Hi all
Today I picked up an old Marantz integrated amplifier from someone local for £0. I'm keen to get it going and in the process hopefully learn something about audio electronics.
This is the amp:
My starting point is as follows:
- it switches on fine.
- left channel through speaker out is completely silent. Moving balance knob to far right has no effect on the sound. Moving balance knob to far left = silence.
- when listening through the headphone out, both channels are equally loud. However when turning balance knob to the far left, once again I get silence.
Weird right?
Difficult question but realistically, have I got any hope of fixing this economically? I have very little electronics skills but am adept at domestic electricity and soldering.
There is a system 1 and a system 2, the symptoms are the same though both sets of outputs.
Here are a couple more pics...
Some caps and transistors!
Speaker terminals:
(the black wire second from bottom doesn't look too solid, but if this connection was bad it presumably wouldn't explain the headphone output issue?)
Underside of PCB:
Thank you guys for any help you might be able to offer. I hope to be a regular and long-standing member of this fine establishment!
Today I picked up an old Marantz integrated amplifier from someone local for £0. I'm keen to get it going and in the process hopefully learn something about audio electronics.
This is the amp:
My starting point is as follows:
- it switches on fine.
- left channel through speaker out is completely silent. Moving balance knob to far right has no effect on the sound. Moving balance knob to far left = silence.
- when listening through the headphone out, both channels are equally loud. However when turning balance knob to the far left, once again I get silence.
Weird right?
Difficult question but realistically, have I got any hope of fixing this economically? I have very little electronics skills but am adept at domestic electricity and soldering.
There is a system 1 and a system 2, the symptoms are the same though both sets of outputs.
Here are a couple more pics...
Some caps and transistors!
Speaker terminals:
(the black wire second from bottom doesn't look too solid, but if this connection was bad it presumably wouldn't explain the headphone output issue?)
Underside of PCB:
Thank you guys for any help you might be able to offer. I hope to be a regular and long-standing member of this fine establishment!
Welcome to diyAudio 
Well, you stand a fair chance of success but you need to have a circuit/manual to see whats what. Or more specifically, for us to see whats what because we haven't the luxury of seeing the actual unit
The big worry on anything like this are the "model specific parts"... and I'm looking at the sliders, switches and pots. The electronics should be a doddle.
Well, you stand a fair chance of success but you need to have a circuit/manual to see whats what. Or more specifically, for us to see whats what because we haven't the luxury of seeing the actual unit
The big worry on anything like this are the "model specific parts"... and I'm looking at the sliders, switches and pots. The electronics should be a doddle.
Hi!
You can download free Service manual for Marantz PM550 on HiFiEngine, but you must registrated first:
Marantz PM550DC | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
You can download free Service manual for Marantz PM550 on HiFiEngine, but you must registrated first:
Marantz PM550DC | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
With any fault like this you have to start somewhere The best way would be with a scope and signal generator (or test CD etc) and just trace the signal through. That would show any and all problems in literally a couple of minutes.
Without that and you have to be creative.
Most likely causes "from the off" might include faulty/dirty/damaged (as in they have had a bash) controls and switches and also physical damage (cracks etc) to any of the circuit boards these panel mounted controls are connected to.
Beyond that and you need to start by checking each power amp in turn. Inject a signal into the input of each (or use the official engineer method of touching each input with a screwdriver to see if any hum/buzz/noise comes out and whether it is judged similar between channels). If that produces no output then DC voltage checks of the bad channels power amp are next.
The best way would be with a scope and signal generator (or test CD etc) and just trace the signal through. That would show any and all problems in literally a couple of minutes.Without that and you have to be creative.
Most likely causes "from the off" might include faulty/dirty/damaged (as in they have had a bash) controls and switches and also physical damage (cracks etc) to any of the circuit boards these panel mounted controls are connected to.
Beyond that and you need to start by checking each power amp in turn. Inject a signal into the input of each (or use the official engineer
method of touching each input with a screwdriver to see if any hum/buzz/noise comes out and whether it is judged similar between channels). If that produces no output then DC voltage checks of the bad channels power amp are next.
There is some good news, in that if the headphones have output, then so do both amplifiers. The headphones derive their output from the power amplifier outputs, via 330R resistors, R901, 902.
The big questions are; how much output current can the non-working channel deliver and if it is OK, why does the output stop at the headphones? Since both speaker systems give the same result with separate switches S501-1 &2 and the headphones are independently connected, the diagnosis is that the problem lies in the power amplifier itself. Typically, this is because output stage transistors have failed and can't deliver enough current but still admit enough to drive the 'phones. It may also be due to physical damage as Mooly describes but I'm always suspicious of "phones OK-speakers not" as a symptom. It's not an easy repair, sourcing the old replacement parts but is still doable, given the tools, a little cash, lots of coaching and our enthusiastic support.
The big questions are; how much output current can the non-working channel deliver and if it is OK, why does the output stop at the headphones? Since both speaker systems give the same result with separate switches S501-1 &2 and the headphones are independently connected, the diagnosis is that the problem lies in the power amplifier itself. Typically, this is because output stage transistors have failed and can't deliver enough current but still admit enough to drive the 'phones. It may also be due to physical damage as Mooly describes but I'm always suspicious of "phones OK-speakers not" as a symptom. It's not an easy repair, sourcing the old replacement parts but is still doable, given the tools, a little cash, lots of coaching and our enthusiastic support.
hi....i too love the old marantz gear......i have a PM250 - it had a similar kind of issue, and would spike in one channel from time to time then went dead eventually. i found that tightening the potentiometer for the volume control and securing the board behind it actually fixed the problem in mine. i hope this helps you.