Notes On The Troubleshooting And Repair Of Television Sets


  26.9) Channel tuning drifts as set warms up

This may be a slight drift - like someone is messing with the fine tuning
or such a substantial change in tuning frequency that the channels go by
as though you are surfing.

Possible causes depend on tuner type:

1. Quartz tuner (10 button direct access digital synthesizer) - For a
   slight drift, a component is probably changing value, possibly the
   crystal in the reference oscillator.  For gross changes - flipping
   through channels - it is more likely to be a digital control problem -
   the microcontroller is misdirecting the synthesizer to change frequency.

2. Varactor tuner (buttons but not direct channel access) - If only a
   single pushbutton selection is the problem, the the varactor tuning diode
   for that button is probably changing capacitance.  If all channels in
   a band (Vl, Vh, U) are having a problem, it is more likely to be a
   drifting D/A or faulty AFT (Automatic Fine Tuning) circuit or power supply.

3. Turret or switch tuner (Knobs) - A component like a capacitor is changing

You will have to get in there with a heat gun or cold spray and track it down
the old fashioned way.  At least, the problem is almost certainly localized
to the tuner box (and possibly the controller if applicable).

As noted, gradual slight changes in tuning are likely due to frequency
determining components drifting.

Uncontrolled channel surfing is probably a logic problem.   For the
quartz tuner, this could still be marginal connections causing the
microprocessor to misdirect the synthesizer to change channels.

For the latter case, particularly, the cause may still be bad connections
resulting in loss of channel memory and/or erratic behavior.

  26.10) Noise in picture and sound due to bright scene

When a bright scene comes, the screen flashes and there is a lot
of noise in the sound.  When a dark scene comes, there is no 
flash or noise.  Changing channel does not help.  The noise 
persists even when the sound is muted.

(The following is from: Lattuca@Midwest.net (Sam Lattuca))

When the video detector level is adjusted too high, you will get noise in 
the sound while screen contains a lot of white information (i.e. letters) but 
won't when only dark scenes are present. The video level adjust is usually a 
small coil normally located near the IF section. Since your set is several 
years old, this wouldn't be uncommon. It can be adjusted while watching the 
picture and listening to the sound.

  26.11) Internal interference - switchmode power supplies and digital circuitry

(From: Mr. Caldwell (jcaldwel@iquest.net)).

On virtually all newer televisions and in particular Mitsubishi televisions
there is a problem with interference being emitted by the switched mode power

The common symptom of this 'fault' is snake like dotted 'S' lines on channels
2-6. It doesn't matter if it's cable, antenna or satellite(channel 3/4), this
symptom can occur.

The common cause of this interference being allowed into the tuner is cabling.
The super cheap 'suitable for garbage tie' cable that comes with even the most
expensive VCR's is the culprit in most cases. The second is a set of rabbit
ears the least common is an open or high resistance to ground connection
(usually at a connector) on the incoming cable line.

To fix this there is only one reliable solution. All cabling must be hand made
RG-6 cable. Make as follows: 

* Strip the outer sheath of the cable to expose the braid and *fold the braid*
  away from the end so that it covers the unstripped outer braid. 

* Strip the inner conductor to it's proper length.

* Install a good quality RG-6 connector *over the folded* braid.

* Crimp with the proper RG-6 attachment to the cable crimpers, don't use a
  set of pliers or other -crushing- device.

If the cable company doesn't water proof the outside connectors, Radio Shack
sells a 'sealing tape' just for this purpose. Most cable companies use self 
sealing 'o-ring' connectors.  

(From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)).

There is also interference from internal microprocessors and digital
text generators (on-screen display, close captioning, teletext).
And with 100 Hz digital television there is a wealth of sources ...

Using only high quality shielded cable as described above seems like really
good advise, FWIW I'd like to second that.  I wish that everyone would take
antenna cables as seriously as you.

Generally, double-braided cable (using copper foil for second shield) and
coaxially constructed connectors are recommended.  But I think that the
hand-mountable F-type connectors (Radio Shack) would be equally good, though
less robust, if mounted properly.

As far as antennas go, a decent rooftop antenna should always be better than
whatever rabbit ear construction you might think of. In this case, distance
counts too, the antenna WILL pick up interference.

  26.12) Those darn rabbit ears

So you bought a high performance TV and a set of $20.00 rabbit ears and there
are lines on channels 2-6. Go buy a set of rabbit ears that has *only* a coax
connector on the back, throw the cable supplied with it in the bin for 'twist
ties'.  Also buy an inexpensive surge suppressor that has a cable protector,
enough RG-6 cable and connectors for two cables.

* Make one cable long enough to get the antenna away from the set (12ft) and
  the other to connect the antenna to the surge suppressor.

* Connect the long cable to the set and the other end to the surge suppressor.

* Find an outlet away from the set and plug the surge suppressor in (pick the
  most sane order for all of this.)

* Connect the shorter cable to the surge suppressor and connect the other end
  to the antenna.

You're done and if you thought carefully you would have put the antenna near
your easy chair so you can adjust the picture or put the antenna where you'll
get the best reception and prevent interference. The surge suppressor was
needed to ground the other end of the coax so as not to make the outer shield
an antenna for the interference from the TV's power supply. This method can
also help allevate 'dead spots' when using rabbit ears.

  26.13) Herringbone lines in picture

(From: Isaac Bergen (isaac.bergen@sympatico.ca)).

Could be interference. If the pattern slowly moves up the screen, the 
problem is from the 60 Hz power. A line of dots or thin lines usually 
means corona discharge (arcing) from a nearby power line (especially on 
humid days). Could also be from a bad filter capacitor in the TV's power 
supply. A "checkered" pattern could be from a digital type noise source 
like a computer, etc. If you move the TV to another room and the 
interference changes, that's probably it.

EM or RFI hell?

"About a mile from my home there are four TV (channels 2, 4, 9 and 14) and
 several broadcast FM transmitters, all working with powers in the 100+ Kw
 ERP class.

 Radio reception is a nightmare, mostly (I think) because of IM products
 in overloaded front end stages. In most bands there are several regions
 at a spacing of about 100 Khz, each 30 to 40 Khz wide with a harsh buzz
 stronger than anything else."

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

If the buzz is of a frequency like the power line frequency or a
harmonic thereof, then the nearby transmitters may not be the culprit.
Instead, nearby corona on a high voltage power line, a nearby neon sign,
or a nearby light dimmer may be the offender.  Although the noise from
these is usually broad-band, the noise could get concentrated into bands
spaced 100 KHz apart if something resonant around 100 KHz is involved in
the noise production.

I would try temporarily turning off all fluorescent lights, neon signs,
lights with dimmers, etc. and asking your neighbors to do the same to see
if any of these is the offender.  I have often found light dimmers to be
major RF noise sources.

Possibly, an RF noise filter for the AC power for your receiver may help
things.  If you isolate a single offending appliance, it may help to plug
it into an RF noise filter.  If you use any filters with either the
offending appliance or the receiver, try all combinations of plug reversal
to see what works best.  Both leads of any offending appliance may not
equally spew noise, and both lines in the filter may not equally block
noise.  Both lines of the receiver's power cord may not equally bring
noise into the receiver, if this is the route the noise takes.

Chapter 27) Audio Problems

  27.1) Picture fine, no audio

First check that any muting control is not activated.  This might be
a button on the remote or set itself.  If you have a headphone jack, it
may have dirty contacts as plugging in a headphone usually mutes
the speaker.

If the set is mono or only one channel of a stereo set is out, then
check for bad connections to the loudspeaker.  Test the loudspeaker by
disconnecting one of the wires (with the power off!) and measuring its
resistance with an ohmmeter (it should be less than 100 ohms - probably
less than 8 ohms).  Or momentarily touch a 1.5 volt battery to the speaker
terminals - you should get a click or pop from the speaker.

Next, trace back from the speaker output terminals to the circuit board
and look for bad solder connections or a loose or dirty connector.

If these tests do not reveal anything, you probably need a scope (or
audio signal tracer) and schematic.   Or at least the part number off of
the chip.  Is the final amp a chip also or just a transistor?  Have you
tested the transistor?  If there is little or no buzz from the speaker,
that would indicate a problem fairly near the output.  If the tuner/if were
bad, I would expect some noise/humm pickup from the low level audio stages.
Get the part number off of the chip. If it is in a socket, check the
contacts for corrosion or looseness.

  27.2) Weak or distorted audio

Assuming you are not attempting to play it at ear shattering levels,
this may be due to an alignment problem in the IF/audio demodulator,
a bad audio IC or other circuitry, bad connection, or a defective speaker.

If your TV has an earphone or audio line out jack, try this to see if it
is clear.  If so, then your problem is in the final audio amp or speaker(s).

If only one channel of a stereo TV is affected, it is almost certainly the
audio amp or speaker for that channel.  Interchange connection to the two
speakers temporarily and see if the problem moves.

If the problem is at all intermittent - try gently whacking the TV - then
it is likely a bad connection - either a cold solder joint or a dirty
or tired IC socket.

The audio amplifiers in newer TVs are almost always ICs and replacements
are usually readily available.  If the IC is in a socket, remove the IC,
clean the pins and socket contacts and reinstall it.  Sometimes, the contacts
on old socket lose their springiness and do not provide solid connections.
Such a socket will need to be replaced.

If the set uses discrete transistors, it s also possible for one of these
to become noisy.

If your TV is fairly old - 10 years or so - this may be an alignment problem
requiring tweaking of a coil in the sound IF.  See your service manual.
It may be possible to have similar problems with newer TVs but this is
relatively rare.

  27.3) Buzzing TV

Do you actually mean buzz - low frequency as in 60 Hz?  Or, do you really mean
high pitched whine.  If the latter, see the section: "High pitched whine or squeal from TV with no other symptoms".  Or, it may be a combination of both
effects.  Is the buzz through the speaker or from the inside of the set?

* If it is the speaker, then it is a problem with the audio circuitry.  This
  could be a design issue - very common or an actual fault (if it wasn't there
  before).  It could also be interference caused by fluorescent lights or
  appliances like vacuum cleaners with universal motors or body massagers with
  vibrator interrupters (which generate sparks).

  Where the source of the problem cannot be located or eliminated, consider
  using a (HiFi) VCR for the tuner with an external stereo amplifier and the
  disable the internal speaker.

* There is a slight possibility that the AC power in your house has some
  harmonic content - the waveform is not sinusoidal.  This might be the case
  if you try to run on the same circuit as an active dimmer or something else
  with thyristor control.  Proximity to heavy industry could also cause this.

  Relocating the offending device to another branch circuit may help.  You
  could also try a line conditioner (not just surge suppressor) which includes
  filtering.  Or, use a HiFi VCR as your audio source (see above).  Else,
  petition to have that metal foundry move out of the neighborhood :-).

* However, a buzzing that only occurs when the picture has sharply defined
  text or graphics, may be an overload problem at the source - some TVs
  simply handle it better than others.

  If it is a fault in the TV, an adjustment to the tuner or IF may be needed.

  (From: Paul Weber (webpa@aol.com)).

  Not to disparage proponents of the evil demon theory, but the phenomenon is
  more commonly known as "sync buzz".  It is caused by poor performance in the
  TV's audio circuitry.  It can usually be fixed by (1) reducing the signal
  strength and/or (2) tweaking the sound IF coil.  Unfortunately, some of the
  latest TV receivers have no sound IF coil to adjust.  If your TV has a sound
  IF coil, it can be done by ear, if you don't care about sound quality.
  However,I'd recommend taking it so a competent shop and describing the
  symptoms.  Use the term "sync buzz in the audio," and they'll know what you
  mean.  Be advised that it can't be cured in some TVs due to poor design.

* If it is from inside the set (and not from the speaker), it is in the
  deflection (probably vertical) or power supply.  Either of these can vary
  in severity with picture content due to the differing current requirements
  based on brightness.  It could be a power supply transformer, deflection
  yoke, or other magnetic component.  Even ferrite beads have been caught
  buzzing when no one was looking :-).  Any of these parts could vibrate if
  not anchored securely or as they loosen up with age.

  Some hot-melt glue, RTV silicone, or even a strategically wedged toothpick
  may help.  A new part may or may not quiet it down - the replacement could
  be worse!

  See the section: "Reducing/eliminating yoke noise".

* Some TVs are simply poorly designed.  You cannot infer the severity of this
  annoyance from any specifications available to the consumer.  It is strictly
  a design (e.g. cost) issue.  The size of the TV is not a strong indicator of
  the severity of the problem but there will be some relationship as the power
  levels are higher for larger sets.  The best you can do is audition various
  TVs very carefully to find one that you are satisfied with.

BTW, when I got my new super-duper RCA Colortrak in 1980, it had a similar
annoying buzz - even had a repair guy out who behaved as though this was to
be expected.  I did get used to it and am not even aware of it today - and
still use that set.

Additional comments:

(From: Karen (kclark9835@aol.com)).

Also for some audio buzz problems especially in the older units don't overlook
the possibility of a misaligned trap. or a touch-up of the sound discriminator
may prove helpful.

(From: Alan (algba@ix.netcom.com)).

If the buzz is coming from the speaker suspect a bad saw filter in the if
circuit (very common).

If it is coming from elsewhere in the set it could be the flyback transformer,
line input choke, or most common on those sets - the deflection yoke.  I have
repaired many of these yoke by using a wooden shim and some silicone rubber.
In the collar of the yoke just ahead of the lock down clamp, there are some
metal strips under the plastic.  These are magnet that are used for convergence
correction at the top and bottom of the picture.  If you disturb them too much
it will throw off the convergence.

  27.4) High pitched whine or squeal from TV with no other symptoms

First, make sure it is not coming from the loudspeaker itself.  If it is,
then we are looking at an unusual electronic interference problem rather
than simply mechanical vibration.

If it is a new set and think the sounds will drive you insane, returning it
for a refund or replacement may be best alternative.  However, you may get
used to it in time.  I don't know about returning a set to a store that
doesn't take refunds (I won't even ask about that!).

In most cases, this sound, while annoying, does not indicate an impending
failure (at least not to the set - perhaps to your mental health) or signify
anything about the expected reliability of the set though this is not always
the case.  Intermittent or poor connections in the deflection or power supply
subsystems can also result in similar sounds.  However, it is more likely that
some part is just vibrating in response to a high frequency electric current.

There are several parts inside the TV that can potentially make this noise.
These include the horizontal flyback transformer, deflection yoke, other
transformers, even ferrite beads in the horizontal deflection circuits.  In
addition, transformers or chokes in the switching power supply if this is
distinct from the horizontal deflection circuitry.

You have several options before resorting to a 12 pound hammer:

* As much as you would like to dunk the TV in sound deadening insulation,
  this should be avoided as it will interfere with with proper cooling.
  However, the interior of the entertainment center cabinet can be lined with
  a non-flammable sound absorbing material, perhaps acoustic ceiling tiles.
  Hopefully, not a lot of sound energy is coming from the front of the set.

* Move the TV out of a corner if that is where it is located - the corner
  will focus sound energy into the room.

* Anything soft like carpeting, drapes, etc. will do a good job of absorbing
  sound energy in this band.  Here is your justification for purchasing those
  antique Persian rugs you always wanted :-).

If you are desperate and want to check the inside of the set:

* Using appropriate safety precautions, you can try prodding the various
  suspect parts (flyback, deflection yoke, other transformers), even lowly
  ferrite beads, with an insulated tool such as a dry wooden stick.  Listen
  through a cardboard tube to try to localizing the source.  If the sounds
  changes, you know what part to go after.

* Once you have located the guilty party, some careful repositioning, a
  strategically wedged wooden toothpick, or a dab of RTV silicone or hot-melt
  glue may keep it quiet.  Where the yoke is the guilty party, see the
  section: "Reducing/eliminating yoke noise".

* It is possible to coat the flyback transformer, but this is used mostly
  when there a loose core or windings and you are getting not only the
  15,735 Hz horizontal (NTSC) but also various subharmonics of this.   This is
  probably acceptable but may increase the temperature of the flyback.

* A replacement flyback (or whatever part) may cure the problem unless it is a
  design flaw or manufacturing quality problem.  However, the replacement part
  could be noisier.  You really do not want to replace the yoke (aside from the
  cost) as convergence and other service adjustments would need to be
  performed.  Other transformers can be replaced.

Note that the deflection frequency - just over 15 KHz for NTSC and PAL - is
on the border of audible for adults but will likely be loud to younger people
possibly to the point of being terribly annoying - or worse.  If you are
over 40 (men more so than women), you may not be able to hear the fundamental
at all (at least you can look forward to silence in the future!).  So, even
sending the TV back for repair may be hopeless if the technician cannot
hear what you are complaining about!

BTW, if you have a really old tube type TV, the power tubes (damper and
horizontal output) can also whine but these sets are few and far between
these days :-).

  27.5) Reducing/eliminating yoke noise

(From: Terry DeWick (dewickt@esper.com)).

Carefully look under vertical core next to plastic liner, on top and bottom is
a plate called the astigmatism shunt, it has come loose.  Work RTV, epoxy, or
service cement onto it to glue it down and noise should quit.

(From: TVman (tvman@newwave.net)).

I have fixed a total of 27 of these sets with noisy yokes by removing the
yokes and using motor armature spray sealant.

If you carefully mark the EXACT position of everything (yoke, purity magnets),
and slide the yoke off the CRT, then once the yoke has been sealed with motor
armature spray sealant and has dried thoroughly, put the yoke back EXACTLY
where it was, there should be no problems.

The only thing I have had to do was set the purity on one set, but it
was off a little to begin with.

  27.6) Whining when off?

Many TVs actually run their switchmode power supplies even when off to power
the standby stuff like the remote control receiver, real time clock or timer,
and channel memory.  Depending on the design of the regulator, the power supply
may be running at a low chopper frequency due to the light load.  Some people,
dogs, and rodents are then annoyed.  It could also be an indication of a
fault like a bad capacitor or loosened transformer core if this symptom just
developed - your hearing isn't likely improving :-(.

There is so much running nowadays in 'off' electronics!

Chapter 28) Miscellaneous Problems

  28.1) General erratic behavior

You press VOLUME UP and the channel changes or a setup menu appears all by
itself just at the climax of your mystery story.

Before you break out the screwdriver (or 12 pound hammer), cover up the
IR remote sensor.  Some types of electronic ballasted fluorescent lights
may confuse the remote control receiver.  Someone or something may be
sitting on the remote hand unit or it may be defective and continuously
issuing a bad command.  Or, the kids across the street may have nothing
better to do than to drive your TV (and you) nuts with their remote!

There is also a slight chance power line interference (from a light dimmer
or external sources) may result in similar symptoms.  See the section: "Wiring transmitted interference".

Assuming this is not the source of the problem:

Check for bad connections - see if gently whacking the TV makes any
difference or triggers the errant behavior.  Bad connections in the power
supply, system controller, or tuner, may result in this sort of behavior.
See the  section: "TV and Monitor Manufacturing Quality and Cold Solder Joints".  See the sections and separate documents on problems with
RCA/GE/Proscan and Sony TVs if yours is made by one of these companies.

A microcontroller or other electronic problem is also possible.  If the
symptoms only develop after the set warms up, it may be heat related (though
simple bad connections are more likely).  Use 'circuit chiller' or a heat gun
to identify the bad part.

  28.2) Wiring transmitted interference

The power that comes from the wall outlet is supposed to be a nice sinusoid
at 60 Hz (in the U.S.) and it probably is coming out of the power plant.
However, equipment using electric motors (e.g., vacuum cleaners), fluorescent
lamps, lamp dimmers or motor speed controls (shop tools), and other high power
devices, may result in a variety of effects.

While TVs normally include some line filtering, the noise immunity varies.
Therefore, if the waveform is distorted enough, some effects may show up even
on a high quality TV.

Symptoms will usually be one or two areas of noise moving slowly up the screen.

The source is probably local - in your house and probably on the same branch
circuit - but could also be several miles away.

* The rate will be the difference between the power line frequency (60 Hz in
  the U.S.) and the scan rate (59.94 Hz for NTSC).  This results in a drift of
  about 16 seconds for a complete cycle (8 seconds if the inteference is at
  120 Hz).

  - A single bar would indicate interference at the power line frequency.

  - A pair of bars would indicate interference at twice the power line

  Either of these are possible.

* Try to locate the problem device by turning off all suspect equipment to see
  if the problem disappears.

* The best solution is to replace or repair the offending device.  In the
  case of a light dimmer, for example, models are available that do a better
  job of suppressing interference than the typical $3 home center special.
  Appliances are supposed to include adequate noise suppression but this is
  not always the case.

  If the source is in the next county, this option presents some significant
  difficulties :-).

* Plugging the TV into another outlet may isolate it from the offending device
  enough to eliminate or greatly reduce the interference.

* The use of a line filter may help.  A surge suppressor is NOT a line filter.

* Similar symptoms could also be produced by a defective power supply in the
  TV or other fault.  The surest way of eliminating this possibility is to try
  the TV at another location.

  28.3) Jittering or flickering due to problems with AC power

If you have eliminated other possibilities such as electromagnetic
interference from nearby equipment or a faulty video cable or problems
with the video input (e.g., cable or VCR) - then noisy or fluctuating AC
power may be a possibility.  However, most modern TVs usually have well
regulated power supplies so this is less common than it used to be.  Then
again, your TV may just be overly sensitive.  It is also possible that
some fault in its power supply regulator has resulted in it becoming more
sensitive to small power fluctuations that are unavoidable.

One way to determine if the problem is likely to be related to AC power
is to run the TV on clean power in the same location connected to the
same video input.  For example, running it on an Uninterruptible Power Source
(UPS) with the line cord pulled from the wall socket would be an excellent
test.  The output of the UPS's inverter should be free of any power line
noise.  If the TV's image has now settled down: 

1. Large appliances like air conditioners, refrigerator, or washing machines
   on the same circuit might cause significant power dips and spikes as they

   Plugging a table lamp into the same outlet may permit you to see any obvious
   fluctuations in power.  What else is on the same circuit?  Depending on
   how your house or apartment is wired, the same feed from the service panel
   may be supplying power to widely separated areas.

2. For some unfathomable reason, your TV may just be more sensitive to
   something about the power from the circuit in that room.  There may be
   nothing actually wrong, just different.  While unlikely, a light dimmer
   on the same circuit could be producing line-conducted interference.

   If you have a multimeter, you could at least compare the voltages
   between the location where it has problems and the one where it is
   happy.  Perhaps, the TV is sensitive to being on a slightly
   different voltage.  This might only be a problem if some circuitry
   in the the TV is marginal in some respect to begin with, however.

3. There could be a bad connection somewhere on the circuit.  If your house
   has aluminum wiring, this is a definite possibility.

   Try a table lamp since its brightness should fluctuate as well.  This
   should be checked out by a competent electrician as it represents a real
   fire hazard.

An electrician may be able to pinpoint the cause but many do not have
the training or experience to deal with problems of this sort.  Certainly,
if you find any power line fluctuations not accounted for by major
appliances, on the same circuit this should be checked by an electrician.

  28.4) TV blows fuses or trips breakers or worse when A/V connections are made

You have sent the TV for repair and now three times, it blows something
the instant anything is connected to it in your house.  Other A/V equipment
operates fine.

Assuming all the other stuff is plugged into the same outlet asn is 115 VAC
equipment and that thsi happens instantly when the TV is connected:

Next time they bring it back, measure the voltage between the A/V connector
shields and the shields on your cables - I wouldn't be surprised to find some
substantial fraction of 115 VAC between them.  This would mean that there is
an internal short in the TV (their problem - any competent service center will
routinely check for signal-AC ground shorts) resulting in a connection between
the non-isolated AC ground and the signal ground.  When you connect your
equipment, you complete a path which results in a short circuit.  Depending
on the design of the TV and where the fault lies, much more than a simple
fuse may be destroyed.  This is similar to connecting a scope probe ground
to a live chassis TV - see the section: "Safety guidelines".

  28.5) My TV has the shakes

You turn on your TV and 5-10 seconds later, the display is shaking or
vibrating for a second or so.  It used to only occur when first turned on,
but now, the problem occurs 3 times in 30 seconds.   Of course, many
variations on this general theme are possible.

Some possibilities:

1. External interference - did you change anything or move your A/V setup
   recently?  Do you have a computer monitor nearby?

2. Defective circuitry in TV - power supply regulation, deflection,
   or bad internal connections are possible.

3. Defective video cable (unlikely) - wiggle the cables to be see if
   you can induce the problem.

Note that many of the sources of electromagnetic interference that are
problems with computer monitors like transformers and power lines will
not cause noticeable shaking, wiggling, or jiggling on a TV because the
power line and vertical scan are at almost exactly the same frequency
and any such movement would be very slow.

  28.6) TV displays black box with normal picture border

When the set is first turned on, it works fine for about 20-30 seconds, then
the picture goes away - all but about 1 inch of picture all around the outer
edge of the screen.  The square ring of picture that is left, is dim but
otherwise normal.

(The following from: (jack haney) jhaney@pacifier.com))

If this is a newer set, this sounds very much like a "closed 
caption" box for a captioning system not being used in your area.
Newer Mitsubishis do much the same thing.  If the wrong caption type
is selected inadvertantly, all you'll see is a large black box
on screen taking up about all but an inch each way.Try turning off
all closed caption.  The first time I saw this I looked like a damn
fool in front of a customer, took me 30 minutes to figure it out.

  28.7) Advertising overload

"I noted the advertsing programs put in bright several frames of overshooting
 white signals in purpose of attracting attention which I do not want also it
 gets on my nerves sometimes.  *flash*  *flash*  Ughhh!  Is there a way to
 cutoff the "overload" or tone down that?"

(From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)).

Technically, the TV takes care of its own overload protection.  Or at least it
*should*, on some TV's you will certainly observe the line transformer going
into saturation for a while.  Other than that there is not much you can do,
each TV should represent its input signals with as much fidelity as possible.
Change channels?

(I already suggested not watching :-). --- sam).

  28.8) Strange codes appearing on TV screen

"I've seen this sort of thing on a TV I bought a couple of years ago. I
 only see it when Proctor & Gamble ads are on.
 The newer TVs are required to have Closed Caption decoding (CCD). My TV
 has an OFF-ON button for CCD. It also has a button labeled CH1-CH2. When
 pushed in I get the verbal text on the screen like I should. When the
 button is out, I get the funny codes from Proctor & Gamble."

(From: Tim (jollyrgr@mc.net)).

The code you are seeing is Closed Caption 2.  My Zenith has CC 1, 2, 3, 4,
as well as Text 1, 2, 3, and 4.  I have seen CC 1 which is the normal closed
captions.  CC 2 is used for commercial logging/identification.  There should
be a way to completely turn off the captions.  The TV, as you state, has a
switch for turning off the captions and should solve your problem.

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