Riddled TV Repair Forum

Terry · Guest

This set is in audio mute, sound appears at turn on then goes to mute (not on screen "mute") There is a fix for that but I can't find it in my files. HELP Please.
Terry

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MikeB · Guest

EEPROM stereo alignment data is corrupted. VERY VERY common due to the
tuner
ground and HOT heatsink ground tab problems. Is this your first Thomson
ctc177/187 repair? If it is the Thomson training manual and troubleshooting
guide they put out will be very helpful, order them from Thomson
publications,
some parts distributors also have them, i.e. Excel.

If you really only have half voltage p-p on the SDA something is loading it
down and you need to troubleshoot that failure first.

Gabe · Guest

Terry , probably a corrupted data in your eeprom....
I remember lifting the mute transistor(surface mounted) in some older ctc model .. could be the same issue.

Terry · Guest

Mike, I have done 100's of these chassis'. Some had the muted sound problem
and I did have the data for the fix but I can't find it right now. Changed
the eeprom the original wouldn't let the set turn on. Everything else is
fine but the sound.

JoeB · Guest

Can you write the data to the EEPROM.

I use the PonyProgram to read and write EEPROMS.

Before you touch anything else,
try writing 0x0F to address 0x00

bit 0: 1=speakers enabled 0=disabled
bit 1: 1=tone high 0=normal
bit 2: 1=air 0=cable
bit 3: 1=autocolor enabled 0=disabled
bit 4: 1=closed captioning enabled 0=disabled
bit 5: unused
bit 6: unused
bit 7: unused

Another way is to install an 8 pin socket
plug in a working EEPROM
turn set OFF but do not unplug
put the old IC in and test

Another way is to remove the mute line
to the audio output
but this will allow a "pop"
when turned ON/OFF and possibly channel change.

Joe

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silv · Joined: 07 Jun 2007 Posts: 57

If the advice given by the other people don't work.replace Q1954 tests good,but fails under load,and check U 3201,and remove Q404 from circuit this transistor not needed.