RCA expert help needed -CTC177 chassis

[moonlite]

Hello RCA guys - I'm trying to solve one of the weirdest problems I've
seen in this chassis yet. Your advice is appreciated.

Everything works fine but no audio of any kind. I know you will say do
tuner grounds and replace eeprom....I did all that. In fact I did much
more than that: replaced mute transistor Q1903 (I grounded the Emitter
on the previous one without help), went into SETUP and switched
speakers to ON (they were in OFF position), replaced audio output chip
just in case (chip is getting B+), tried new speakers, pin 29 of micro
is low so I know TV is not in MUTE condition, checked for bad joints
everywhere. I do not have schematic and the only last option is to
replace LA7610. Has anyone ever had this chip cause no audio ? Is it
possible I overlooked one single connection in the tuner which may
cause loss of audio (which I doubt) ? Thank you.

moonlite

 

[[email protected]]

Did you do the eeprom audio alignment? Or the rest of the eeprom
alignment?
Do the A/V inputs get sound? Is the tv set to SAP audio mode?

 

[moonlite]

Thanks for the response. Eeprom audio alignment ? What parameter is
that ? I never heard the eeprom also has a setting for audio alignment.
Please enlighten me as to how this is done. The only thing I know is
that the speakers have to be switched to ON in the SETUP menu and I did
that.In the VIDEO mode there is no audio as well but picture is fine.
No, the TV is not in SAP mode. Thanks again.

moonlite

 

[John-Del]

Yes, the T chip can cause no audio, but there are too many other areas
that sound can be lost in this chassis. The audio leaves and reenters
the chip at least twice from memory (mine . There is an outboard MTS
chip near the jacks IIRC, and that can cause no audio. You should pick
up a SAMs for this chassis as it would be somewhat useful in almost
every 17X and 187 you will likely run across.

John

 

[inti2]

Hello RCA guys - I'm trying to solve one of the weirdest problems I've
seen in this chassis yet. Your advice is appreciated.

Everything works fine but no audio of any kind. I know you will say do
tuner grounds and replace eeprom....I did all that. In fact I did much
more than that: replaced mute transistor Q1903 (I grounded the Emitter
on the previous one without help), went into SETUP and switched
speakers to ON (they were in OFF position), replaced audio output chip
just in case (chip is getting B+), tried new speakers, pin 29 of micro
is low so I know TV is not in MUTE condition, checked for bad joints
everywhere. I do not have schematic and the only last option is to
replace LA7610. Has anyone ever had this chip cause no audio ? Is it
possible I overlooked one single connection in the tuner which may
cause loss of audio (which I doubt) ? Thank you.

Audio is present with SCART or other inputs (not cable) ?

I.

P.S. = Not an RCA expert, !