Hi There to you all ,
I have a Marantz PM-32 which is giving me problems.
All the supplies seem present ,the tranistor outputs measure ok d.c wise
but doesn't have output audio either chanel .
I have taken the bottom off and it had some dry joints on a couple
of transistors near the bridge rec they are D2037 and B1357 and the
board is discoloured due to heat.
The power LED come on sometime but is intermittent.
It would be good to get a circuit diagram , can anybody help please?
Do you hear a relay click a few seconds after power up?
If there is no relay click, it is likely one of those transistors has failed - they act as regulators to produce +23v and -16v supplies. The protection circuit operates from these supplies, so if one is missing, the amp will remain in protect mode.
Pretty much any decent TO-220 transistor will work in place of the D2037/B1357 devices. TIP31A/TIP32A should replace them adequately. If you can fit heatsinks to them, even better.
Thanks guys ,
I checked the relay and it's not clicking over and the signal goes in but not out.
So the transistors that operates this I suppose have gone faulty.
But finding a D2037 and B1357 is going to be a problem.
CPC is no ,RS no, Farnell is no .
You probably won't be able to get them. They were originally made by Rohm, but seem to be long discontinued.
As I said in my post above, they are only used as regulators, so they aren't critical. The TIP31A/TIP32A will do the same job.
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