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Old 28th March 2013, 08:47 PM   #11
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The pots are fine. I checked them with a DMM. All are secure and happy. Except one has a broken shaft, but still functions.
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Old 29th March 2013, 02:37 AM   #12
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It sounds a lot like the clean signal not getting through, have you checked voltages? do you have access to an oscilloscope?
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Old 29th March 2013, 02:40 AM   #13
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No scope. What voltages would I be checking. Not familiar with tube gear, only solid state, so I will be learning.
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Old 29th March 2013, 02:41 AM   #14
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B+ and filtering
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Old 29th March 2013, 02:43 AM   #15
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You said you tapped the power tubes with a pencil? what about the preamp tubes? are they new?
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Old 29th March 2013, 02:45 AM   #16
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Didn't check the preamp tubes, however the owner took a shotgun approach and replaced ALL the tubes (preamp and power) So I doubt they are the issue considering shotgunning it didn't fix the problem.
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Old 29th March 2013, 02:52 AM   #17
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That does kinda sound like Power supply hum too, but still that clean signal sounds like its dieing somewhere in the preamp, bad coupling maybe?
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Old 29th March 2013, 02:54 AM   #18
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I also asked on AudioKarma, and the folks there strongly suggest replacing the filter caps. I guess they have a hard life, and don't last that long?

Would I check for AC ripple, or is that not what the issue would be with the filters?
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Old 29th March 2013, 02:56 AM   #19
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not sure what preamp tubes he went with, but you can try pulling them out and swapping them around to see if he it goes away or changes, maybe one of them is really bad/went horribly microphonic.
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Old 29th March 2013, 02:59 AM   #20
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yeah you wanna see if excessive ripple getting through
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