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24kilo 10th April 2006 10:47 PM

Tube voltage help
2 Attachment(s)
On the Plates of the 12ax7 it's supposed to be 65 volts respectively.
But on mine it reads 63vdc pin 1 53vdc pin 6. Everything looks ok execpt the one of the 470k resistor read 460k, Other than that I can't find anything wrong. Any Help please. BTW all caps have been changed. and the Rectifier has been changed to diodes, With a bigger droping resistor R12 to get the voltage right.

anatech 10th April 2006 10:57 PM

Hi 24kilo,
Have you tried a new 12AX7? You have to remember that a dual triode is a pair of tubes that are individuals. They are not matched. I will assume the caps were changed with new poly types.

What exactly is the problem you are having?


Geek 11th April 2006 12:35 AM

470K to 460K and 65V to 63V is moot. But at that low plate voltage, 53V can be significant.

Can you swap a couple of 12AX7's and re-measure?

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