Low Volume L Channel Sony STR-7055

[CaseyWKC]

Had severe distortion in left channel of a Sony STR-7055, traced it to a bad transistor in the preamp, replaced it, clean sound but the low volume remained.

Confirmed it wasn't an amp issue by flipping the separate switch on the back and using another pre to test. Equal and clean volume from both channels.

Get balanced and clear audio from headphones as well.

I am not the best at tracing audio paths once they leave the board I am on, but I believe I can trace the audio up until I get through the tone/pre-amp board until I get to S7 which is the separate/normal switch on the back of the unit. I did also test the unit in separate with rca jumpers to amp in.

I have deoxed and cleaned all switches multiple times.

Any ideas?

 

[Dave1027]

Which transistor do you replace?

 

[CaseyWKC]

Which transistor do you replace?

Was Q602 or Q652, wound up replacing both (as in - in each channel)

I also replaced the surrounding 3.3uF caps as they tested with incredibly high ESR. 30-50ohms+

Update : I still have signal loss before Q602, so it is still within the pre.

 

[Dave1027]

Only low in one channel? Did you deox the volume and balance controls?

 

[CaseyWKC]

Only low in one channel? Did you deox the volume and balance controls?

Yes and yes.

 

[CaseyWKC]

Update:

I traced backwards to C613 coming off the IC and found the drop, replaced it and all is well.

Very obvious oversight on my part.