Faulty amplifier - no sound from one channel

[Joachim78]

Hello everyone,

I have a problem with a Marantz amplifier (PM 7200): no sound is coming from the last channel (actually I can hear a faint sound when I get really close to the speaker). If I turn on the volume, the left starts to work suddenly; sometimes, it starts to work after a while even if I don't turn on the volume.

However, I have noticed that:

- when the left channel is working, the sound level is not as high as the right channel (not a big dfference though):

- the problem seems to appear on the second speakers output only; only the first one, it works fine

I am sure that the issue is the amplifier.

Does anyone can help me?

Thank you very much.

 

[Vladimir]

Sounds like a cold solder joing, dirt in potentiometer, or loose connection, and in worst case scenario a leaky capacitor/transistor. Any of those can be sorted. Start disconnecting and reconnecting all speaker and interconnect cables to make sure they work righ. Swap the speakers to see if the problem follows them or it's still in the amp.

If you are sure the issue is the amp, you need a professional to inspect it and fix it. It could be solved with few squirts with the contact cleaner, could be resoldering few joints, or replacing few cheap transistors or caps. I think the amp is worth repairing.

 

[eggontoast]

It might also be a dirty output relay.

Try swapping your speakers over to the B speaker outputs & see if it's the same.

 

[Joachim78]

Ok thanks, I think I'll bring it to a professional. I hope he won't charge me too much for that....

 

[Joachim78]

It might also be a dirty output relay.

Try swapping your speakers over to the B speaker outputs & see if it's the same.

Actuallly it works fine with the A speakers but not with the B ones, I have already tried this.

Do you know where this relay is located?

 

[GCE]

Did you check the 2 or 4 inner fuses?

 

[Joachim78]

It might also be a dirty output relay.

Try swapping your speakers over to the B speaker outputs & see if it's the same.

I think you were right. I managed to find the defective relay. I sprayed some contact cleaner in it, hope it will work... Otherwise I'll have it replaced.

Thanks for your help