Moved to Instruments and Amps per forum policy. More likely to get an answer here anyway.
Classic Amps: The 1961 Gibson GA-79RVT
Classic Amps: The 1961 Gibson GA-79RVT
i have 2 gibson ga79rtv amps. they both sound excellent. however, one runs considerably hotter than the other. what could cause this?
thanks,
Check the 200 Ohm cathode resistors and the output tubes.
leakier coupling caps on one.
Yes, that's quite possible. Check the voltages at the output tube grids, which should be close to zero.
If one or more grids are at some significant positive voltage, replace the coupling capacitors.
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thanks to all, i've replaced the coupling caps and the amp doesn't run nearly as hot.
From 1961 it's probably still within the range of crap quality capacitors, that used to leak
With 'modern' ones it's rarely a problem, but back in the 70's it was a VERY common fault with any older valve equipment.
thanks to all, i've replaced the coupling caps and the amp doesn't run nearly as hot.
thanks again,
mikeB.
Great, I've only found leaky coupling capacitors a few times in all the old amps that I've worked on, but when it happens, they all should go.
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