
        :         +--->|---+                  :
        :         |   \    |                  :
        :   R3   ===       |             R2   :
        :  1.2K   =        |            1.2K  :
        :   1%             |             1%   :
        |       J4:   CR3     CR2   :J2       |
        |         :  1N914   1N914  :         |
        /         :                 :         \
    R5  \  To R601 1.6K 2%    To R701 1.3K 2% /  R4
    27K /                                     \ 39K
        \   + C2 -                   - C1 +   /
        |   100 uf                   100 uf   |
        |    25 V          J5         25 V    |
        |            |     |     |            |
        |            |    ===    |            |
        |     R7     |     =     |     R6     |
        +----/\/\----+           +----/\/\----+
        |    6.8K        +27V         6.8K    |
        |                  :                  |
        |                  *J6                |
        |                  |                  |
        |                  \                  |
    Q4  +-----+  Q3     R' /        Q1  +-----+  Q2
  2N3906|  b  |2N3904   1K \      2N3904|  b  |2N3906
       ---   ---       1/4W/           ---   ---
     c / \ e / \ c         |         c / \ e / \ c
      |   | |   +----------+----------+   | |   |
      |   | |                             | |   |
      |   | +--------------+--------------+ |   |
      |   |                |                |   |
      |  ===              \ / CR4          ===  |
      |   =               --- 1N914         =   |
      |                    |                    |
      |                Q5  |
      |              2N3906| b
      |                   ---
      |                 c / \ e
      |                  |   +------------------+
      |        +---------+---------+            |
      |        |         |         |            |
      \        \         \         \            |
      / R8     / R11     / R10     / R9         |
      \ 22K    \ 22K     \ 2.2K    \ 4.7K       |
      /        /         / 1/2W    / 1/2W       |
      |        |         |         |            |
    J7*--------+       J9*         *J8          *J5
      :                  :         :           ===
    -27V             To D700   To D600          =



  1. Remove R600, R605, R700 and R706.

  2. Remove solder from all nine holes indicated in figure 13 [figure not included; see text below].
  3. Straighten pins of PCB so that they are perpendicular to the board [meaningless to you since you probably don't have the board].
  4. Match and insert the numbered holes in figure 13 with the numbered pins in figure 1 [see text below].
  5. Solder.

[Figure 13, an annotated picture of the deflection board PCB from the original TM-183 manual, has been omitted for obvious reasons.]

[Since you will be making the board from scratch and don't have the pictures that came with the board, I am providing the following text to describe the contact points on the deflection board. The following text is all mine and NOT Atari's but is derived directly from figures 1 and 13 that Atari did provide.]

All descriptions refer to a deflection board oriented component side up with the board label "P314" at the top (right-side-up) and the 2 large electrolytic capacitors at the bottom. This orientation will have the electrolytics "side by side" and the board will be "taller" than it is "wide".

SPECIAL NOTE: According to the Major Havoc manual, this board came in 2 versions. Later versions had a 1K Ohm, +/-5%, 1/4 W resistor as one of the "stilts" on the board instead of a plain piece of wire. If your board does not have this resistor, here is what you need to do.

  1. Locate the "stilt" wire connected to resistor R1 (22K ohm) and the collectors of transistors Q1 and Q3 (type 2N3904) on the Input Protection Circuit PCB (the other end is connected to the P314 Deflection PCB).
  2. Use a wire cutter to cut the wire, located in step 1, half-way between the two PCBs.
  3. Use a soldering iron to solder a 1K Ohm, +/-5%, 1/4 W resistor between the two ends of the wire cut in step 2.

I have included this resistor in my ASCII rendering of the schematic and labeled it R'.

Chapter 15) How to make a 'TEMPEST' Monitor Trouble-Free.

Here is an article from the April 15, 1983 issue of Play Meter magazine (page 191) which is copyrighted material and is included without permission; forgive me. It is from a regular feature in the magazine called "FRANK'S CRANKS" by Frank "The Crank" Seninsky.


[NOTE: Play Meter did copyright this article and the magazine is clearly marked with a copyright symbol.]


Atari's Tempest, when it is working, is not a bad game. It's just a shame that the monitors only last a few weeks (sometimes only days) between service calls. Most of the time, the monitor sits neglected on a techroom shelf.

Atari has developed a monitor protection board [included earlier in this text] to protect the monitor's components (2N3716 and 2N3792 "X" OUTput transistors, two each located on chassis frame) if and when there is a RAM lock-up on the Tempest CPU board. I want to clarify that the Wells-Gardner monitor is not at fault. Also note that on the later Atari games, the protection circuit has been incorporated into the board circuitry. [These statements seem to imply that this "fix" is compatible with the Atari upgraded P314s as well as P327s and P339s and will provide additional protection; if fact, I have seen it on a P327 before. It is sufficiently ambiguous that the exact opposite can be inferred. Judging from the areas of the board it alters, I would say it is incompatible (duplicates) the other fixes in this section.]

It's common knowledge that you can purchase a broken Tempest game cheap. With about 20 minutes of your time and a couple of dollars in parts, it is possible to add just six common components to the monitor deflection board and have a Tempest that will stay on location and work [Yeah, right]!

The parts required are:

  15.1) FIRST HALF

Take the anode ends (the ends opposite from the marked rings) of a 1N914 and a 1N4737, and solder them to one end of a 1K ohm resistor so that it looks like this:

                               ANODE +------+-+ CATHODE
                            +--------+1N4737| +--------+ GROUND
CATHODE +-+------+ ANODE   /         +------+-+        |
--------+ | 1N914+--------+                           ===  C700
R700    +-+------+         \         +--------+        |
                            +--------+ 1K ohm +--------+ -27 VOLTS

Locate C700 in the top left of the monitor deflection board. (See Figure 13 on page 20 of Atari TM-183 Wells-Gardner Quadrascan service manual; second printing) and solder the cathode of the 1N4737 to the ground side of C700 (right side in Figure 13). Solder the end of the 1K OHM resistor to the -27 volt side (left side) of C700. Solder the one remaining wire (the cathode of 1N914) to the "X" INput side of R700 (top end of R700). You are now halfway finished.

  15.2) HALF TIME

Take a five-minute break; you deserve it.


Take the remaining 1N914 and 1N7437, and solder the cathode ends of each diode together with one end of the 1K OHM resistor so it looks like this:

             ANODE +------+-+ CATHODE
GROUND    +--------+1N4737| +--------+
          |        +------+-+         \ CATHODE +-+------+   ANODE
C701     ===                           +--------+ | 1N914+--------
          |        +--------+         /         +-+------+    R700
+27 VOLTS +--------+ 1K ohm +--------+

Locate C701 (top middle in Figure 13) and solder the anode of 1N4737 to the ground side of C701 (right side). Solder the end of the 1K OHM resistor to the +27 volt side of C701 (left side). Go back to the same "X" INput side of R700 and solder the remaining wire (the anode of the 1N914) to this connection. Make sure that you have a good solder connection at the "X" INput of R700 as you now have a three-wire joint.


Make sure that none of the wires of this modification can come into contact with the other board components [easy to do; there is lots of bare PCB in this area; you may want to tape/glue the leads down], especially the brown ground wire located to the right of R700. If the modification hits this brown wire, you can consider it a fumble and you just blew your lead and the game.


Chapter 16) Deflection board "hacks" to extend life

Lastly, I will list 2 hacks that I have seen made to deflection boards in an attempt to get them to work for longer periods in the field. I have seen them on both the P314 and P327 designs. The first one makes some sense but the second one is downright scary!

  16.1) Hack 1

Cut the trace just above pin 4 of connector P101 isolating the 3 topmost connections (purple wire, R713, and pin 7 of P700) from the rest of the cluster. Jumper the 3 isolated connections to pin 7 of P100. This makes those 3 connections run at -33.3V instead of the usual -27.7V.

Cut the trace just to the left of pin 3 of P101 isolating the 5 rightmost connections (F700, R808, pin 5 of P701, C104, and R712) from the rest of the cluster. Jumper the 5 isolated connections to pin 1 of P100. This makes those 5 connections run at 33.8V instead of the usual 27.8V.

I am not sure what is gained by biasing these portions of the circuit by larger magnitude voltages but will look into it later.

  16.2) Hack 2

When I saw this next hack, I couldn't believe my eyes; especially after I plugged it in and IT WORKED! The hack described above was implemented but with the following additions...

Evidently this operator got so tired of fixing the low voltage power supply regulator circuitry that he ELIMINATED IT FROM THE CIRCUIT! What he did was remove virtually that entire section (R100-103, D104-105, and P100) and instead formed the voltages required by dropping the unregulated +/-33 voltages across resistors! He connected a 10 Watt, 25 Ohm (+/- 10%) resistor between pins 3 and 7 of P100. An identical resistor was connected between pins 1 and 4 of P100. I'm not sure what kind of solder he used but it is takes a good minute for a 30 Watt soldering iron to even begin to melt a small portion of it.

This change will give you a very noisy approximation of the original voltages that should be good enough to run the monitor. Needless to say, the ceramic resistors get unbelievably hot and the screen is a little jumpy when drastic changes in drawing (current pull) occur (such as between waves and during the demo) but other than that the results are quite tolerable. If run for extended periods, this setup is virtually guaranteed to blow some fuses on the deflection board.

Since there is no longer a Q101 to worry about, it won't cause you any problems and since P100 no longer exists (either it or the connector that goes to it should be removed to avoid somebody plugging it in and adding the transistors to the now foreign circuit), there won't be any problems with Q102 and Q103 either (they are no longer required in the circuit and the connector that went on the now missing P100 just hangs in the air). If you are going to be placing one of these monitors out in the field or it is going to get frequent, extended duration use, this hack MIGHT be worth trying (assuming the degradation of picture quality is acceptable to the viewers) but I would think it would greatly stress the rest of the circuitry as well as the yoke coils and would limit the lifetime of the unit in other, less familiar ways. The PCB I saw this on had extensive burns on the amplification portions of the circuit which I almost never have to repair so BEWARE; this hack may have been the cause not the solution!

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