wrote in message
s.com...
Sony amp model:TA-AX285,year:1990 (guess),when the external tuner is
plugged in (has special shaped plugs) the +12v shorts out of the 7812
three lead regulator I cannot isolate the problem to either tuner or
amp I checked many components on both units.Anyone have any common
repair tips?.Thanks in advance.

Sidney
E-mail:sidneybek(at)yahoo.com
Dartmouth,Nova Scotia
Canada

If the voltage drops, and the regulator gets hot, but the input voltage to
the regulator remains substantially the same, chances are that the problem
is downstream of the regulator, in the tuner. If the voltage drops and the
regulator stays cold, and the input voltage remains substantially the same,
then the problem is likely the regulator itself. If the voltage drops, the
regulator remains cold, and the input voltage also drops, then the problem
is likely on the raw supply to the regulator, possibly an open circuit
bridge diode, or a bad smoothing cap.

This is a bit of a generalisation, and needs to be tempered with experience,
but should at least get you on the right track.

Arfa