Pioneer SA-8100 DC Offset & Protection Question

[dbxdx5]

I'm trying to track down some high DC in the preamp section of an SA-8100. When I have the pre and amp sections coupled, the protection relay trips intermittently. When they're separated, the relay is quiet.

Right now, I'm measuring approximately 1.1V and 0.700V DC at pins 11 and 6 (the outputs) respectively of the filter amp board. There's no DC at pins 4 and 13 (the inputs). I've replaced the four light blue Sanyo caps on the switch board (AWS-035), as well as the 10uF/16V caps on the filter board. I'm thinking the source of the DC is on the filter amp board, though the only suspects would be the 330uF and 1uF caps or the two 2SC1313s. Or could the DC be getting into the filter board from somewhere that I'm overlooking?

 

[zebulon1]

I would rebuild the pre boards. New caps and transistors.
More than likely it’s the transistors.

 

[dbxdx5]

Yes, no doubt that would solve it. But I'd rather pinpoint the specific culprit first.

 

[zebulon1]

Yes, no doubt that would solve it. But I'd rather pinpoint the specific culprit first.

Make a lesson out of it. Excellent idea.
Sometimes I’m too interested in getting to the end and not enjoying the journey.

 

[QSilver]

If you have a scope, that will really help you pin point the culprit.

 

[dbxdx5]

Ok, so things are better but still not completely sorted with the protection. The DC offset is now stable, however, the relay is still opening intermittently. In measuring voltages on the AWM-027D board that's in this unit, I'm seeing -4.40V at the negative side of C5, rather than the expected -2.65V. That seems to be too significant of a difference. The voltage at pin 16 is also a little low, though I'm not sure that's enough to merit concern. All transistors on this board have been replaced, as well as every cap except for C8 (need to order). Thoughts on what would cause the voltage at C5 to be raised?

Pin 17: 7.55VAC
Pin 16: 33.9V
Pin 6: -12.66V