Hi all,
Anyone familiar with Evil Twin circa 1988 amps??
I've been fixing some broken pots for a friend, have been inside one of these before but am a beginner with electronics (a brave one)....
Anyway, reverb wasn't working and a few pots had got smashed off so I replaced the pots and found reverb connection problem easily enough, all fixed.
While I was in there I noticed that the R128 ceramic 2.7k resistor had been replaced mistakenly by someone who had put three 8.2 resitors in parallel, yes, thats 8.2 ohm, so that must have been about 3ohms instead of 2.7k. I had the right one lying around from fixing an identical amp years ago, so I replaced that and re-biased the valves too. (spotting this resistor being wrong I don't know what it could have done to the amp but some squealing bezerk feedback had happened before with the guitar turned completely down - or so my friend told me, and he's wondered what that was.)
Anyway, here's the problem, I put it all back together and hey presto 'nothing comes out of the clean channel'... the switching to the channel is all fine, thats happening and there's the familar 'background buzz' through the speakers just as on the dirty channel that this amp always has but nothing is coming out, turning the volume control up doesn't do anything.
The clean channel volume pot wasn't one of the pots touched either
Can anyone point me at anything I can look at that might be a likely cause of the problem, with instructions I'm pretty good at checking thing out and have a good multimeter to hand too.
Help/advice appreciated.
Cheers
Mark
Anyone familiar with Evil Twin circa 1988 amps??
I've been fixing some broken pots for a friend, have been inside one of these before but am a beginner with electronics (a brave one)....
Anyway, reverb wasn't working and a few pots had got smashed off so I replaced the pots and found reverb connection problem easily enough, all fixed.
While I was in there I noticed that the R128 ceramic 2.7k resistor had been replaced mistakenly by someone who had put three 8.2 resitors in parallel, yes, thats 8.2 ohm, so that must have been about 3ohms instead of 2.7k. I had the right one lying around from fixing an identical amp years ago, so I replaced that and re-biased the valves too. (spotting this resistor being wrong I don't know what it could have done to the amp but some squealing bezerk feedback had happened before with the guitar turned completely down - or so my friend told me, and he's wondered what that was.)
Anyway, here's the problem, I put it all back together and hey presto 'nothing comes out of the clean channel'... the switching to the channel is all fine, thats happening and there's the familar 'background buzz' through the speakers just as on the dirty channel that this amp always has but nothing is coming out, turning the volume control up doesn't do anything.
The clean channel volume pot wasn't one of the pots touched either
Can anyone point me at anything I can look at that might be a likely cause of the problem, with instructions I'm pretty good at checking thing out and have a good multimeter to hand too.
Help/advice appreciated.
Cheers
Mark
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