Question about Toshiba receiver SA-7100

[Perry]

Hi all - I have a real nice late 70s era Toshiba receiver that has a
problem.

It started out with a noisy right channel, sort of a crackling sound every
so often (all inputs and thru the headphones as well). I took the cover off
and tapped the output transistors with a pen, and discovered that it made
the sound worse and then eventually the sound went away.

The unit worked fine for about a week, then it made a large POP and now it
has no output (in either channel). In fact, it never really comes on all
the way. What I mean by that is, the "click" you usually hear after a few
seconds when turning it on never happens now. I checked all the fuses
inside by the way. Everything lights up as usual, so it appears to be
getting power.

Is it likely the transistors finally shorted or otherwise gave up?

Any ideas are appreciated. I'd like to get it working again, I love the
sound of this unit. Thanks.

Perry

 

[Nigel]

Perry <see@below.com> wrote in
news:Xns94A0D238B558Danother@216.196.105.138:

Hi all - I have a real nice late 70s era Toshiba receiver that has a
problem.

It started out with a noisy right channel, sort of a crackling sound
every so often (all inputs and thru the headphones as well). I took
the cover off and tapped the output transistors with a pen, and
discovered that it made the sound worse and then eventually the sound
went away.

The unit worked fine for about a week, then it made a large POP and
now it has no output (in either channel). In fact, it never really
comes on all the way. What I mean by that is, the "click" you usually
hear after a few seconds when turning it on never happens now. I
checked all the fuses inside by the way. Everything lights up as
usual, so it appears to be getting power.

Is it likely the transistors finally shorted or otherwise gave up?

Any ideas are appreciated. I'd like to get it working again, I love
the sound of this unit. Thanks.

Perry

It sounds as if you had some dry joints in the output stage. Tapping the
transistors didn't help one bit, and now it appears that the protection
relay is keeping the output stage turned off to protect the speakers.

You'll need to check for obvious DJs first, then decide whether you've
shagged the output stage.