Notes on the Troubleshooting and Repair of Computer and Video Monitors


  3.3) On-line tech-tips databases

A number of organizations have compiled databases covering thousands of common
problems with VCRs, TVs, computer monitors, and other electronics equipment.
Most charge for their information but a few, accessible via the Internet, are
either free or have a very minimal monthly or per-case fee.  In other cases, a
limited but still useful subset of the for-fee database is freely available.

A tech-tips database is a collection of problems and solutions accumulated by
the organization providing the information or other sources based on actual
repair experiences and case histories.  Since the identical failures often
occur at some point in a large percentage of a given model or product line,
checking out a tech-tips database may quickly identify your problem and

In that case, you can greatly simplify your troubleshooting or at least
confirm a diagnosis before ordering parts.  My only reservation with respect
to tech-tips databases in general - this has nothing to do with any one in
particular - is that symptoms can sometimes be deceiving and a solution that
works in one instance may not apply to your specific problem.  Therefore,
an understanding of the hows and whys of the equipment along with some good
old fashioned testing is highly desirable to minimize the risk of replacing
parts that turn out not to be bad.

The other disadvantage - at least from one point of view - is that you do not
learn much by just following a procedure developed by others.  There is no
explanation of how the original diagnosis was determined or what may have
caused the failure in the first place.  Nor is there likely to be any list
of other components that may have been affected by overstress and may fail
in the future.  Replacing Q701 and C725 may get your equipment going again
but this will not help you to repair a different model in the future.

Having said that, here are three tech-tips sites for computer monitors, TVs,
and VCRs:

* http://www.anatekcorp.com/techforum.htm            (Free).
* http://www.repairworld.com/                        ($8/month).
* http://elmswood.guernsey.net/                      (Free, somewhat limited).

The following is just for monitors.  Some portions are free but others require
a $5 charge.  However, this may include a personal reply from a technician
experienced with your monitor so it could be well worth it.

* http://www.netis.com/members/bcollins/monitor.htm

Some free monitor repair tips:

* http://www.kmrtech.com/
* http://www.metrosites.com/amr/monitor_repair_tips.htm

Tech-tips of the month and 'ask a wizard' options:

* http://members.tripod.com/~ADCC/          (Home page)
* http://members.tripod.com/~ADCC/tips.htm  (Tech-tips of the month)

The Resolve Monitor Tech-Tips database is a diskette that is priced out of
the reach of most hobbyists.  However, a reduced shareware version may be
downloaded from a number of web sites.  Go to http://www.filez.com/ and look
for res16sw.zip.

Chapter 4) CRT Basics

Note: Most of the information on TV and monitor CRT construction, operation,
interference and other problems. has been moved to the document: "TV and
Monitor CRT (Picture Tube) Information".  The following is just a brief
introduction with instructions on degaussing.

  4.1) Color CRTs - shadow masks and aperture grills

All color CRTs utilize a shadow mask or aperture grill a fraction of an inch
(1/2" typical) behind the phosphor screen to direct the electron beams 
for the red, green, and blue video signals to the proper phosphor dots.
Since the electron beams for the R, G, and B phosphors originate from
slightly different positions (individual electron guns for each)
and thus arrive at slightly different angles, only the proper phosphors
are excited when the purity is properly adjusted and the necessary
magnetic field free region is maintained inside the CRT.  Note that
purity determines that the correct video signal excites the
proper color while convergence determines the geometric
alignment of the 3 colors.  Both are affected by magnetic fields.
Bad purity results in mottled or incorrect colors.  Bad convergence
results in color fringing at edges of characters or graphics.

The shadow mask consists of a thin steel or InVar (a ferrous alloy)
with a fine array of holes - one for each trio of phosphor
dots - positioned about 1/2 inch behind the surface of the phosphor
screen.  With some CRTs, the phosphors are arranged in triangular
formations called triads with each of the color dots at the apex
of the triangle.  With many TVs and some monitors, they are
arranged as vertical slots with the phosphors for the 3 colors
next to one another.

An aperture grille, used exclusively in Sony Trinitrons (and now
their clones as well), replaces the shadow mask with an array of finely
tensioned vertical wires.  Along with other characteristics of the
aperture grille approach, this permits a somewhat higher possible
brightness to be achieved and is more immune to other problems like
line induced moire and purity changes due to local heating causing
distortion of the shadow mask.

However, there are some disadvantages of the aperture grille design:

* weight - a heavy support structure must be provided for the tensioned
  wires (like a piano frame).

* price (proportional to weight).

* always a cylindrical screen (this may be considered an advantage
  depending on your preference.

* visible stabilizing wires which may be objectionable or unacceptable
  for certain applications.

Apparently, there is no known way around the need to keep the fine
wires from vibrating or changing position due to mechanical shock
in high resolution tubes and thus all Trinitron monitors require
1, 2, or 3 stabilizing wires (depending on tube size) across the 
screen which can be see as very fine lines on bright images.  Some
people find these wires to be objectionable and for some critical
applications, they may be unacceptable (e.g., medical diagnosis).

  4.2) Degaussing (demagnetizing) a CRT

Degaussing may be required if there are color purity problems with the
display.  On rare occasions, there may be geometric distortion caused
by magnetic fields as well without color problems.  The CRT can get

* if the TV or monitor is moved or even just rotated.

* if there has been a lightning strike nearby.  A friend of mine
  had a lightning strike near his house which produced all of the
  effects of the EMP from a nuclear bomb.

* If a permanent magnet was brought near the screen (e.g., kid's
  magnet or megawatt stereo speakers).

* If some piece of electrical or electronic equipment with unshielded
  magnetic fields is in the vicinity of the TV or monitor.  

Degaussing should be the first thing attempted whenever color
purity problems are detected.  As noted below, first try the
internal degauss circuits of the TV or monitor by power cycling a few
times (on for a minute, off for 30 minutes, on for a minute, etc.)
If this does not help or does not completely cure the problem,
then you can try manually degaussing.

Commercial CRT Degaussers are available from parts distributors
like MCM Electronics and consist of a hundred or so turns of magnet wire
in a 6-12 inch coil.  They include a line cord and momentary switch. You 
flip on the switch, and bring the coil to within several inches of the 
screen face. Then you slowly draw the center of the coil toward one edge 
of the screen and trace the perimeter of the screen face. Then return to 
the original position of the coil being flat against the center of the 
screen.  Next, slowly decrease the field to zero by backing straight up 
across the room as you hold the coil. When you are farther than 5 feet 
away you can release the line switch. 

The key word here is ** slow **.  Go too fast and you will freeze the
instantaneous intensity of the 50/60 Hz AC magnetic field variation
into the ferrous components of the CRT and may make the problem worse.

It looks really cool to do this while the CRT is powered.  The kids will
love the color effects.

Bulk tape erasers, tape head degaussers, open frame transformers, and the
"ass-end" of a weller soldering gun can be used as CRT demagnetizers but
it just takes a little longer. (Be careful not to scratch the screen
face with anything sharp.) It is imperative to have the CRT running when
using these whimpier approaches, so that you can see where there are 
still impurities. Never release the power switch until you're 4 or 5 
feet away from the screen or you'll have to start over.

I've never known of anything being damaged by excess manual degaussing
though I would recommend keeping really powerful bulk tape erasers turned
degaussers a couple of inches from the CRT.

If an AC degaussing coil or substitute is unavailable, I have even done
degaussed with a permanent magnet but this is not recommended since it is more
likely to make the problem worse than better.  However, if the display
is unusable as is, then using a small magnet can do no harm. (Don't use
a 20 pound speaker or magnetron magnet as you may rip the shadow mask right
out of the CRT - well at least distort it beyond repair.  What I have in
mind is something about as powerful as a refrigerator magnet.)

Keep degaussing fields away from magnetic media.  It is a good idea to
avoid degaussing in a room with floppies or back-up tapes.  When removing
media from a room  remember to check desk drawers and manuals for stray
floppies, too. 

It is unlikely that you could actually affect magnetic media but better
safe than sorry.  Of the devices mentioned above, only a bulk eraser or
strong permanent magnet are likely to have any effect - and then only when
at extremely close range (direct contact with media container).

All color CRTs include a built-in degaussing coil wrapped around the 
perimeter of the CRT face. These are activated each time the CRT is 
powered up cold by a 3 terminal thermister device or other control
circuitry.  This is why it is often suggested that color purity problems
may go away "in a few days".  It isn't a matter of time; it's the number
of cold power ups that causes it.  It takes about 15 minutes of the power
being off for each cool down cycle. These built-in coils with thermal
control are never as effective as external coils.

See the document: " TV and Monitor CRT (Picture Tube) Information" for
some additional discussion of degaussing tools, techniques, and cautions.

  4.3) How often to degauss

Some monitor manufacturers specifically warn about excessive use of degauss,
most likely as a result of overstressing components in the degauss circuitry
which are designed (cheaply) for only infrequent use.  In particular,
there is often a thermister that dissipates significant power for the second
or two that the degauss is active.  Also, the large coil around the CRT
is not rated for continuous operation and may overheat.

If one or two activations of the degauss button do not clear up the color
problems, manual degaussing using an external coil may be needed
or the monitor may need internal purity/color adjustments.  Or, you may have
just installed your megawatt stereo speakers next to the monitor!

You should only need to degauss if you see color purity problems
on your CRT.  Otherwise it is unnecessary.  The reasons it only works the
first time is that the degauss timing is controlled by a termister
which heats up and cuts off the current.  If you push the button
twice in a row, that thermister is still hot and so little happens.

One word of clarification:  In order for the degauss operation to be
effective, the AC current in the coil must approach zero before the
circuit cuts out.  The circuit to accomplish this often involves a 
thermister to gradually decrease the current (over a matter of several
seconds), and in better monitors, a relay to totally cut off the current
after a certain delay.  If the current was turned off suddenly, you would
likely be left with a more magnetized CRT.  There are time delay elements
involved which prevent multiple degauss operations in succession.  Whether
this is by design or accident, it does prevent the degauss coil - which is
usually grossly undersized for continuous operation - to cool.

  4.4) Why are there fine lines across my Trinitron monitor or TV?

These are not a defect - they are a 'feature'.

All Trinitron (or clone) CRTs - tubes that use an aperture grille - require
1, 2, or 3 very fine wires across the screen to stabilize the array of
vertical wires in the aperture grille.  Without these, the display would
be very sensitive to any shock or vibration and result in visible shimmering
or rippling.  (In fact, even with these stabilizing wires, you can usually
see this shimmering if you whack a Trinitron monitor.)  The lines you see
are the shadows cast by these fine wires.

The number of wires depends on the size of the screen.  Below 15" there
is usually a single wire; between 15" and 21" there are usually 2 wires;
above 21" there may be 3 wires.

Only you can decide if this deficiency is serious enough to avoid the
use of a Trinitron based monitor.  Some people never get used to the fine
lines but many really like the generally high quality of Trinitron based
displays and eventually totally ignore them.

Chapter 5) Monitor Placement and Preventive Maintenance

  5.1) General monitor placement considerations

Proper care of a monitor does not require much.  Following the recommendations
below will assure long life and minimize repairs:

* Subdued lighting is preferred for best viewing conditions.  Avoid direct
  overhead light falling on the screen or coming from behind the monitor
  if possible.

* Locate the monitor away from extremes of hot and cold.  Avoid damp or dusty
  locations if possible.  (Right you say, keep dreaming!)  This will help
  keep your PC happy as well.

* Allow adequate ventilation - monitors use a fair amount of power - from
  60 watts for a 12 inch monochrome monitor to over 200 W for a 21 inch
  high resolution color monitor.  Heat is one major enemy of electronics.

* Do not put anything on top of the monitor that might block the ventilation
  grill in the rear or top of the cover.  This is the major avenue for
  the convection needed to cool internal components.

* Do not place two monitors close to one another.  The magnetic fields
  may cause either or both to suffer from wiggling or shimmering images.
  Likewise, do not place a monitor next to a TV if possible.

* Locate loudspeakers and other sources of magnetic fields at least a couple
  of feet from the monitor.  This will minimize the possibility of color purity
  or geometry problems.  The exception is with respect to good quality shielded
  multimedia speakers which are designed to avoid magnetic interference

  Other devices which may cause interference include anything with power
  transformers including audio equipment, AC or DC wall adapters, and laptop
  power supplies; fluorescent lamps with magnetic ballasts; and motorized
  or heavy duty appliances.

* Situate monitors away from power lines - even electric wiring behind
  or on the other side of walls - and heavy equipment which may cause
  noticeable interference like rippling, wiggling, or swimming of the
  picture.  Shielding is difficult and expensive.

* Make sure all video connections are secure (tighten the thumbscrews)
  to minimize the possibility of intermittent or noisy colors.  Keep the
  cables as short as possible.  Do not add extension cables if at all
  possible as these almost always result in a reduction in image crispness
  and introduce ghosting, smearing, and other termination problems.
  If you must add an extension, use proper high quality cable only long
  enough to make connections conveniently.  Follow the termination 
  recommendations elsewhere in this document.

* Finally, store magnetic media well away from all electronic equipment
  including and especially monitors and loudspeakers.  Heat and magnetic
  fields will rapidly turn your diskettes and tapes into so much trash.  The
  operation of the monitor depends on magnetic fields for beam deflection. 
  Enough said.

  5.2) Non-standard monitor mounting considerations

Monitors normally are positioned horizontally or via the limits of their tilt
swivel bases out in the open on a table or desktop.  However, for use in
exhibits or for custom installations, it may be desirable to mount a monitor
in a non-standard position and/or inside an enclosure.

(From: Bob Myers (myers@fc.hp.com)).

Your mileage may vary, but (and please take the following for what it is, a
very general answer)...

There are basically two potential problems here; one is cooling, and the other
is the fact that the monitor has no doubt been set up by the factory assuming
standard magnetic conditions, which probably DIDN'T involve the monitor
tilting at much of an angle.  If you're happy with the image quality when it's
installed in the cabinet, that leaves just the first concern.  THAT one can be
addressed by simply making sure the cabinet provides adequate ventilation (and
preferably adding a fan for a bit of forced-air cooling), and making sure that
the whole installation isn't going to be exposed to high ambient temperatures.
(Most monitors are speced to a 40 deg. C ambient in their normal orientation;
adding forced-air cooling will usually let you keep that rating in positions
somewhat beyond the normal.)  Under no circumstances should you block the
cabinet's vents, and - depending on the installation - it may be preferable to
remove the rear case parts of the monitor (but NOT the metal covers beneath
the plastic skin) in order to improve air circulation.

Your best bet is to simply contact the service/support people of the monitor
manufacturer, and get their input on the installation.  Failing to get the
manufacturer's blessing on something like this most often voids the warranty,
and can probably lead to some liability problems.  (Note - I'm not a lawyer,
and I'm not about to start playing one on the net.)

  5.3) Preventive maintenance - care and cleaning

Preventive maintenance for a monitor is pretty simple - just keep the case
clean and free of obstructions.  Clean the CRT screen with a soft cloth just
dampened with water and mild detergent or isopropyl alcohol.  This will
avoid damage to normal as well as antireflection coated glass.  DO NOT use
anything so wet that liquid may seep inside of the monitor around the edge
of the CRT.  You could end up with a very expensive repair bill when the
liquid decides to short out the main circuit board lurking just below.
Then dry thoroughly.  Use the CRT sprays sold in computer stores if you
like but again, make sure none can seep inside.  If you have not cleaned
the screen for quite a while, you will be amazed at the amount of black
grime that collects due to the static buildup from the CRT high voltage

In really dusty situations, periodically vacuuming inside the case and the use
of contact cleaner for the controls might be a good idea but realistically,
you will not do this so don't worry about it.

(From: Tom Watson (tsw@johana.com)).

If you are maintaining a site, consider periodic cleaning of the monitors.
Depending on the location, they can accumulate quite a bit of dust.  In normal
operation there is a electrostatic charge on the face of the crt (larger
screens have bigger charges) which act as 'dust magnets'. If the operator
smokes (thankfully decreasing), it is even worse.  At one site I helped out
with, most of the operators smoked, and the screens slowly got covered with a
film of both dust and smoke particles.  A little bit of glass cleaner applied
with reasonable caution and the decree of "adjustments" to make the screen
better (these were character monochrome terminals), and lo and behold, "what
an improvement!". Yes, even in my dusty house, the TVs get a coating of
film/goo which needs to be cleaned, and the picture quality (BayWatch viewers
beware) improves quite a bit.  Try this on your home TV to see what comes off,
then show everyone else.  You will be surprised what a little bit of cleaning

(From: Bob Myers (myers@fc.hp.com)).

1. Don't block the vents; make sure the monitor has adequate ventilation,
   and don't operate it more than necessary at high ambient temperatures.

2. If the monitor is used in particularly dusty environments, it's probably
   a good idea to have a qualified service tech open it up every so often
   (perhaps once a year, or more often depending on just how dirty it gets)
   and clean out the dust.

3. The usual sorts of common-sense things - don't subject the monitor to
   mechanical shock and vibration, clean up spills, etc., promptly, and
   so forth.  And if you're having repeated power-supply problems with your
   equipment, it may be time to get suspicious of the quality of your AC
   power (are you getting noise on the line, sags, surges, spikes, brownouts,
   that sort of thing?).

And most importantly:

4. Turn the monitor OFF when it's not going to be used for an extended
   period (such as overnight, or if you'll be away from your desk for the
   afternoon, etc.).  Heat is the enemy of all electronic components, and
   screen-savers do NOTHING in this regard.  Many screen-savers don't even
   do a particularly good job of going easy on the CRT.  With modern
   power-management software, there's really no reason to be leaving a
   monitor up and running all the time.

These won't guarantee long life, of course - nothing can do that, as there
will always be the possibility of the random component failure.  But these
are the best that the user can do to make sure the monitor goes as long as
it can.

  5.4) Monitor tuneup?

(From: Bob Myers (myers@fc.hp.com)).

Most manufacturers will quote an MTBF (Mean Time Before Failure) of
somewhere in the 30,000 to 60,000 hour range, EXCLUSIVE OF the CRT.  The
typical CRT, without an extended-life cathode, is usually good for 
10,000 to 15,000 hours before it reaches half of its initial brightness.
Note that, if you leave your monitor on all the time, a year is just about
8,000 hours.

The only "tuneup" that a monitor should need, exclusive of adjustments
needed following replacement of a failed component, would be video amplifier
and/or CRT biasing adjustments to compensate for the aging of the tube.
These are usually done only if you're using the thing in an application where
exact color/brightness matching is important.  Regular degaussing of the
unit may be needed, of course, but I'm not considering that a "tuneup" or

Chapter 6) Monitor Troubleshooting

  6.1) SAFETY

TVs and computer or video monitors are among the more dangerous of consumer
electronics equipment when it comes to servicing.  (Microwave ovens are
probably the most hazardous due to high voltage at flesh frying and cardiac
arresting high power.)

There are two areas which have particularly nasty electrical dangers: the
non-isolated line power supply and the CRT high voltage.

Major parts of nearly all modern TVs and many computer monitors are directly
connected to the AC line - there is no power transformer to provide the
essential barrier for safety and to minimize the risk of equipment damage.
In the majority of designs, the live parts of the TV or monitor are limited
to the AC input and line filter, degauss circuit, bridge rectifier and main
filter capacitor(s), low voltage (B+) regulator (if any), horizontal output
transistor and primary side of the flyback (LOPT) transformer, and parts
of the startup circuit and standby power supply.  The flyback generates most
of the other voltages used in the unit and provides an isolation barrier so
that the signal circuits are not line connected and safer.

Since a bridge rectifier is generally used in the power supply, both
directions of the polarized plug result in dangerous conditions and an
isolation transformer really should be used - to protect you, your test
equipment, and the TV, from serious damage.  Some TVs do not have any
isolation barrier whatsoever - the entire chassis is live.  These are
particularly nasty.

The high voltage to the CRT, while 200 times greater than the line input,
is not nearly as dangerous for several reasons.  First, it is present in a
very limited area of the TV or monitor - from the output of the flyback
to the CRT anode via the fat red wire and suction cup connector.  If you
don't need to remove the mainboard or replace the flyback or CRT, then
leave it alone and it should not bite.  Furthermore, while the shock from
the HV can be quite painful due to the capacitance of the CRT envelope, it
is not nearly as likely to be lethal since the current available from the
line connected power supply is much greater.

  6.2) Safety Guidelines

These guidelines are to protect you from potentially deadly electrical shock
hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting
path, particularly through your heart.  Any involuntary muscle contractions
caused by a shock, while perhaps harmless in themselves, may cause collateral
damage - there are many sharp edges inside this type of equipment as well as
other electrically live parts you may contact accidentally.

The purpose of this set of guidelines is not to frighten you but rather to
make you aware of the appropriate precautions.  Repair of TVs, monitors,
microwave ovens, and other consumer and industrial equipment can be both
rewarding and economical.  Just be sure that it is also safe!

* Don't work alone - in the event of an emergency another person's presence
  may be essential.

* Always keep one hand in your pocket when anywhere around a powered
  line-connected or high voltage system.

* Wear rubber bottom shoes or sneakers.

* Don't wear any jewelry or other articles that could accidentally contact
  circuitry and conduct current, or get caught in moving parts.

* Set up your work area away from possible grounds that you may accidentally

* Know your equipment: TVs and monitors may use parts of the metal chassis
  as ground return yet the chassis may be electrically live with respect to the
  earth ground of the AC line.  Microwave ovens use the chassis as ground
  return for the high voltage.  In addition, do not assume that the chassis
  is a suitable ground for your test equipment!

* If circuit boards need to be removed from their mountings, put insulating
  material between the boards and anything they may short to.  Hold them in
  place with string or electrical tape.  Prop them up with insulation sticks -
  plastic or wood.

* If you need to probe, solder, or otherwise touch circuits with power off,
  discharge (across) large power supply filter capacitors with a 2 W or greater
  resistor of 100 to 500 ohms/V approximate value (e.g., for a 200 V capacitor,
  use a 20K to 100K ohm resistor).  Monitor while discharging and verify that
  there is no residual charge with a suitable voltmeter.  In a TV or monitor,
  if you are removing the high voltage connection to the CRT (to replace the
  flyback transformer for example) first discharge the CRT contact (under the
  insulating cup at the end of the fat red wire).  Use a 1M to 10M ohm 5 W or
  greater wattage (for its voltage holdoff capability, not power dissipation)
  resistor on the end of an insulating stick or the probe of a high voltage
  meter.  Discharge to the metal frame which is connected to the outside of
  the CRT.

* For TVs and monitors in particular, there is the additional danger of
  CRT implosion - take care not to bang the CRT envelope with your tools.
  An implosion will scatter shards of glass at high velocity in every
  direction.  There are several tons of force attempting to crush the typical
  CRT.  While implosion is not really likely even with modest abuse, why take
  chances?  However, the CRT neck is relatively thin and fragile and breaking
  it would be very embarrassing and costly.  Always wear eye protection when
  working around the back side of a CRT.

* Connect/disconnect any test leads with the equipment unpowered and
  unplugged. Use clip leads or solder temporary wires to reach cramped
  locations or difficult to access locations.

* If you must probe live, put electrical tape over all but the last 1/16"
  of the test probes to avoid the possibility of an accidental short which
  could cause damage to various components.  Clip the reference end of the
  meter or scope to the appropriate ground return so that you need to only
  probe with one hand.

* Perform as many tests as possible with power off and the equipment unplugged.
  For example, the semiconductors in the power supply section of a TV or
  monitor can be tested for short circuits with an ohmmeter.

* Use an isolation transformer if there is any chance of contacting line
  connected circuits.  A Variac(tm) is not an isolation transformer!
  The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a
  good idea but will not protect you from shock from many points in a line
  connected TV or monitor, or the high voltage side of a microwave oven, for
  example.  (Note however, that, a GFCI may nuisanse trip at power-on or at
  other random times due to leakage paths (like your scope probe ground) or
  the highly capacitive or inductive input characteristics of line powered
  equipment.)  A fuse or circuit breaker is too slow and insensitive to provide
  any protection for you or in many cases, your equipment.  However, these
  devices may save your scope probe ground wire should you accidentally connect
  it to a live chassis.

* Don't attempt repair work when you are tired.  Not only will you be more
  careless, but your primary diagnostic tool - deductive reasoning - will
  not be operating at full capacity.

* Finally, never assume anything without checking it out for yourself!
  Don't take shortcuts!

  6.3) Troubleshooting tips

Many problems have simple solutions.  Don't immediately assume that
your problem is some combination of esoteric complex convoluted
failures.  For a monitor, it may just be a bad connection or blown fuse.
Remember that the problems with the most catastrophic impact on operation
like a dead monitor usually have the simplest solutions.  The kind of
problems we would like to avoid at all costs are the ones that are
intermittent or difficult to reproduce: the occasional jitter or a monitor
that blows its horizontal output transistor every six months.

If you get stuck, sleep on it.  Sometimes, just letting the problem
bounce around in your head will lead to a different more successful
approach or solution.  Don't work when you are really tired - it is both
dangerous (especially with respect to monitors) and mostly non-productive
(or possibly destructive).

Whenever working on complex equipment, make copious notes and diagrams.
You will be eternally grateful when the time comes to reassemble the unit.
Most connectors are keyed against incorrect insertion or interchange
of cables, but not always.  Apparently identical screws may be of differing
lengths or have slightly different thread types.  Little parts may fit in
more than one place or orientation.  Etc.  Etc.

Pill bottles, film canisters, and plastic ice cube trays come in handy for
sorting and storing screws and other small parts after disassembly.  This
is particularly true if you have repairs on multiple pieces of equipment
under way simultaneously.

Select a work area which is wide open, well lighted, and where dropped
parts can be located - not on a deep pile shag rug.  The best location will
also be relatively dust free and allow you to suspend your troubleshooting
to eat or sleep or think without having to pile everything into a cardboard
box for storage.

Another consideration is ESD - Electro-Static Discharge.  Some components
(like ICs) in a TV are vulnerable to ESD.  There is no need to go overboard
but taking reasonable precautions such as getting into the habit of touching
a **safe** ground point first.

WARNING: even with an isolation transformer, a live chassis should **not** be
considered a safe ground point.  When the monitor is unplugged, the shields
or other signal ground points should be safe and effective.

A basic set of precision hand tools will be all you need to disassemble
a monitor and perform most adjustments.  These do not need to be really
expensive but poor quality tools are worse than useless and can cause
damage.  Needed tools include a selection of Philips and straight blade
screwdrivers, socket drivers, needlenose pliers, wire cutters, tweezers,
and dental picks.  For adjustments, a miniature (1/16" blade) screwdriver
with a non-metallic tip is desirable both to prevent the presence of
metal from altering the electrical properties of the circuit and to
minimize the possibility of shorting something from accidental contact
with the circuitry.  A set of plastic alignment tools will be useful for
making adjustments to coils (though you can forgo these until the (rare)
need arises.

A low power (e.g., 25 W) fine tip soldering iron and fine rosin core solder
will be needed if you should need to disconnect any soldered wires (on purpose
or by accident) or replace soldered components.  A higher power iron or small
soldering gun will be needed for dealing with larger components.  Never use
acid core solder or the type used for sweating copper pipes!

See the document: "Troubleshooting and Repair of Consumer Electronics
Equipment" for additional info on soldering and rework techniques.

For thermal or warmup problems, a can of 'cold spray' or 'circuit chiller'
(they are the same) and a heat gun or blow dryer come in handy to identify
components whose characteristics may be drifting with temperature.  Using the
extension tube of the spray can or making a cardboard nozzle for the heat
gun can provide very precise control of which components you are affecting.

For info on useful chemicals, adhesives, and lubricants, see "Repair Briefs,
an Introduction" as well as other documents available at this site.

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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]