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marshall 3210 lead Mosfet troubleshooting

Started by Jdomi, June 20, 2022, 02:23:56 AM

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Jdomi

Hi,
I am looking for advices on troubleshooting a Marshall 3210lead Mosfet.
The problem is this: adjusting the bass in "normal" mode has almost no effect.
Everything else works fine. I found the diagram on the web but I don't see what element could cause this defect, in particular around the bass potentiometer. The potentiometer it self or maybe a capacitor?
Has anyone already  seen this problem or have a clue?

Thanks in advance.
(I am french and my English level is not so good, so thanks google translator!)

phatt

Most likely the pot has failed, you might need to replace it.
The wiper which is the center pin can grind away the carbon track or just get dirty and looses contact with the track.
Also look for hairline solder cracks around the pins on the PCB.
You could try circuit cleaner spray into the pot but a new pot might be cheaper than the can of spray. :-X 
Phil.

Jdomi

Okay thanks for the advice, I will try to find and replace the pot, taking also a close look to the PCB solders.

Jdomi