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Marantz 140 - Buzz/Rumble/hum issues

L

labatt242

Active Member
Hello there,

In the past, I had issues with the left channel of my Marantz 140. I serviced my Marantz 140 as :

- Changed the big cap for two 15 000uF 63V Mundorf
- Changed all the transistors except the pre driver and drivers on left channel
- Changed two diodes on both channels
- BIAS and DC adjusted on both channels
- Both channels has been recapped last 3 years
- New relay since last 3 years

I moved to a new appartment and now the buzz/rumble/hum is back. My VU metter goes left and right on the left channel when I have the issue. There is no distorsion in the sound, only buzz/rumble/hum.

I tried several things as :

Revers RCA cable of the pre out, issue did not changed side
Volume knobs have no impact of the issue
I have the issue on all sources
The mode knob on the pre amp have no impact
Tried a MP3 player connected directly to the amp, still have the issue.

Yesterday, I realised when I'm playing with the power cable of my turntable, the left channel goes almost silence and playing well. The turntable is grounded to the pre-amp. The issue is intermittent but arrives more often since I moved.

My question, do I'm getting face to a ground loop issue finally? What I need to check? Which additional test I can do?

Many thanks in advance.

Guy
 
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Anybody have thoughts on this?

I will re-test again and re-adjust all the stuffs tonight. Since yesterday, I started to check cracked ground and I suspect the Left potentiometer (one of the lug is loose). I will try to swap the amp board Left to Right/ Right to Left to see if the issue will swap, but first I will try again using another pre-amp.

Thanks,

Guy
 
Hey Guy,

I don't have an answer for you, but if you haven't got it straightened out yet, maybe post this over in the Marantz Forum.

~J
 
jerrycpor said:
Hey Guy,

I don't have an answer for you, but if you haven't got it straightened out yet, maybe post this over in the Marantz Forum.

~J
Click to expand...
Will do. I resolder a ground wire already and I'm actually testing the amp using a smartphone with DAC and so far so good. Will retry with my Marantz 3600 and that will confirm if it's a pre amp issue or not. I'm testing it all the week.

Thank you my friend!

Guy
 
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