Pioneer Sa 708 Humming

[secrets]

Dad is trying to repair a Pioneer sa 708 that has a hum through the speakers even with the volume on zero .The hum is still present when the volume is raised as well .He changed the main power caps and no luck still humming . Removed the input rca jacks and still a hum coming out from the speakers and it is not low or really loud it is there even if you play music with the volume up .We cannot seem to find this problem . I would like to know if it is possible the transformer is causing some ground or feedback or could this be a open fuse resistor
or leaking cap . Any info would help fellas . Someone else had the same problem but they did not explain what they did to find and repair this fault .

 

[bberkom]

Does the hum get louder or softer when you increase or decrease the volume or is it always at the same level? Is the hum present with any input selected or just a certain one?

 

[secrets]

It is always the same level no matter where the volume is set .Hum is present without any input just having the speakers connected with no inputs and humming is there kind of loudish

 

[bberkom]

It doesn't sound like a grounding problem to me. If it's in both channels, I'd suspect something in the power supply, perhaps a leaky capacitor. I am guessing that the caps he replaced were C503 and C504 from looking at the schematic. I'd replace any of the other electrolytic caps in the power supply. Looks like there are 6 or 7.

 

[secrets]

I think changing the power supply caps is a must will update soon .

 

[deanweipa]

I think changing the power supply caps is a must will update soon .

Did you have any luck sorting out the humming?

 

[restorer-john]

It's most likely a power supply related issue. Check your regulated supplies for ripple/hum.