mesa m9 carbine distorted, intermittent output

ca7922303

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Early serial #(600's), per mesa support, changed 12AX7, jumped send/return efx loop, plugged direct into return efx loop with bass, no change. Passive good known bass, cab, and cables. Need to fix myself. Mesa wants $450.00 w/o shipping both ways. Any ideas from similar issues would be greatly appreciated. Thanks.
 
Re: mesa m9 carbine distorted, intermittent output

Bad.dirty pot maybe? Really hard to diagnose across the interwebs.

Start with the easy stuff, turn it off and turn the knobs full rotation CS/CCW 15 - 20 times, or better, if you can get to them with some cleaner.

Also while it's off, some contact cleaner in the tube socket wouldn't be a bad idea, or remove reinstall the tube a couple of times in case there is dirt/corrosion on the contacts.

That's where I would start.
 
Re: mesa m9 carbine distorted, intermittent output

Is the input jack messed up? Are the tubes glowing evenly?
 
Re: mesa m9 carbine distorted, intermittent output

Shorted MOSFETS it seems. Pulled one(1) of ten(10) and it is shorted.
 
Re: mesa m9 carbine distorted, intermittent output

Should be a pretty easy fix then if you have the skills to diagnose that. Good luck on the fix.
 
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