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Marantz 1030 repair - left channel noise

A

artrr

New Member
Hi all, I´m new here. My Marantz 1030 has a loud hum/noise in the left channel, right is ok. The noise is there with volume at 0, I´ve made a little video to demonstrate:

I´ve built a couple of effects pedals, so I know a little about reading schematics and I can solder, but this is completely new to me, so any help, suggestions or resources for diagnosing this would really be appreciated!
 
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Disconnect the left channel pre-out/main-in jumper on the rear panel. Do you still hear the white noise ?
 
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avionic said:
Well so much for easily eliminating pre-amp or power amp...
Click to expand...
It's not too bad if your handy with a soldering iron. Just two shielded wires from the preamp board to the top of the amp board, but ya, hopefully he has the earlier model.
 
So I received a good tip on another forum - because the L channel is very noisy and gained (when I put signal through it, it´s much louder than R), I was told to measure L and R between the preamp and poweramp, where the voltages were pretty similar, and then by the speaker outputs where they were 1.5V R and 25V left. So the problem is probably in the poweramp. Any suggestions?
 
Since you have both amps on one board, and since the input voltages are the same. start testing voltages at transistors on both sides and compare. Start with the input transistors H701 and H702, and work left to right on the schematic. Test ECB voltages and compare sides. But...do it safely. Use minigrabbers to attach to the legs and connect/disconnect with power off. Somewhere along the line, you will probably find a significant difference, and you can focus on that area to find the culprit(s).
 
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