Marantz SR7500 Buzz/hum

[moosefuel]

Hi everyone, I acquired a Marantz SR7500 for not too expensive, I'm told that they are great sounding amps and have analog circuits for some inputs. Pretty cool.

Once mine turns on, it has a noticeable buzz which increases when I turn the volume knob. It doesn't seem to matter which input I set it to, although the timbre of the buzz changes a little between the different inputs. I have nothing plugged in at the moment, just the speakers. The buzz is present in the headphone output, too.

I'm not too bad with a soldering iron, so I opened up the amp. I can identify the different boards somewhat, but I don't really have any idea which is causing the buzz or what to do about it. I don't see any obviously bad capacitors, and I don't want to just start messing with stuff without any idea of what's causing it. Has anyone solved a similar problem? What should I try?

Yes I've tried plugging it in to another outlet, and another house for that matter.

Thanks!

 

[TLS Guy]

Hi everyone, I acquired a Marantz SR7500 for not too expensive, I'm told that they are great sounding amps and have analog circuits for some inputs. Pretty cool.

Once mine turns on, it has a noticeable buzz which increases when I turn the volume knob. It doesn't seem to matter which input I set it to, although the timbre of the buzz changes a little between the different inputs. I have nothing plugged in at the moment, just the speakers. The buzz is present in the headphone output, too.

I'm not too bad with a soldering iron, so I opened up the amp. I can identify the different boards somewhat, but I don't really have any idea which is causing the buzz or what to do about it. I don't see any obviously bad capacitors, and I don't want to just start messing with stuff without any idea of what's causing it. Has anyone solved a similar problem? What should I try?

Yes I've tried plugging it in to another outlet, and another house for that matter.

Thanks!

You have bought a dud most likely. If it hums with only speakers and AC connected the unit is likely a recycling job. I just had and AVP do exactly that and then it had a spectacular failure that could have done a lot of damage. You are not going to service that receiver. Components are now mounted by robot surface with hot air soldering.

That is a 20 year old receiver and so there will be no parts. My AVP was only five years old, but Marantz had no parts available so it was marked for death.

Buying an AVR that old was very unwise.

 

[moosefuel]

Buying an AVR that old was very unwise.

It's too bad they don't make these to last. I have other computers/car/etc. which are 30+ years old and still work fine. Granted, I've done maintenance over the years.

It's not the worst decision I've ever made, but if I can't get any better answers, I think you're right, it's off to the recycler.

 

[j_garcia]

7500 is semi-old, but was a good unit. I had m 8300 for over 10 years before it started to have some minor issues, but it still worked. I have the same AVP currently that TLS had before, and the warranty is up soon, so I could be looking before long also.

 

[TLS Guy]

It's too bad they don't make these to last. I have other computers/car/etc. which are 30+ years old and still work fine. Granted, I've done maintenance over the years.

It's not the worst decision I've ever made, but if I can't get any better answers, I think you're right, it's off to the recycler.

I think the biggest issue is the huge part count, which increases the risk of failure. These units rise in complexity year by year. They use standard components. If they used auto grade, let alone aircraft grade the costs would go through the roof. I dio have two AVPS in daily use that have been in regular use for ten years. I think it is fair to say that it is reasonable to consider these units on borrowed time after 14 to 15 years.

So, it is not like it used to be. I have units up to 60 years old in regular use, and working fine. But these are simpler analog units.

So, I would look for something newer or even new.

 

[Eppie]

The complexity of these AVRs make them very difficult to service. It could be as simple as a cold solder joint somewhere but tracing the noise is the challenge. You need either a very sensitive audio probe or an oscilloscope to trace the audio path backwards. If the buzz increases with the volume control, that indicates that the problem is not in the amp section but in the pre-amp or in the digital processing sections. If you don't have the diagnostic equipment then the members are correct and it is likely destined for recycling.