shorted rca to main gnd

Have amplifier which gives big noise to other amplifiers when rca connected to it.
RCA (secondary ground) is shorted to the primary ground.

Not exact amplifier and schematic, but idea is the same. removed r166 and cc29 - still short. Is there some other common point where it can still make a short between these two grounds?
 

Attachments

  • sundown.png
    sundown.png
    515.3 KB · Views: 103
  • rca.png
    rca.png
    65.8 KB · Views: 104
Last edited:
Yes it is out of the heatsink.
I have no info about it - i see that it was repaired before, outputs was changed as well as power supply, but doesnt have any suspicious parts where can see damage, seems like work before was done fine.

Another thing is that there was replaced rail supply capacitors, maybe there is layer on top with secondary ground polygon which is somehow shorted to main gnd?