Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools


  10.19) Soldering tabs onto NiCd batteries

When replacing NiCd batteries in packs or portable tools, it is often
necessary to attach wires to the individual cells.  It may be possible to
obtain NiCds with solder tabs attached (Radio Shack has these) but if
yours do not, here are two ways that work.  They both require a (Weller)
high wattage soldering gun.

I use a high power Weller (140 W) soldering gun.  Use fine sandpaper to
thoroughly clean and roughen up the surface of the battery cell at both
ends.  Tin the wires ahead of time as well.  Arrange the wire and cell
so that they are in their final position - use a vise or clamp or buddy
to do this.  Heat up the soldering gun but do not touch it to the battery
until it is hot - perhaps 10 seconds.  Then, heat the contact area on the
battery end while applying solder.  It should melt and flow quite quickly.
As soon as the solder adheres to the battery, remove the heat without
moving anything for a few seconds.  Inspect and test the joint.
A high power soldering iron can also be used.

Here is a novel approach that appears to work:

(From: Clifford Buttschardt (cbuttsch@slonet.org)).

There is really no great amount of danger spot welding tabs!  They usually
are made of pure nickel material.  I put two sharp pointed copper wires in
a soldering gun, place both on the tab in contact with the battery case
and pull the trigger for a short burst.  The battery remains cool.

(From: mcovingt@ai.uga.edu (Michael Covington)).

Of course!  A soldering gun is a source of about 1.5 V at 100 A RMS.
Should make a fine spot-welder.  You should write that up for QST
("Hints and Kinks") or better yet, send it in a letter to the editor
of "Electronics Now" (the magazine I write for).

  10.20) How do those on-battery or on-the-package battery testers work?

There is a graded width resistance element that gets connected when you pinch
those two points.  It heats up - substantially, BTW.  Some sort of liquid
crystal or other heat sensitive material changes from dark to clear or yellow
at a fairly well defined temperature.

Incidentally, since the current is significant, repeated 'testing' will drain
the batteries - as with any proper under-load battery test!  This isn't an
issue for occasional testing but if the kids figure how to do this....

Personally, I would rather use a $3 battery checker instead of paying for
throw-away frills!

  10.21) Battery eliminator for laptop or appliance with dead NiCd

Even where you have the AC adapter, it is quite likely that simply removing
the (shorted) battery pack will not allow you to use it.  This is because
it probably uses the battery as a smoothing capacitor.  You cannot simply
replace the battery with a large electrolytic capacitor because the battery
also limits the voltage to a value determined by the number of cells in the
pack.  Without it, the voltage would be much too high, possibly resulting in
damage.  You could use N power diodes in series (i.e., N=Vb/.7) to drop the
approximate voltage of the battery pack AND a large capacitor but you would be
wasting a lot of power in the form of heat.

One alternative is to substitute a regulated power supply with an output equal
to the the battery voltage and current capacity found by dividing the VA
rating of the normal wall adapter by the battery's nominal terminal voltage
(this will be worst case - actual requirements may be less).  Connect this
directly in place of the original battery pack.  Unless there is some other
sort of interlock, the equipment should be perfectly happy and think it is
operating from battery power!

Also see the chapter: "AC Adapters and Transformers".

Chapter 11) Incandescent Light Bulbs, Lamps, and Lighting Fixtures

Editor's note: More information on incandescent light bulbs can be found
at: http://www.misty.com/~don/.

  11.1) Incandescent light bulbs - single and three way

The basic incandescent lamp operates on the same basic principles as
the original carbon filament lamp developed by Thomas Edison.  However,
several fundamental changes have made it somewhat more efficient and
robust.  However, modern bulbs are hardly efficient at producing lighte.
Typically, only about 3 to 7 percent of the electrical energy used by a
typical incandescent light bulb is turned into useful (visible) light.  The
rest goes to waste (usually) as heat.

Tungsten replaced carbon as the filament material once techniques for
working this very brittle metal were perfected (Edison knew about tungsten
but had no way of forming it into fine wire).  Most light bulbs are now filled
with an inert gas rather than containing a vacuum like Edison's originals.
This serves two purposes: it reduces filament evaporation and thus prolongs
bulb life and reduces bulb blackening and it allows the filament to operate
at a higher temperature and thus improves color and brightness.  However,
the gas conducts heat away so some additional power is wasted to heating
the surroundings.

Incandescent lamps come in all sizes from a fraction of a watt type smaller
than a grain of wheat to a 75 KW monsters bulbs.  In the home, the most common
bulbs for lighting purposes are between 4 W night light bulbs and 250-300 W
torch bulbs (floor standing pole lamps directing light upwards).  For
general use, the 60, 75, and 100 W varieties are most common.  Recently,
55, 70 and 95 W 'energy saving' bulbs have been introduced.  However, these
are just a compromise between slightly reduced energy use and slightly less
light.  My recommendation: use compact fluorescents to save energy if these
fit your needs.  Otherwise, use standard light bulbs.

Most common bases are the Edison medium (the one we all know and love) and
the candelabra (the smaller style for night lights, chandeliers, and wall

Three-way bulbs include two filaments.  The three combinations of which
filaments are powered result in low, medium, and high output.  A typical
3-way bulb might be 50 (1), 100 (2), and 150 (1+2) W.  If either of the
filaments blows out, the other may still be used as a regular bulb.
Unfortunately, 3-way bulbs do tend to be much more expensive than ordinary
light bulbs.  There may be adapters to permit a pair of normal bulbs to
be used in a 3-way socket - assuming the space exists to do this safely
(without scorching the shade).

The base of a 3-way bulb has an additional ring to allow contact to the second
filament.  Inexpensive 3-way sockets (not to be confused with 3-way wall
switches for operation of a built-in fixture from two different locations)
allow any table lamp to use a 3-way bulb.

Flashlight bulbs are a special category which are generally very small
and run on low voltage (1.5-12 V).  They usually have a filament which is
fairly compact, rugged, and accurately positioned to permit the use of a
reflector or lens to focus the light into a fixed or variable width beam.
These usually use a miniature screw or flange type base although many
others are possible.  When replacing a flashlight bulb, you must match
the new bulb to the number and type of battery cells in your flashlight.

Automotive bulbs are another common category which come in a variety of
shapes and styles with one or two filaments.  Most now run on 12 V.

Other common types of incandescent bulbs: colored, tubular, decorative,
indoor and outdoor reflector, appliance, ruggedized, high voltage (130 V).

  11.2) Why do my light bulbs seem to burn out at warp speed?

The lifespan of an average incandescent bulb is 750-1000 hours which is
about 1.5 months if left on continuously or roughly 4 months if used 8 hours
a day.  So, if  you are seeing a 3-4 month lifespan, this may not be that out
of line depending on usage.  With a lot of bulbs in a house, you may just think
you are replacing bulbs quite often.

Having said that, several things can shorted lamp life:

1. Higher than normal voltage - the lifespan decreases drastically for slight
   increases in voltage (though momentary excursions to 125 V, say, should
   not be significant).

2. Vibration - what is the fixture mounted in, under, or on?

3. High temperatures - make sure you are not exceeding the maximum recommended.
   wattage for your fixture(s).

4. Bad switches bad connections due to voltage fluctuations.  If jiggling
   or tapping the switch causes the light to flicker, this is a definite
   possibility.  Repeated thermal shock may weaken and blow the filament.

A bad neutral connection at your electrical service entrance could result
in certain circuits in your house having a higher voltage than normal -
multimeter would quickly identify any.

It may be possible to get your power company to put a recording voltmeter
on your line to see if there are regular extended periods of higher than
normal voltage - above 120 to 125 V.

To confirm that the problem is real, label the light bulbs with their date
(and possibly place of purchase or batch number - bad light bulbs are also
a possibility).  An indelible marker should be satisfactory.

Of course, consider using compact or ordinary fluorescent lamps where
appropriate.  Use higher voltage (130 V) bulbs in hard to reach places.
Bulbs with reinforced filament supports ('tuff bulbs') are also available
where vibration is a problem.

  11.3) Halogen bulbs

(From: Don Klipstein (don@misty.com)).

A halogen bulb is an ordinary incandescent bulb, with a few modifications.
The fill gas includes traces of a halogen, often but not necessarily iodine.
The purpose of this halogen is to return evaporated tungsten to the filament.

As tungsten evaporates from the filament, it usually condenses on the inner
surface of the bulb. The halogen is chemically reactive, and combines with
this tungsten deposit on the glass to produce tungsten halides, which
evaporate fairly easily. When the tungsten halide reaches the filament, the
intense heat of the filament causes the halide to break down, releasing
tungsten back to the filament.

This process, known as the halogen cycle, extends the life of the filament
somewhat. Problems with uneven filament evaporation and uneven deposition of
tungsten onto the filament by the halogen cycle do occur, which limits the
ability of the halogen cycle to prolong the life of the bulb. However, the
halogen cycle keeps the inner surface of the bulb clean. This lets halogen
bulbs stay close to full brightness as they age.  (recall how blackened
an ordinary incandescent bulb can become near the end of its life --- sam).

In order for the halogen cycle to work, the bulb surface must be very hot,
generally over 250 degrees Celsius (482 degrees Fahrenheit). The halogen may
not adequately vaporize or fail to adequately react with condensed tungsten
if the bulb is too cool. This means that the bulb must be small and made
of either quartz or a high-strength, heat-resistant grade of glass known
as "hard glass".

Since the bulb is small and usually fairly strong, the bulb can be filled
with gas to a higher pressure than usual. This slows down the evaporation
of the filament. In addition, the small size of the bulb sometimes makes it
economical to use premium fill gases such as krypton and xenon instead of
the cheaper argon. The higher pressure and better fill gases can extend
the life of the bulb and/or permit a higher filament temperature that results
in higher efficiency. Any use of premium fill gases also results in less heat
being conducted from the filament by the fill gas, meaning more energy leaves
the filament by radiation, meaning a slight improvement in efficiency.

  11.4) Efficiency, lifetime, and failure modes of halogen bulbs

A halogen bulb is often 10 to 20 percent more efficient than an ordinary
incandescent bulb of similar voltage, wattage, and life expectancy. Halogen
bulbs may also have two to three times as long a lifetime as ordinary bulbs,
sometimes also with an improvement in efficiency of up to 10 percent. How much
the lifetime and efficiency are improved depends largely on whether a premium
fill gas (usually krypton, sometimes xenon) or argon is used.

Halogen bulbs usually fail the same way that ordinary incandescent bulbs
do, usually from melting or breakage of a thin spot in an aging filament.

Thin spots can develop in the filaments of halogen bulbs, since the 
filaments can evaporate unevenly and the halogen cycle does redeposit 
evaporated tungsten in a perfect, even manner nor always in the parts of 
the filament that have evaporated the most.  However, there are additional
failure modes which result in similar kinds of filament degradation.

It is generally not a good idea to touch halogen bulbs, especially the more
compact, hotter-running quartz ones. Organic matter and salts are not good
for hot quartz. Organic matter such as grease can carbonize, leaving a dark
spot that absorbs radiation from the filament and becomes excessively hot.
Salts and alkaline materials (such as ash) can sometimes "leach" into hot
quartz, which typically weakens the quartz, since alkali and alkaline 
earth metal ions are slightly mobile in hot glasses and hot quartz.
Contaminants may also cause hot quartz to crystallize, weakening it. Any of 
these mechanisms can cause the bulb to crack or even violently shatter.
For this reason, halogen bulbs should only be operated within a suitable
fully enclosed fixture.  If a quartz halogen bulb is touched, it should
be cleaned with alcohol to  remove any traces of grease. Traces of salt
will also be removed if the alcohol has some water in it.

  11.5) Use of dimmers with halogen bulbs

Dimming a halogen bulb, like dimming any other incandescent lamp, greatly
slows down the formation of thin spots in the filament due to uneven
filament evaporation. However, "necking" of the ends of the filament remains
a problem. If you dim halogen lamps, you may need "soft-start" devices in
order to achieve a major increase in bulb life.

Another problem with dimming of halogen lamps is the fact that the halogen
cycle works best with the bulb and filament at or near specific optimum
temperatures. If the bulb is dimmed, the halogen may fail to "clean" the
inner surface of the bulb. Or, tungsten halide that results may fail to
return tungsten to the filament.

Halogen bulbs should work normally at voltages as low as 90 percent of
what they were designed for. If the bulb is in an enclosure that conserves
heat and a "soft-start" device is used, it will probably work well at even
lower voltages, such as 80 percent or possibly 70 percent of its rated

Dimmers can be used as soft-start devices to extend the life of any
particular halogen bulbs that usually fail from "necking" of the ends of 
the filament. The bulb can be warmed up over a period of a couple of 
seconds to avoid overheating of the "necked" parts of the filament due to 
the current surge that occurs if full voltage is applied to a cold filament.
Once the bulb survives starting, it is operated at full power or 
whatever power level optimizes the halogen cycle (usually near full power).

The dimmer may be both "soft-starting" the bulb and operating it at slightly
reduced power, a combination that often improves the life of halogen bulbs.
Many dimmers cause some reduction in power to the bulb even when they are set
to maximum.

(A suggestion from someone who starts expensive medical lamps by turning up
a dimmer and reports major success in extending the life of expensive special
bulbs from doing this.)

  11.6) The humorous side of light bulbs

Also see the document: "Engineering, Science, and Other (Pretty Clean) Jokes
Collection" for all the light bulb jokes you could never want.

(From: Susanne Shavelson (shavelson@binah.cc.brandeis.edu)).

People have often mentioned experiencing epidemics of light-bulb-death
after moving into a new (to them) house.  The same thing happened to us
for a few months after moving last year into a 55-year-old house. After
most of the bulbs had been replaced, things settled down. I am persuaded
by the theory advanced by David (?) Owen in his wonderfully informative
and witty book "The Walls Around Us" that houses undergo a sort of nervous
breakdown when a new occupant moves in, leading to all sorts of symptoms
like blown bulbs, plumbing problems, cracks in the walls, and so forth.
Now that the house has become more accustomed to us, the rate at which
strange phenomena are occurring has slowed.

  11.7) Notes on bulb savers

These are usually either Negative Temperature Coefficient (NTC) thermisters
or simple diodes.

When cold, NTC thermisters have a high resistance.  As they warm up, the
resistance decreases so that the current to the light bulb is ramped up
gradually rather than being applied suddenly.

With a properly selected (designed) thermistor, I would not expect the
light output to be affected substantially.  However, while reducing the
power on surge may postpone the death of the bulb, the filament wear
mechanism is due to evaporation and redeposition of the tungsten during
normal operation.  This is mostly a function of the temperature of the

A thermistor which was not of low enough hot resistance would be dissipating
a lot of power - roughly .8 W/volt of drop for a 100W bulb.  Any really
substantial increase in bulb life would have to be due to this drop in voltage
and not the power-on surge reduction.  The bulb saver (and socket) would
also be heating significantly.

The bulb savers that are simply diodes do not have as much of a heat
dissipation problem but reduce the brightness substantially since the
bulbs are running at slightly over half wattage.  Not surprisingly, the
life does increase by quite a bit.  However, they are less efficient at
producing light at the lower wattage and it is more orange. If you are
tempted to then use a higher wattage bulb to compensate, you will
ultimately pay more than enough in additional electricity costs to
make up for the longer lived bulbs.

My recommendation: use high efficiency fluorescents where practical.
Use 130 V incandescents if needed in hard to reach places where bulb
replacement is a pain.  Stay away from bulb savers, green plugs, and
other similar products claiming huge energy reduction.  Your realized savings
for these products will rarely approach the advertised claims and you
risk damage to your appliances with some of these.

  11.8) Can you prove that bulb savers do not work?

No, sorry, I don't have conclusive proof.  I would love to be proved wrong - I
could save a lot on light bulbs.  However, new bulbs do not fail upon
power on.  Old bulbs do.  If you examine the filament of a well worn
light bulb, you will see a very distinct difference in surface appearance
compared to a brand new one.  The surface has gone from smooth to rough.
This change is caused by sustained operation at normal light bulb 
temperatures resulting in unequal evaporation of the filament.

Reducing the power on surge with a thermistor will reduce the mechanical
shock which will postpone the eventual failure.  5X or even 20 % increase
in life is pushing it IMHO.

I do believe that Consumer Reports has tested these bulb savers with
similar conclusions (however, I could be mistaken about the kind of
bulb savers they tested - it was quite awhile ago).

Chapter 12) Fluorescent Lamps, Ballasts, and Fixtures

Editor's note: This section is a condensed version of the document of the
same name available at: http://www.misty.com/~don/.  Special thanks to
Don Klipstein for help in editing of this material.

  12.1) Fluorescent lamp basics

The fluorescent lamp was the first major advance to be a commercial success
in small scale lighting since the tungsten incandescent bulb.  Its greatly
increased efficiency resulted in cool (temperature wise) brightly lit
workplaces (offices and factories) as well as home kitchens and baths.
The development of the mercury vapor high intensity discharge (HID) lamp
actually predates the fluorescent (the latter being introduced commercially
in 1938, four years after the HID).  However, HID type lamps have only
relatively recently become popular in small sizes for task lighting in
the home and office; yard and security area lighting; and light source
applications in overhead, computer, and video projectors.

Fluorescent lamps are a type of gas discharge tube similar to neon signs
and mercury or sodium vapor street or yard lights.  A pair of electrodes,
one at each end - are sealed along with a drop of mercury and some inert
gases (usually argon) at very low pressure inside a glass tube.  The
inside of the tube is coated with a phosphor which produces visible light
when excited with ultra-violet (UV) radiation.  The electrodes are in the
form of filaments which for preheat and rapid or warm start fixtures are
heated during the starting process to decrease the voltage requirements
and remain hot during normal operation as a result of the gas discharge
(bombardment by positive ions).

When the lamp is off, the mercury/gas mixture is non-conductive.  When power
is first applied, a high voltage (several hundred volts) is needed to initiate
the discharge.  However, once this takes place, a much lower voltage -
usually under 100 V is needed to maintain it.

The electric current passing through the low pressure gases (mainly
the mercury vapor) emits quite a bit of UV (but not much visible light).
The internal phosphor coating very efficiently converts most of the UV to
visible light.  The mix of the phosphor(s) is used to tailor the light
spectrum to the intended application.  Thus, there are cool white, warm
white, colored, and black light fluorescent (long wave UV) lamps.  There
are also lamps intended for medical or industrial uses with a special
envelope that passes short wave UV radiation such as quartz.  Some
have an uncoated envelope, and emit short-wave UV mercury radiation.
Others have phosphors that convert shortwave UV to medium wave UV.

CAUTION: many of these emit shortwave or medium wave UV which is
harmful and should not be used without appropriate protection in an
enclosure which prevents the escape of harmful UV radiation.

Fluorescent lamps are about 2-4 times as efficient as incandescent lamps
at producing light at the wavelengths that are useful to humans.  Thus,
they run cooler for the same effective light output.  The bulbs themselves
also last a lot longer - 10,000 to 20,000 hours vs. 1000 hours for a typical
incandescent.  However, for certain types of ballasts, this is only achieved
if the fluorescent lamp is left on for long periods of time without frequent
on-off cycles.

  12.2) Fluorescent lamp labeling

The actual fluorescent tubes are identified by several letters and numbers
and will look something like 'F40CW-T12' or 'FC12-T10'.

So, the typical labeling is of the form FSWWCCC-TDD (variations on this
format are possible):

F  -  Fluorescent lamp.
S  -  Style - no letter indicates normal straight tube; C for Circline.
WW -  Nominal power in Watts.  4, 5, 8, 12, 15, 20, 30, 40, etc.
CCC - Color.  W=White, CW=Cool white, WW=Warm white, BL/BLB=Black light, etc.
T  -  Tubular bulb.
DD -  Diameter of tube in of eighths of an inch.  T8 is 1", T12 is 1.5", etc.

For the most common T12 (1.5 inch) tube, the wattage (except for newer
energy saving types) is usually 5/6 of the length in inches.  Thus, an
F40-T12 tube is 48 inches long.

  12.3) Compact fluorescent bulbs

The compact fluorescent lamp is actually a fairly conventional fluorescent
tube packaged with an integral ballast (either iron or electronic) in
a standard screw base that can be installed into nearly any table lamp
or lighting fixture.

These types are being heavily promoted as energy savings alternatives
to incandescent lamps.  They also have a much longer life - up to 20,000
hours compared to 750 to 1000 hours for a standard incandescent.  While
these basic premises are not in dispute - all is not peaches and cream:

1.  They are often physically larger than the incandescent bulbs they replace
    and simply may not fit the lamp or fixture conveniently or at all.

2.  The funny elongated or circular shape may result in a less optimal
    lighting pattern.

3.  The light is generally cooler - less yellow - than incandescents - this
    may be undesirable and result in less than pleasing contrast with ordinary
    lamps and ceiling fixtures.  Newer models have been addressing this issue.

4.  Some types (usually iron ballasts) may produce an annoying 120 Hz
    (or 100 Hz) flicker.

5.  Ordinary dimmers cannot be used with compact fluorescents.

6.  Like other fluorescents, operation at cold temperatures (under 50 degrees
    F) may be erratic.

7.  There may be am audible buzz from the ballast.

8.  They may produce Radio Frequency Interference (RFI).

9.  The up-front cost is substantial (unless there is a large rebate): $10
    to $20 for a compact fluorescent to replace a 60 W incandescent bulb!

10. Due to the high up-front cost, the pay-back period may approach infinity.

11. While their life may be 20,000 hours, a wayward baseball will break
    one of these $10 to $20 bulbs as easily as a 25 cent incandescent.

Nonetheless, due to the lower energy use and cooler operation, compact
fluorescents do represent a desirable alternative to incandescents.  Just
don't open that investment account for all your increased savings just yet!

  12.4) Fluorescent fixtures

The typical fixture consists of:

* Lamp holder - the most common is designed for the straight bipin base bulb.
  The 12, 15, 24, and 48 inch straight fixtures are common in household and
  office use.  The 4 foot (48") type is probably the most widely used size.
  U shaped, circular (Circline(tm)), and other specialty tubes are also

* Ballast(s) - these are available for either 1 or 2 lamps.  Fixtures with
  4 lamps usually have two ballasts.  See the sections below on ballasts.
  The ballast performs two functions: current limiting and providing the
  starting kick to ionize the gas in the fluorescent tube(s).

* Switch - on/off control unless connected directly to building wiring in
  which case there will be a switch or relay elsewhere.  The power switch
  may have a momentary 'start' position if there is no starter and the
  ballast does not provide this function.

* Starter (preheat fixtures only) - device to initiate the high voltage
  needed for starting.  In other fixture types, the ballast handles this

  12.5) Fluorescent Lamp Ballasts

For a detailed explanation, check your library.  Here is a brief summary.

A ballast serves two functions:

1. Provide the starting kick.
2. Limit the current to the proper value for the tube you are using.

In the old days fluorescent fixtures had a starter or a power switch with
a 'start' position which is in essence a manual starter.  Some cheap ones
still do use this technology.

The starter is a time delay switch which when first powered, allows the
filaments at each end of the tube to warm up and then interrupts this part
of the circuit.  The inductive kick as a result of interrupting the current
through the inductive ballast provides enough voltage to ionize the gas
mixture in the tube and then the current through the tube keeps the
filaments hot - usually.  You will notice that a few iterations are sometimes
needed to get the tube to light.  The starter may keep cycling indefinitely
if either it or one of the tubes is faulty.  While the lamp is on, a
preheat ballast is just an inductor which at 60 Hz (or 50 Hz) has the
appropriate impedance to limit the current to the tube(s) to the proper value.

Ballasts must generally be fairly closely matched to the lamp in terms
tube wattage, length, and diameter.

  12.6) Types of iron ballasts

Instant start, trigger start, rapid start, etc. ballasts include loosely
coupled high voltage windings and other stuff and do away with the starter:

1. The ballast for a preheat fixture (using a starter or power switch with
   a 'start' position) is basically a series inductor.  Interrupting current
   through the inductor provides the starting voltage.

2. The ballast for an instant start fixture has a loosely coupled high
   voltage transformer winding providing about 500-600 V for starting
   in addition to the series inductor.

3. The ballast for a rapid start fixture has in addition small windings for
   heating the filaments reducing the required starting voltage to 250-400 V.
   Trigger start fixtures are similar to rapid start fixtures.

Starting voltage is either provided by the inductive kick upon interruption
of the current bypassed through the starter for (1) or a high voltage winding
in (2) and (3).

In all cases, the current limiting is provided primarily by the impedance
of the series inductance at 60 Hz (or 50 Hz depending on where you live).

  12.7) Electronic ballasts

These devices are basically switching power supplies that eliminate the
large, heavy, 'iron' ballast and replace it with an integrated high frequency
inverter/switcher.  Current limiting is then done by a very small 
inductor, which has sufficient impedance at the high frequency.  Properly
designed electronic ballasts should be very reliable.  Whether they actual
are reliable in practice depends on their location with respect to the heat
produced by the lamps as well as many other factors.  Since these ballasts
include rectification, filtering, and operate the tubes at a high frequency,
they also usually eliminate or greatly reduce the 120 Hz flicker associated
with iron ballasted systems.

I have heard, however, of problems with these relating to radio frequency
interference from the ballasts and tubes.  Other complaints have resulted
do to erratic behavior of electronic equipment using infra red remote controls.
There is a small amount of IR emission from the fluorescent tubes themselves
and this ends up being pulsed at the inverter frequencies which are similar
to those used by IR hand held remote controls.

  12.8) Wiring for preheat fluorescent fixtures

The following is the circuit diagram for a typical preheat lamp - one that
uses a starter or starting switch.

               Power Switch    +-----------+
  Line 1 (H) o------/ ---------|  Ballast  |------------+
                               +-----------+            |
                       .--------------------------.     |
  Line 2 (N) o---------|-       Fluorescent      -|-----+
                       | )         Tube         ( |
                   +---|-         (bipin)        -|-----+
                   |   '--------------------------'     |
                   |                                    |
                   |          +-------------+           |  
                   |          |   Starter   |           |
                   +----------| or starting |-----------+
                              |   switch    |

Here is a variation that some preheat ballasts use.  This type was found on
a F13-T5 lamp fixture:

               Power Switch   +-------------+
  Line 1 (H) o------/ --------|A  Ballast   |
                   +----------|B           C|-----------+
                   |          +-------------+           |
                   |                                    |
                   |   .--------------------------.     |
  Line 2 (N) o-----+---|-       Fluorescent      -|-----+
                       | )         Tube         ( |
                   +---|-         (bipin)        -|-----+
                   |   '--------------------------'     |
                   |                                    |
                   |          +-------------+           |  
                   |          |   Starter   |           |
                   +----------| or starting |-----------+
                              |   switch    |

  12.9) Fluorescent starter operation

The starter incorporates a switch which is normally open.  When power is
applied a glow discharge takes place which heats a bimetal contact.  A second
or so later, the contacts close providing current to the fluorescent filaments.
Since the glow is extinguished, there is no longer any heating of the
bimetal and the contacts open.  The inductive kick generated at the
instant of opening triggers the main discharge in the fluorescent tube.
off with the contacts open.  If the contacts open at a bad time - current
near zero, there isn't enough inductive kick and the process repeats.

Where a manual starting switch is used instead of an automatic starter,
there will be three switch positions:

OFF:   Both switches are open.
ON:    Power switch is closed.
START: (momentary) Power switch remains closed and starting switch in closed.

When released from the start position, the breaking of the filament circuit
results in an inductive kick as with the automatic starter which initiates
the gas discharge.

  12.10) Wiring for rapid start and trigger start fixtures

Rapid start and trigger start fixtures do not have a separate starter or
starting switch but use auxiliary windings on the ballast for this function.

The rapid start is now most common though you may find some labeled
trigger start as well.

Trigger start ballasts seem to be used for 1 or 2 small (12-20 W tubes).
Basic operation is very similar to that of rapid start ballasts and the
wiring is identical.

The ballast includes separate windings for the filaments and a high voltage
starting winding that is on a branch magnetic circuit that is loosely
coupled to the main core and thus limits the current once the arc is struck.

A reflector grounded to the ballast (and power wiring) is often required for
starting.  The capacitance of the reflector aids in initial ionization of the
gases.  Lack of this connection may result in erratic starting or the need
to touch or rum the tube to start.

A complete wiring diagram is usually provided on the ballast's case.

Power is often enabled via a socket operated safety interlock (x-x) to
minimize shock hazard.  However, I have seen normal (straight) fixtures
which lack this type of socket even where ballast labeling requires it.
Circline fixtures do not need an interlock since the connectors are fully
enclosed - it is not likely that there could be accidental contact with
a pin while changing bulbs.

Below is the wiring diagram for a single lamp rapid or trigger start
ballast.  The color coding is fairly standard.  The same ballast could
be used for an F20-T12, F15-T12, F15-T8, or F14-T12 lamp.  A similar
ballast for a Circline fixture could be used with an FC16-T10 or
lamp FC12-T10 (no interlock).

 Line 2 (N) o----------------|Black  Rapid/Trigger      |
                       +-----|White      Start       Red|-----+
                       |  +--|Blue      Ballast      Red|--+  |
                       |  |  +-------------+------------+  |  |
                       |  |                |               |  |
                       |  |       Grounded | Reflector     |  |
                       |  |      ----------+----------     |  |
                       |  |    .----------------------.    |  |
                       |  +----|-     Fluorescent    -|----+  |
                       +------x| )       Tube       ( |       |
 Line 1 (H) o----/ -----------x|-  (bipin or circ.)  -|-------+
             Power Switch      '----------------------'

The following wiring diagram is for one pair (from a 4 tube fixture)
of a typical rapid start 48 inch fixture.  These ballasts specify the
bulb type to be F40-T12 RS.  There is no safety interlock on this

             Power Switch    +--------------------------+
 Line 1 (H) o----/ ----------|Black    Dual Tube     Red|-----------+
 Line 2 (N) o----------------|White      Rapid       Red|--------+  |
                       +-----|Yellow     Start      Blue|-----+  |  |
                       |  +--|Yellow    Ballast     Blue|--+  |  |  |
                       |  |  +-------------+------------+  |  |  |  |
                       |  |                |               |  |  |  |
                       |  |       Grounded | Reflector     |  |  |  |
                       |  |      ----------+----------     |  |  |  |
                       |  |    .----------------------.    |  |  |  |
                       |  +----|-     Fluorescent    -|----+  |  |  |
                       |  |    | )      Tube 1      ( |       |  |  |
                       +-------|-       bipin        -|-------+  |  |
                       |  |    '----------------------'          |  |
                       |  |    .----------------------.          |  |
                       |  +----|-     Fluorescent    -|----------+  |
                       |       | )      Tube 2      ( |             |
                       +-------|-       bipin        -|-------------+

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Written by Samuel M. Goldwasser. | [mailto]. The most recent version is available on the WWW server http://www.repairfaq.org/ [Copyright] [Disclaimer]