Sansui 7070 Power Amp Question

I recently acquired a non-working Sansui 7070 Receiver. The main
symptom is the speaker protection circuit is activated all the time.
This appears to be due to the presence of a high DC voltage at the
power amp output. Actually the neg. rail voltage (-42v) is present at
the output of BOTH channels. I checked the output transistors
expecting to find a couple shorted but they all check OK so I'm
thinking the problem is up the chain somewhere in the driver stage. It
seems odd though that the DC is present on both channels suggesting the
same part failed on both channels. Is it reasonable to think that
there may be a power supply problem since it is common to both
channels?

Any help/advice is greatly appreciated.

.

Relevant Pages

  • Re: humming sound from receiver
    ... If you are not experienced in servicing electronic equipment, ... As far as I recall, the power supply on these is common to all channels, ... the hum is affected by the setting of the volume control. ... Any power supply problem ...
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  • Re: humming sound from receiver
    ... If you are not experienced in servicing electronic equipment, ... As far as I recall, the power supply on these is common to all channels, ... the hum is affected by the setting of the volume control. ... Any power supply problem ...
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  • Re: humming sound from receiver
    ... If you are not experienced in servicing electronic equipment, ... As far as I recall, the power supply on these is common to all channels, thus if the hum is on one channel only, it is highly unlikely that it is being caused by the main smoothing caps. ... Any power supply problem will normally not have the symptoms it's causing, affected by the volume setting, and will affect all channels equally. ...
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  • Re: Sansui 7070 Power Amp Question
    ... > This appears to be due to the presence of a high DC voltage at the ... > the output of BOTH channels. ... > there may be a power supply problem since it is common to both ... David Farber ...
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