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tube amp being weird -- any ideas
tube amp being weird -- any ideas
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Old 11th March 2008, 06:51 PM   #11
pedroskova is offline pedroskova
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Have you swapped the KT88's between channels?
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Old 11th March 2008, 07:49 PM   #12
soundbadger is offline soundbadger  United Kingdom
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yep, i have also tried some el34's and same problem.
i have also changed the pre-amp tube i have tried 6n1p and e88cc in there. still the same problem.
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Old 12th March 2008, 12:30 AM   #13
pmillett is offline pmillett  United States
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Originally posted by soundbadger
Most likely is that either the coupling caps are leaking or the grid resistor is too large (see above). Both cause the grid voltage to drift above 0V.

the bias resistors are also pretty hot, i measured them about 70 degrees centigrade
70C is not hot for a power resistor. that's it's job - to turn electric energy into heat. Many WW resistors are designed to run at at 150C or higher when operated at rated power.

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Old 12th March 2008, 01:08 AM   #14
SHiFTY is offline SHiFTY  New Zealand
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Try temporarily replacing your coupling caps to the output valves. I've had near new ones that failed.
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