Quote:
Originally Posted by Penthode
Futher thoughts.
I would think it less likely the problem is with the voltages to the 12AX22A screen or control grids unless you saw a hue change as the picker got darker.
The gradual dimming will be most likely due to the plate voltage of the 12BY7 rising gradually. Depending upon how long it takes, it will be the 12BY7 heading to cut off. It may be the control grid potental changing. Chief suspect would be R407 180K drifting upward.
The other chief suspect to me would be the screen resistor R410 22K drifting upwards lowering the 12BY7 screen voltage.
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Thanks.
I may not get to this until January, but will put these on the list of things to check first. Hope these are on the top of the boards.