Electronics > Repair

Repair Denon Amp, Stuck for Diodes.


Freind asked me to fix his 80's Denon PMA-535R. He tried to fix it himself by putting a higher rated fuse so it blew more than just the output transitors. I have sourced all the parts needed apart from the diodes.

I need
2 of  MTZJ27A Zeners (Digikey have them but only in bulk, £70 for loads)
2 of 1ss252 that no longer exist.

Does anyone know what equivalent diodes I can buy in small quantitys?

Digikey was the only one that had all the sanken transitors I needed, so I would prefer the diodes came from them to keep delivery charges down.

Thanks Muchly  ;D

1SS252: 4ns recovery, 90V, 130mA.
1N4148: 4ns recovery, 100V, 200mA.

MTZJ27A: 27V @ 45mA.
BZX85B27: 27V @ 41mA.

Edit - Looks like DigiKey doesn't have the BZX85B27 at all (Mouser has thousands). 1N4750A is not as close a match, but should work.

But did it really blow all these parts...? I'm a bit surprised at these diodes, I don't think they'd be in a part of a circuit that would blow up in this case.

Thanks for the help.
Yup they have gone tit's up, the other channel is a handy place to check as that side is working fine. That had a repair done on the output transitors at some point as the date codes are '93 opposed to '89 on the blown channel. The diodes are back to back on the output bases. Looking at the circuit diagram, not the best, but was free from hifiengine.com, that should be as far back as the damage goes. I can't test any further back as the circuit needs to operate for some of the voltage tests and I can't see anything on the schematic to get damaged any further back. I'm doing it for £40 plus parts (£15), more of a hobby jobby :D


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