Pioneer amp, no gain

Hi, I have a GM4200 which will not raise or lower the input gain when the gain pot is adjusted.

I have cleaned the gain pot, checked for dry solder joints and no change.

I tested the amp with both phono and din input, interestingly when I use a din input the amp plays louder but the audio is distorted unless I turn the source volume down.

Using din input has no affect on the gain pot either?
 
Where does it become distorted in the signal chain? If you don't have the service manual, the attached image should be close enough.
 

Attachments

  • ScanImage50b.jpg
    ScanImage50b.jpg
    614.1 KB · Views: 33