Please help on Mark Levinson No 331 amp repair - diyAudio
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Old 7th May 2013, 10:31 PM   #1
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Default Please help on Mark Levinson No 331 amp repair

Water damaged Mark Levinson 331 found me and I hope I can bring her back to life again. I washed all water marks and junks from water. Luckily, all transformers are OK but dirty water ate up leads of some parts on the power supply/ protection board. I do not have schematic to refer. Missing parts are near 5 volt voltage regulator. If someone can share schematic or just picture of power supply/ protection board around 5 volt voltage regulator, I will really appreciate.
Click the image to open in full size.
Thank You in advance.

Last edited by birdyman; 8th May 2013 at 12:05 AM. Reason: new pics
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Old 8th May 2013, 01:31 PM   #2
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Here are the missing (lost parts) from water corrosion.
VSMB ( power supply board) R100, R102 and R49 and R51.
If any one now values of these or have hi- res pics around front right side and front center of board pics, may I ask you to share with me?

Thanks in Advance
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Old 9th May 2013, 12:18 PM   #3
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I figured out all of values on missing resistors. But I still like to get a copy of schematic if anyone has it. I found extent of water damage is much greater than I thought because the amp was plugged in while under water. All BJT's on VSMB board are dead. Thanks for looking.
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Old 9th May 2013, 12:22 PM   #4
Mooly is offline Mooly  United Kingdom
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I spotted your post earlier. Water damage, and particularly where electrolysis has occurred is hard to put right. The corrosion eats into PCB print too. A starting point is washing a board (maybe with foam cleaner first) and then rinsing and drying.

I've worked on more "liquid damaged" items than you can shake a stick at over the years and its always bad news in severe cases. Problems can keep appearing.
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Old 9th May 2013, 02:05 PM   #5
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If it was completely switched off it would been easy clean off and few repairs. This amp was in stand-by mode and all the bad things happened while electricity is flowing. Any parts with high supply voltage ( 20v DC or higher on this amp) was cooked and PCB was etched. Luckily ML331 did not have SMD's and high density PCB traces even though they would not release schematics. Wish me luck.
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Old 21st July 2013, 03:04 PM   #6
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Dear Birdyman,

The value of the resistors you ask for, are: R49=1K/0.25W; R51=0.715K/0.25W; R100 and R102=10 ohm/5W
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