Marshall volume working in reverse

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Marshall volume working in reverse

Postby Newbietube » Tue Dec 14, 2010 7:16 am

Hi all I'm utterly baffled by this and thought maybe someone on here might have an idea of what to look for. Basically the problem is that the master volume on a Marshall JTM30 is working in reverse. I've checked the Vol pot, even took it out and all seems well. Its pcb mounted so its not like its been wired in reverse. The only other thing that affects the master vol is if the connection to the emulated line out is dissconected and that renders the vol totally inoperable but does let sound through. Looking at the circuit diagram the only other thing I'm suspicious of is the treble control as that is the last thing in the chain before the master vol.
Anyone with the slightest idea please let me know as the owner is pressuring me to fix it as he wants to sell.
Many thanks
Cheers Just
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Postby TomMcNally » Tue Dec 14, 2010 9:00 am

I'd look for a broken trace on the circuit board, especially on the ground side of the control.
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