Quote:
Originally Posted by old_coot88
If you put an ohmeter on the control, from the wiper to the 'top' end (which goes to pin 3 of the 12AU7) and rotate the control, the meter should reveal any rough spots or drop-outs. An analog meter is preferable as its needle will follow the control's rotation, while a digital meter just gives a bunch of hard to follow jumping digits.
Actually the resistor will give you minimum gain (contrast), while shorting the 'top' end of the control directly to ground will give maximum gain.
oc
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Sorry, I didn't look at the schematics close enough. The top end of the control SHOULD have low impedance to ground.