Beomaster 3000-2: Mains hum on right channel only.

5 replies
J(
Offline
jamesymurray (archived2)
Bronze
Posted September 17, 2012 at 21:26 GMT
#2194930
Hello All,

I'm a newbie here.
I've currently got a Beomaster 3000-2 amp (with a set of Beovox 3800's and a Beogram 2202)

I've had the amp for a while now, but in recent years has been unused and stored away.

As long as I have had it, there has always been 50hz hum on the right channel only. It's present on both loudspeaker outputs, and the volume of the hum doesn't change with the volume of the amplifier (it's stays constantly at a low level).
It's present regardless of the input selected, so it seems it could be introduced much further along the signal path.

I'm planning to get the lid off over the next few weeks, but was wondering if any of you knowledgable folk out there might have and ideas/hints as to where I should be looking.
Possibly a failed electrolytic?

All the best,

James
D(
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dmacri (archived2)
Bronze
Posted September 18, 2012 at 14:07 GMT
#2194931
If it's always the same level, it's not the amplifier power supply or the main filter caps. So this is being introduced after the amplifier circuits. I assume the hum goes away when the power is shut off, so it's not being injected on the speaker wires due to inductive coupling. I know, not very helpful, but sometimes it's good to eliminate what you can and see what remains, no matter how unlikely...
DI
Offline
Dillen
BronzeModeratorFounder
Posted September 18, 2012 at 15:21 GMT
#2194932

First thing would be to replace the rectifier in the corner of the tuner board.

Martin

J(
Offline
jamesymurray (archived2)
Bronze
Posted October 10, 2012 at 00:53 GMT
#2194933

Thanks for all the suggestions.

Well after a long time I finally had a chance to open the lid. Luckily the original schematic was still contained within the envelope which made tracing the fault a lot easier. Narrowed it down to a popped 47u cap just past the 'lo filter' switch. Replaced that which has cured my hum.

 

 

 

 

R(
Offline
Robob204 (archived2)
Bronze
Posted October 10, 2012 at 01:38 GMT
#2194934

Noticed after reply you've cured the problem ...

b

P.S. I've restored one and sold just few weeks ago - therefore would suggest you pay attention to circuit area of switches and  speakers, Low&High in particular. Also remember there was other thread regarding to incorrect plug wiring (reversed neutral) - but it'll be to late for that - well done

 

jamesymurray wrote:
Hello All, I'm a newbie here. I've currently got a Beomaster 3000-2 amp (with a set of Beovox 3800's and a Beogram 2202) I've had the amp for a while now, but in recent years has been unused and stored away. As long as I have had it, there has always been 50hz hum on the right channel only. It's present on both loudspeaker outputs, and the volume of the hum doesn't change with the volume of the amplifier (it's stays constantly at a low level). It's present regardless of the input selected, so it seems it could be introduced much further along the signal path. I'm planning to get the lid off over the next few weeks, but was wondering if any of you knowledgable folk out there might have and ideas/hints as to where I should be looking. Possibly a failed electrolytic? All the best, James

 

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