Buzz/Hum coming from Marantz amplifier

[Joachim78]

Hello everyone,

I own a PM-7200KI Marantz amplifier which produces an annoying buzz through the speakers and the headphones too.

This interference is present in both channels and does not increase if I turn up the volume. I know the issue is in the amp since I remove all sources and the noise is still there...

So, I guess it is the AC 50Hz noise.I have been investigating a while on the web and it seems it might be due to a ground problem or defective capacitors. I have checked ground connections and they are OK to me.

So, in my amp, I would have to replace the big capacitors (63V / 12000µF) ? It is not very old (10-12 years old), so I find it strange that capacitors might already be defective...

Or any other suggestions?

Thank you very much for your help!

(Rmq: I have tried the amp on other plugs and it did not change anything)

 

[Joachim78]

Electrolytic capacitors have a limited lifestyle especially if they get hot. They are easy to replace and it's a sensible first step.

Chris

This amp always had a tendency to get really hot after some time... I have not used it for several years actually, maybe they dried out?

 

[hg_mike]

So, in my amp, I would have to replace the big capacitors (63V / 12000µF) ? It is not very old (10-12 years old), so I find it strange that capacitors might already be defective...

These days many consumer goods/cars are built with a 7 year design life, so it is not surprising that capacitors may be having issues after a decade.

 

[drummerman]

You can easily measure them if you have a meter but lift/de-solder one leg before you do so.

 

[Vladimir]

Unlikely the big filter caps gave out before smaller ones in the PSU.

 

[George Hincapie]

The exact same problem happened to my Marantz PM54SE. It was 24 years old though...

Google 'The Audio Cellar' and send Kevin Green an e-mail - he'll repair it for you.

 

[drummerman]

Electrolytic capacitors have a limited lifestyle especially if they get hot. They are easy to replace and it's a sensible first step.

Chris

Indeed and it is easy to get better components to replace the stock items, often the cheapest ones available, especially in budget amps (but also expensive ones).

Replace (or have it replaced) with an item rated to work in higher temperatures and with longer rated life span at maximum temperature. They often cost only a few pence more. If they are PSU components which work in tandem or series it pays to replace them too if you plan to keep the item. Saves future trouble.

 

[chebby]

Electrolytic capacitors have a limited lifestyle especially if they get hot. They are easy to replace and it's a sensible first step.

Chris

This amp always had a tendency to get really hot after some time... I have not used it for several years actually, maybe they dried out?

I'd get the whole amp serviced. Not sure an amp like this should get "really hot" unless it's class A (or an A/B amp that's heavily biased towards class A).

Was is like that even when you bought it brand new?

EDIT: Apparently - after 5 seconds googling - it does have a switchable class A mode ...

Clicky

... I can assume you have this mode engaged from your comment about it running really hot.

 

[Vladimir]

Yup. A lot of Marantz and Yamaha integrateds from the 80's and 90's with switchable Class A biasing cooked themselves to EOL. You can't have Class A and small heatsinks inside[/u] the case.

I had a PM-80mkII that turned into an oven when switched to class A, yet the sound wasn't better or different at all.

Drummerman gave a good advice for the replacement caps to be all quality brand high temp resistance ones. 105 degrees minimum.

 

[Covenanter]

Electrolytic capacitors have a limited lifespan especially if they get hot. They are easy to replace and it's a sensible first step.

Chris

 

[Sixtyten]

I had the same thing occur on an 12 month old PM6005. Marantz replaced it with a new one. It did exactly the same thing straight out of the box. After much "umming" and "aahing" from their repair agents, Marantz, first of all denied there was a buzzing noise, before declaring it was supposed to make this noise while listening through headphones. So no, they wouldn't be replacing it. Fortunately, LRG in Belfast recognising how unacceptable this was, stepped up to plate and delivered some excellent customer service, letting me upgrade to an ARCAM A19 instead. This doesn't make a buzzing noise through the headphone socket. So, presumably in Marantz terms, its absence makes the A19 faulty.

Into the bargain, the A19 makes the Marantz PM6005 sound like a childs plaything.