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Old 26th February 2012, 07:35 AM   #1
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Default Valve stage coupling capacitor leakage?

I've constructed a simple 2-stage valve preamp (voltage gain and cathode follower).

Each of the stage works fine independently, but once i put the stages together with a capacitor the cathode follower's bias voltage changes and puts it in cut-off state.

Im suspecting that its caused by the coupling capacitor's leakage but i can't be sure, I'm currently using a 250V Metalized P.E. cap.

If it is caused by the leakage, then how do i solve it, if not then what other causes could there be?
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Old 26th February 2012, 10:20 AM   #2
SY is offline SY  United States
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A schematic would help. If you have photos, that would also be nice (it COULD be as simple as a wiring error).
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 26th February 2012, 12:26 PM   #3
DF96 is offline DF96  England
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Coupling capacitor leakage almost always turns the next valve on too hard, not off. My guess is that you have a circuit or wiring fault. A diagram would help.
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