Sony PVM-9044 composite audio not working

[belzrebuth]

Hi,
I've got a weird issue with a Sony PVM 9044 that outputs no audio from either Line A or Line B composite inputs.
RGB audio input works fine..
IC402 audio switch is used for both RGB and Composite audio inputs.
I think that is unlikely for 2/3 of this chip to fail, so kind of stuck on what might be the fault here.
Any ideas would be welcome!
I attached part of the audio schematic, the full schematic is located here:
https://ia600604.us.archive.org/28/items/sony_PVM-9041QM_9044QM_Service_Manual/PVM-9041QM_9044QM_Service_Manual.pdf

[wasedadoc]

The A and B inputs first go to a changeover switch in the IC. Then a second changeover switch selects that output or RGB audio input. That second switch is controlled by the voltage on pin 4. Is that voltage changing?

It only needs half the chip to fail, not two thirds.

[belzrebuth]

Yeah half you are right.! I saw the audio reaching the inputs but I didn't check the switch signal. Will report back..