Re: Sansui 7070 Power Amp Question

Hi David,
Thanks for your help. I checked this voltage and it appears to be OK
reading +43v. The neg. side also reads -43v. (Both occasionally measure
around 42v.)
Am I correct in my assumption that with the speaker protection relay
de-energized the voltage at pins 10,11 and 22,23 of the F-2624 board
should be zero and not -42?

Thanks,
Joe

David Farber wrote:
> "2Czech" <jhuser@xxxxxxxx> wrote in message
> news:1131396341.539726.176130@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > 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.
> >
>
> Check pins 5, 6, 27, and 28 of the driver board, (F-2624). They should be
> +44 volts. The source of this voltage is TR01 in the power supply (F-2625).
>
> Good luck.
>
> --
> David Farber
> David Farber's Service Center
> L.A., CA

.

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