Marshall JMP-1 level control problem - Jemsite
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post #1 of 3 (permalink) Old 09-08-2009, 06:31 PM Thread Starter
Join Date: Jul 2008
Location: Manchester
Posts: 128
Marshall JMP-1 level control problem

help, ive cleaned the output level knob underneath with contact cleaner, its still scratchy and occasional get volume dips, like when you press on it its ok, but its doing my head in, what can i do?

im really experienced at guitar stuff, but im not sure what else to do here
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post #2 of 3 (permalink) Old 09-08-2009, 08:19 PM
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Re: Marshall JMP-1 level control problem

Take it to an amp tech and have the pot replaced, not much else you can do.
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post #3 of 3 (permalink) Old 09-08-2009, 10:56 PM
Join Date: Jul 2002
Location: Kent, UK
Posts: 289
Re: Marshall JMP-1 level control problem

there's a tiny square open notch on the bulb-bass of the pot, you need to aim the contact cleaner into there and spray a tiny amount while rotating the knob, which will mean opening up the casing to get to it. Make sure there's no liquid on the circuits before turning back on. If it's still under warranty (unlikely since they haven't been produced for a while), Marshall would do this, or replace the pot for you if you drop it off at a local Marshall dealer, and get them to deal with the returns number/collection etc.

Scratchy pots are irritating enough, but if the volume dipping leads to the level knob not working at all (still getting signal, but no control via the knob), then a factory reset will do the trick most of the time.

Last edited by DJR; 09-08-2009 at 11:03 PM.
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