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Old 10th April 2006, 10:47 PM   #1
24kilo is offline 24kilo  United States
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Join Date: Aug 2005
Default Tube voltage help

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.
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Old 10th April 2006, 10:57 PM   #2
anatech is offline anatech  Canada
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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?

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Old 11th April 2006, 12:35 AM   #3
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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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