Re: ?? Old Sony audio power amp , noisy channel

Sometimes freeze-mist used with a pinpoint applicator will help narrow it
down.
You could probably just "shotgun" all the small semi's on that channel at a
reasonable cost.
I have seen dual FET's from Sony's of that vintage cause problems like this.

Mark Z.



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"Sofie" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Peter Mance:
> Most usually the source of static like noise is a leaky bi-polar
> transistor......  a scope or audio tracer will be of great assistance in
> finding the culprit......   also, very briefly touching the soldering iron
> to the device in question can make it more or less noisy if it is
defective.
> Once you have located a suspect you can swap it with the identical
> transistor in the good channel.  Also you should inspect the solder
> connections closely....  look for cracked, cold, or otherwise faulty
joints,
> particularly near and around the high heat producing components such as
low
> ohm resistors, diodes and transistors, power transistors and 3 terminal
> regulators.
> --
> Best Regards,
> Daniel Sofie
> Electronics Supply & Repair
> -------------------------
>
>
> "Peter Mance" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > I've got an old Sony power amp, TAN-7B, that i've had for years.
> > One channel has gone noisy.
> >
> > I'm trying to fix it but having a bit of trouble working out which
> component
> > is causing the problem.
> >
> > Its all discrete, FET's, transistors, diodes, capacitors... All the good
> old
> > fashioned stuff.
> > Disconnecting the driver stages from the power stages has eliminated the
> > power stages.
> >
> > I've swapped the few capacitors with the corresponding ones from the
other
> > (non-noisy) channel, so its not a cap.
> >
> > Which components are most likely to go noisy?
> > Any suggestions for best approach to track such a thing would be
> > appreciated.
> >
> > NB. The power rails are clean. so there arent that many options.
> >
> > Thanks in advance.
> >
> >
>
>