Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: catnine on July 02, 2011, 08:45:41 pm
-
to drift up and down not as a steady fashion but at random about 6 VDC ?
-
No its not normal. The voltage on Pin 5 of the 6V6 should be zero. Check the coupling cap (from the pre-amp driver stage) for DC leakage.
-
No its not normal. The voltage on Pin 5 of the 6V6 should be zero. Check the coupling cap (from the pre-amp driver stage) for DC leakage.
This is what happens, as the amp warms up the dc voltage on pin 5 of the 6V6 begins at 4.6 VDC as the amp warms up say 5 minute the voltage on pin 5 on the 6V6 climbs to 25 VDC then goes higher then it begins to fluctuate.
I had the DVOM on dc volts clipped to pin 5 and ground , i watched the voltage jump all over from about 20 vdc the 46 vdc . it was very difficult to track it but it was never at 0 vdc. I never thought of checking pin 5 at all. Yesterday I went over everything and then decided to check pin 5 never thinking that a new cap could be bad . I have never run across this before yet I was aware of coupling caps going bad. It didn't even register when I saw DC voltage on pin 5 . I'll drain the caps and lift the end on that coupling cap that goes to the grids 220k ohm resister to ground and turn on the amp and see how much DC it passing through the .02 cap. This may be why I have the ice pick highs.
-
Never mind , like an idiot I was not paying attention to the DVOM and it was mV not volts on pin 5 on the 6V6