Notes On The Troubleshooting And Repair Of Television Sets


  28.9) Releasing 'demo' mode

You really want to watch CNN but the TV insists on promoting itself:

* For Fisher TVs:

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

  Hold down the menu key on the remote for 8 seconds to switch it out of that
  mode or back in again.

* For Magnavox TVs:

  (From: L. Tankersley (boat39@mail.idt.net)).

  Try pressing both volume control buttons on the TV at the same time and
  releasing. The demo mode should go off and the set turn off by itself.
  Turn the set back on and it should be back to normal.

* For Sanyo TVs:

  (From: Bill A. (Lucy27@ix.netcom.com)).

  Try pressing the "menu" button on the unit and keep it depressed for about
  15 to 20 seconds.  This should release the demo mode.

  28.10) TV was rained on

Was the set plugged in when the leak started?  Any piece of equipment with
remote power-on capability has some portions live at all times when plugged
in and so there may have been damage due to short circuits etc.  Substantial
damage could be done due to short circuits.

Otherwise, you may just need to give it more time to dry out.  I have
had devices with keypads getting wet that required more than a week but
then were fine.   There are all kinds of places for water to be trapped and
take a long time to evaporate.

If the set got wet while unplugged (in a leaky attic or wet basement), for
example, or it has a pull or click knob on/off switch, then give it time
to dry out - completely.  Assuming all visible water is drained, a week
represents a minimum safe time to wait.  Don't rush it.

Generally, some moisture will not do any permanent damage unless the
set was on in which case you will simply have to troubleshoot it the
old-fashioned way - one problem at a time.

  28.11) TV was dropped

You have probably seen the TV advertisements - I don't recall what they
were for - where a late model TV is dropped out a many story window
on a bunjie cord to rebound once undamaged and without hitting a baby in
a stroller but then smash to smithereens on the sidewalk once the stroller
had moved.  Needless to say, this is generally not a recommended way to
treat a TV set!

However, mishaps do happen.

Assuming it survived mostly intact - the CRT didn't implode, you could still
have a variety of problems.  Immediately unplug the set!

If you take it in for service, the estimate you get may make the national debt
look like pocket change in comparison.  Attempting to repair anything that has
been dropped is a very uncertain challenge - and since time is money for a
professional, spending an unknown amount of time on a single repair is very
risky.  There is no harm is getting an estimate (though many shops charge for
just agreeing that what you are holding was once - say - a TV, or was it a

This doesn't mean you should not tackle it yourself.  There may be
nothing wrong or very minor problems that can easily be remedied.  The
following are likely possibilities:

1. Cracked circuit boards.  These can be repaired since TVs usually have
   fairly wide open single or two sided boards.

2. Broken circuit components.  These will need to be replaced.

3. Broken solder connections particularly to large heavy components
   on single sided boards.  Reflow the solder.  If the trace is cracked
   or lifted, repair as in (1).

4. Broken mounting brackets.  These are usually made of cheap plastic
   and often don't survive very well.  Be creative.  Obtaining an
   exact replacement is probably not worth the trouble and expense.

5. Components knocked out of line on the CRT envelope or neck  - deflection
   yoke, purity magnets, convergence magnets and coils, geometry correction
   magnets.  These will need to be reattached and/or realigned.  Some CRTs use
   little magnets glued to the funnel portion of the CRT envelope.  If any
   of these have come loose, it could be quite a treat to figure out where
   they went and in what orientation.

6. Internal damage to the CRT - popped or distorted shadow mask, misaligned
   electron guns.  Unfortunately, you will probably have no way of
   identifying these since you cannot see inside the CRT.  They will not
   be apparent until all other faults have been remedied and the TV set
   is completely realigned.  At that point, extremely severe purity or
   convergence problems that do not respond to the normal adjustment
   procedure would be one indication of internal damage.  Give the TV a
   nice funeral.

To test to see if it is a chroma problem - disconnect (or disable) two
of the 3 primary colors with a B/W picture or solid raster displayed.  If
the raster is not now a pure color, you have a CRT or CRT purity adjustment

If you still want to tackle a restoration:

As noted, unplug the TV even if it looks fine.  Until you do a thorough
internal inspection, there is no telling what may have been knocked
out of whack or broken.  Electrical parts may be shorting due to a broken
circuit board or one that has just popped free.  Don't be tempted
to apply power even if there are no obvious signs of damage - turning
it on may blow something due to a shorting circuit board.  If it is a
portable, remove the batteries.

Then, inspect the exterior for cracking, chipping, or dents.  In addition
to identifying cosmetic problems, this will help to locate possible areas to
check for internal damage once the covers are removed.

Next, remove the cover.  Confirm that the main filter capacitors are
fully discharged before touching anything.  Check for mechanical problems
like a bent or deformed brackets, cracked plastic parts, and anything that
may have shifted position or jumped from its mountings.  Inspect for loose
parts or pieces of parts  - save them all as some critical magnets, for
example, are just glued to the CRT and may have popped off.

Carefully straighten any bent metal parts.  Replace parts that were
knocked loose, glue and possibly reinforce cracked or broken plastic.
Plastics, in particular, are troublesome because most glues - even plastic
cement - do not work very well.  Using a splint (medical term) or sistering
(construction term) to reinforce a broken plastic part is often a good
idea.  Use multiple layers of Duco Cement or clear windshield sealer
and screws (sheetmetal or machine screws may be best depending on the
thickness and type of plastic).  Wood glue and Epoxy do not work well
on plastic.  Some brands of superglue, PVC pipe cement, or plastic hobby
cement may work depending on the type of plastic.

Inspect for any broken electronic components - these will need to be replaced.
Check for blown fuses - the initial impact may have shorted something
momentarily which then blew a fuse.

There is always a risk that the initial impact has already fried electronic
parts as a result of a momentary short or from broken circuit traces and
there will still be problems even after repairing the visible damage and/or
replacing the broken components.  This is most likely if the set was actually
on but most modern TVs have some circuitry energized at all times.

Examine the circuit boards for any visible breaks or cracks.  These will
be especially likely at the corners where the stress may have been greatest.
If you find **any** cracks, no matter how small in the circuit board, you
will need to carefully inspect to determine if any circuit traces run
across these cracks.  If they do, then there are certainly breaks in
the circuitry which will need to be repaired.  Circuit boards in consumer
equipment are almost never more than two layers so repair is possible but
if any substantial number of traces are broken, it will take time and patience.
Do not just run over them with solder as this will not last.  Use a fine
tipped low wattage soldering iron and run #22-26 gauge insulated wires
between convenient endpoints - these don't need to be directly on either
side of the break.  Double check each connection after soldering for correct
wiring and that there are no shorts before proceeding to the next.

If the circuit board is beyond hope or you do not feel you would be able
to repair it in finite time, replacements may be available but their cost
is likely to be more than the equipment is worth.  Locating a junk unit of the
same model to cannibalize for parts may be a more realistic option.

Degauss the set as any impact may magnetize the CRT.  Power cycling may
work but a manual degaussing is best.

Once all visible damage has been repaired and broken parts have been replaced,
power it up and see what happens.  Be prepared to pull the plug if there
are serious problems (billowing smoke or fireworks would qualify).

Perform any purity, convergence, or other realignment as needed.

Then proceed to address any remaining problems one at a time.

  28.12) Really cleaning a TV inside and out

(This was written for computer monitors but applies equally well to modern
TV sets.)

(From: Dr. Ludwig Steininger (drsteininger@t-online.de)).

Often I get defective monitors, which are more than 5 years old, and have been 
run in offices for 8 to 10 hours/day. So, their case and pcbs usually are very
dirty and dusty.

What do I do (it's no joke!): After removing the case I carefully put them in
a bath (on a flexible layer) and let them have a intensive shower of pure cold
water (for 1 to 2 minutes).  Additionally, the case is cleaned with soap or a
detergent containing liquid (being careful, not to spill to much of it onto
the PCBs). After rinsing with fresh clear water, dust and other kinds of dirt
are removed and the monitors look new again.  Then I allow all drops of water
to run off. This can effectively be supported by turning the monitor on
another side from time to time (duration: approximately 1 hour). Before
turning on AC again, I let the wet monitor dry in ambient air for about 2 days
(in the  sunshine this can be finished in 1 day only).

This procedure has been applied for many monitors. I've never had any bad 
experiences (it's very important to wait, until the pcbs are really dry!). 
Considering this experience, I just can't imagine, that it might not be 
possible, to "save" a TV set or computer monitor, which has been drowned or 
some liquid has been spilled, and AC has been plugged off ASAP (although I've 
never had such a case). I think, that in such a case, it's important to have a
rapid shower in order to prevent corrosion and deposits.

By the way: I know a German company, which uses water from cleaning PCBs of 
computer hardware for cleaning them after being contaminated by smoke from 
a fire.

So, in case of spillage, one has nothing to loose. Just try to shower your 
monitor or TV set!

  28.13) Setup menus will not go away or hieroglyphics on screen

Both these problems could be caused by a faulty microcontroller or
its associated circuitry.  However, bad connections in the vicinity
of the controller logic could also be at fault.

Unless you see something obvious, you will need schematics.

  28.14) Setup adjustments lost - TV service codes

Many modern TVs have RAM, somewhat like the CMOS SETUP memory in your PC,
that store all factory adjustments.  When power is lost, there is power
surge, lightning strike nearby, nuclear detonation or EMP, it may
have put bad information into the ram and thrown it out of adjustment.  There
is a way to get into the service mode (depress and hold a secret button
down and turn set on, special combination of buttons on the remote, etc.)
and then use the remote to reinitialize and adjust the problems out.


Try not to make any unnecessary changes and document every change you make!!!
That way you can go back if you do anything wrong (hopefully).  However, some
changes - even if nothing fails - will result in an unviewable picture thus
making it extremely difficult to see what you are doing.

The Sams' Photofact manual describes this process - you may be able to get
Photofacts from a local library, or you can buy them from Radio Shack or
a place like MCM Electronics or an electronics distributor.

Some examples follow.  You would need to check the service information for
your specific model to be sure.  However, trying the procedures described
below probably will not hurt.  The TV will just ignore you if it doesn't
like your codes!

* Ferguson/Thomson Technology T49F television (TX91 chassis and probably
  others as well).

  (From: Peter Radlberger (peter.radlberger@blackbox.at)).

  - Unplug SCART cable.

  - Switch to Standby, then switch mains off.

  - Hold blue button on remote, power up.

  - Repress blue button, service screen appears.

  - Select function with blue, adjust with Vol+/-, store new value with
    highlighted Memo and Vol+.  Restore jumps to original value, ROM are
    production defaults.

  - Leave with Standby.

* Some JVC models (JA chassis):

  (From: Roger Dowling (rogerd@globalnet.co.uk)).

  Press the DISPLAY key and the CINEMA/GAME key of the remote control

* Some JVC models:

  (From: Andy Cuffe (baltimora@psu.edu)).

  I have used this on JVCs from 1995:

  - Set the clock to 3:21 AM.

  - Start the clock as you normally would but press MUTE while "Thank you" is

  - Press menu up or down just after MUTE.

  - Use up/down to select options and left/right to adjust.  The settings are
    automatically saved when you exit.

* Some Magnavox models: Enter 062596 then MENU.  The channels will change but
  when MENU is pressed, the TV will enter the service menu.

  (From: Gscivi (gscivi@aol.com)).

  Hit MENU on the remote, while the menu is still up press the numbers 061596
  or 061597.  One of these will bring up the service menu. Now, your right/left
  arrows on remote will switch between the numbers across the bottom of the
  screen, highlight the number set right after the 'setup or service' option.
  The arrow up/down will change to the next service position.

* Some Mitsubishi models: Use your remote and press MENU then 2357 use VIDEO
  to select service menu and ADJUST to set values.

* Some Nokia (ITT) models:

  (From: Stefan Huebner (Stefan.Huebner@rookie.antar.com)).

  Press mono/stereo - Channel C - Hypersonic  within 1 second,  The display
  now shows SE.  Leave the service mode with the standby button.

* Nokia model 6363:

  (From: Ian Abel G3ZHI (bert@skypilot.demon.co.uk)).

  Nokia model 6363 (and probably other late model TVs) - On the remote press
  -/-- then menu then TV all within 1 second.  When in setup mode you use
  channel up or down buttons on the TV set to change to whatever you need to
  set up.  Adjustments are made with volume + and - buttons on the remote
  control.  My advice is to make a note of all the settings before making
  changes then you can always go back to them.

* Some Panasonic models: A very detailed document on Panasonic Service(man)
  mode for some models in the GL10C family (may apply to others as well) is
  provided at:

  - http://www.colpetzer.com/calanan/Panasonic/

  Includes entering/saving/leaving, register contents and range, etc.

* Panasonic TX-W28R3 (and similar models):

  (From: Arpad Kothai (arpadk@EUnet.yu)).

  The remote control is used for entering and storing adjustments, with the
  exception of cut-off adjustments which must always be done prior to service
  adjustment. Perform adjustments in accordance with screen display. The
  display on the screen also specifies the CCU variants as well as the
  approximate setting values. The adjustment sequence for the service mode is
  indicated below.

  1. Set the Bass to maximum position, set the Treble to minimum position,
     press the Reveal on the remote control and at the same time press the
     Volume on the customer controls at the front of the TV, this will place
     the TV into the Service mode.

  2. Press the RED/GREEN buttons to step down  / up through the functions.

  3. Press the YELLOW/BLUE buttons to alter the function values.

  4. Press the STORE button on the preset panel after each adjustment has been
     made to store the required values.

  5. To exit the Service Mode press the Normalization button.

* Some RCA models: The codes can be found pasted to the inside of the
  back cover.  To get into the SETUP MENU, "Press and hold MENU, hit POWER and
  then VOL+.  DO NOT set H Freq too low or you will wipe the EEPROM.  Bummer.
  For more information, see the document: "RCA/GE TV (CTC175/176/177) Solder
  Connection and EEPROM Problems"

* Some Samsung models:

  (From: Livio Belac (lbelac@efpu.hr)).

    ON (PWR ON).


  Perform adjustments with VOL +/-

  Select between adjustments with CH +/-

* Various Sony models: Service mode adjustments can be found at:

  - http://www.repairfaq.org/REPAIR/F_SonySet.html.

* Another Sony:

  (From: Trygve Pedersen (trygve-p@netpower.no)).

  To enter service mode turn off power push both + and - buttons on front of
  TV while you powers up you get TT on screen, and then you enter 34 (TT34 on
  screen), press the left arrow twice on remote, and you are in service mode.

* Some Sony UK models: Fast text buttons operate service mode.

* Sony KV-X2571 and similar models:

  (From: Peter & Jolanda Faber (pfaber@worldonline.nl)).

  Switch TV off.  Press and hold two switches (center & right) under front
  panel.  Switch set on with main switch.  Wait a few seconds.  Release two
  switches again.
* Some Toshibas:

  (From: Bill A. (Lucy27@ix.netcom.com)).:

  1. Press the mute button on your remote and release (put unit in mute).

  2. Press and hold mute button on remote.

  3. At the same time while holding mute button on remote, press the menu
     button on the TV itself.

  If done correctly an "s" should show up on the screen to determine that you
  have successfully entered the service mode.

  5. Now, I believe if you press the menu button again on the unit some
     microprocessor data should be showing up on screen i.e. current micro
     part# etc.

  6. Press #9 on remote to enter various modes of operation.  Here is where you
     really need the service manual, too much info to show here.

  Once in Service mode be very careful!!!

* Zenith System 3:

  (From: Raymond Carlsen (rrcc@u.washington.edu) and jollyrgr@mc.net).

  Hold the MENU button down for about 5 seconds... until the currently
  displayed menu disappears.  Then press 9 8 7 6, then ENTER. There are two
  menus in the service mode.  Use the MENU to toggle between them. Press
  SELect until the item you want is highlighted, then the ADJ button (left
  or right) for the submenu or the adjustment. Press SELect for the next item
  and MENU for the alternate menu.  Press ENTer to exit the service mode.

  28.15) Service menu caution

Even changing a parameter which results in the loss of the picture could
require replacing the EEPROM if you cannot get the set to come on and view
the service menu to reset!

However, it may be possible to drive the HOT with an external source
so you can see the menus for setup.

CAUTION: there is some risk.  Should drive the HOT with too low a frequency,
it may blow due to flyback core saturation.  Use a series light bulb to
minimize this possibility.

  28.16) Strange number in upper left corner in Magnavox service mode

"When I put my Magnavox in service mode a number comes up on the top left
 of the screen. I see no description of it in the service manual. Is this
 an hours used timer? Is it actually in hours?"

(From: Mister M. (mister-m@ix.netcom.com) and zapper (zap@mhv.net)).
This is actually a usege timer in hexidecimal. 

Hey, at least it is not binary --- sam :-).

  28.17) TV doesn't work after being in storage

So the TV you carefully stuffed in a corner of the garages is now totally
dead.  You swear it was working perfectly a year ago.

Assuming there was absolutely no action when you turned it on, this has
all the classic symptoms of a bad connection.  These could be cold/cracked
solder joints at large components like transformers, power resistors, or
connectors and connectors that need to be cleaned or reseated.  By 'no action'
I mean not even a tweet, bleep, or crackle from anything.

To narrow it down further, if careful prodding with a well insulated stick
does not induce the set to come on, check the following:

1. Locate the horizontal output transistor.  It will be in a TO3 metal
   (most likely on an older set) or TOP3 plastic package on a heat sink.
   With power off, measure collector to emitter with an ohmmeter - in at least
   one direction it should be fairly high - 1K or more.  Then clip a voltmeter
   on the 250 V DC or higher scale across C-E and plug in and turn on the set.
   Make sure it is well insulated.

   * If the problem is in the low voltage (line) power supply, there will
     be no substantial voltage across C-E.

     You should be able to trace from the power line forward to find the bad
     part though a schematic will help greatly.

   * If the problem is in the startup circuit or horizontal oscillator/driver,
     then there will be something on the order of 100-160 V across C-E.

     In this case, a schematic may be essential.

Note: don't assume that the metal parts of the chassis are ground - they
may be floating at some line potential.

There is also a slight chance that there is a low voltage regulator
in addition to the horizontal output, so don't get them confused.  The
horizontal output transistor will be near the flyback transformer and
yoke connector.

  28.18) Older TVs with multiple intermittent problems

If the set is say, a GE, with a manufacturing date around 1980, it is possible
you have one of those circuit boards best described as bad solder joints
held together with a little copper.  In this case, prodding may get the set 
started.  The circuit boards in these sets were double sided using what
were called 'rivlets' for vias.  The rivlets were relatively massive -
literally little copper rivets - and they were not adequately
heated  during assembly so there were bucketloads of cold solder joints
that showed up during middle age.  I repaired one of these by literally
resoldering top and bottom of every one of the darn things with a high
wattage iron.

  28.19) TV has burning smell

Assuming there are no other symptoms:

If this appears after extended operation - an hour or more - it may
just be a build up of dust, dirt, and grime over the years.  After
understanding the safety info, some careful vacuuming inside may help.
Just don't be tempted to turn any screws or adjustments!

Dust is attracted to the high voltage section in particular - even the
front faceplate of the CRT collects a lot and should be wiped with a damp
cloth from time to time.

If the symptoms develop quickly - in a few minutes or less, then there
could still be a dust problem - a power resistor may be heating a wad of
it but other possibilities need to be considered.

If not dust, then probably in the power supply but realize that TVs don't
have a nice metal case labeled 'power supply'.  It is just a bunch of stuff
scattered around the main board.  Without identifying the part that is
heating, a diagnosis is tough especially if the set really does
work fine otherwise.  However, if a series regulator were faulty and putting
out too much voltage, the set could appear to work properly but in fact
have excessive power dissipation in certain components.  If cleaning the dust
does not solve the problem, you will probably need a schematic to identify
the correct voltages.

  28.20) Static discharge noise and picture tube quality

"I bought a 29" TV a couple of weeks ago and I have noticed that after being
 switched on for > about 15/20 minutes, whenever the picture changes from a
 "light" scene to a darker scene, the set makes a crackling noise. It sounds
 as though there has been a build-up of static and it is being discharged. I
 have never noticed this in a TV before and I was wondering if this is normal
 and acceptable behaviour for a large-screen TV?"

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

It probably is normal.  Whether it is acceptable is a personal matter.   In
some geographic areas no countermeasures are taken at all... 

When the scene changes from bright to dark, the beam current is reduced to
practically zero. As a result, the high voltage rises. (The high voltage
supply has a relatively high internal impedance.) The high voltage is
connected to the inside layer of the picture tube. A voltage change on the
inside will also cause a voltage change on uncovered parts of the outside,
especially on the part of the picture tube that is hidden under the deflection
coils. This causes little sparks between the picture tube surface and the
inside of the deflection coils and this is accompanied by a crackling sound.

On the better picture tubes, a dark "anti-crackle coating" is painted on the
picture tube near the deflection coil.  This is a very high impedance coating,
dark black, much darker than the usual aquadag coating over the rest of the
picture tube. You should be able to see the difference.

If, on the other hand, the outside of the picture tube near the deflection
coil is not coated then you have a problem. Then you will hear strong
crackling also at switch-on and switch-off. Normally you shouldn't see such a
'cheap' picture tube on the European market...

The area of the picture tube around the anode connector is also not coated,
for obvious reasons. Normally that should not cause any significant
sound. Same goes for the front of the screen and neither should the anode
cable crackle.

In a dark room you should be able to see from the tiny blue flashes where the
sound comes from. This is perhaps best observed at switch-on and switch-off
(with a black picture on the screen). Try and keep the back cover mounted !

  28.21) Revival of dead or tired remote control units

There are two types of problems with hand held remote controls: they
have legs of their own and they get abused or forgotten.  I cannot
help you with walking remotes.

Where response is intermittent or the reliable operating distance is
reduced, first check the batteries and battery contacts.  If some buttons
are intermittent or dead, than the most likely cause is dirty or worn
contacts under the rubber buttons or on the circuit board.

If there is no response to any functions by the TV or VCR, verify that any
mode switches are set correctly (on both the remote and the TV or VCR).
Unplug the TV or VCR for 30 seconds (not just power off, unplug).  This
sometimes resets a microcontroller that may have been confused by a
power surge.  Confirm that the remote has not accidentally been set to
an incorrect mode (VCR instead of TV, for example).  If it a universal
type, it may have lost its programming - reset it.  Make sure you are
using the proper remote if have multiple similar models.

Test the remote with an IR detector.  An IR detector card can be purchased
for about $6.  Alternatively, build the circuit at the end of this document.
If the remote is putting out an IR signal, then the remote or the TV or VCR may
have forgotten its settings or the problem may be in the TV or VCR and not
the hand unit.  The following is just a summary - more detailed information
is available in the companion document: "Notes on the Diagnosis and Repair of
Hand Held Remote Controls".

Problems with remote hand units:

All except (1) and (2) require disassembly - there may be a screw or two and
then the case will simply 'crack' in half by gently prying with a knife or
screwdriver.  Look for hidden snap interlocks.

1.  Dead batteries - solution obvious.

2.  Corroded battery contacts,   Thoroughly remove chemical deposits. Clean
    contacts with pencil eraser and/or sandpaper or nailfile.

3.  Broken connections often between battery contacts and circuit board,
    possibly on the circuit board - resolder.

4.  Bad resonator or crystal - replace, but diagnosing this without
    an oscilloscope may be tough.  Broken connections on resonator legs
    are common.

5.  Dirt/spills/gunk preventing keys from operating reliably.  Disassemble
    and wash rubber membrane and circuit board with water and mild detergent
    and/or then alcohol - dry completely.

6.  Worn or corroded contact pads on circuit board.  Clean and then use
    conductive Epoxy or paint or metal foil to restore.

7.  Worn or dirty pads on rubber keypad.  Clean.  If worn, use conductive
    paint or metal foil to restore.

8.  Cracked circuit board - can usually be repaired as these are usually single
    sided with big traces.  Scrape off insulating coating and jumper breaks
    with fine wire and solder.

9.  Bad LED. If IR tester shows no output, remove LED and power it from
    a 9V battery in series with a 500 ohm resistor.  If still no output,
    replace with readily available high power IR LED.  Otherwise, check
    driver circuits.

10. Bad IC - if it is a custom chip, forget it!  Failure of the IC
    is usually quite unlikely.

   (The following is from Duane P Mantick:)

   An awful lot of IR remotes use IC's from the same or similar series. A
   common series comes from NEC and is the uPD1986C which, incidentally is
   called out in the NTE replacements book as an NTE1758. A lot of these
   chips are cheap and not too difficult to find, and are made in
   easy-to-work-with 14 or 16 pin DIP packages. Unless you have no soldering
   or desoldering skills, replacement isn't difficult.

There are a large variety of universal remotes available from $10-$100. For
general TV/VCR/cable use, the $10 variety are fine. However, the preprogrammed
variety will not provide special functions like programming of a TV or VCR.
Don't even think about going to the original manufacturer - they will charge
an arm and a leg (or more). However, places like MCM Electronics do stock a
variety of original remotes - prices range from $9 - $143 (Wow $143, for just
a stupid remote! It doesn't even have high definition sound or anything
exotic). The average price is around $40.

  28.22) Problems with the IR remote receiver

Although the hand unit is most likely to be the cause of any problems
with the remote control, it is also possible for the IR receive module
to fail or for power to it to be missing.  Microcontroller problems as
well can result in similar symptoms.

First confirm that the hand unit is putting out the correct code.  If it
is a programmable type, try re-entering the settings for your TV.  Install
a set of fresh batteries.  Try a different remote if possible.  Use an IR
detector to verify IR emissions (see the section: "Revival of dead or tired remote control units").

The IR receiver is often a self contained module connected to the rest of
the TV's circuitry by 3 wires: Power (+12 V typical), Ground, and Signal Out.

The IR receiver module will be located directly behind the IR window.  Test
by confirming that DC power is present.  A schematic will tell you exactly
what it should be but figure on 6 to 12 V if you do not have one.  If this
is present and you have an oscilloscope, put is on the Signal Out.  You should
see the demodulated data stream corresponding to whatever key is pressed on
the hand unit.  It should be a logic level signal swinging between 0 and
the supply or +5 volts.

If there is no power, then a bad cable connection or blown fusable resistor
may be the cause.  If there is correct power but no signal, a fault internal
to the IR module is likely.  The internal circuitry may be a combination
of special ICs and discrete components.  The Sams'' or service manual may or
may not provide the details.  There may be an adjustment for the carrier
frequency but don't be tempted to touch this unless you have exhasuted
other possibilities - and them mark it first!

If the signal is present, then there may be a problem in the microcontroller
or other logic on the mainboard.  This will require a schematic to proceed

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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]