Higher voltage on the cathode meant darker trace, equivalent to lower voltage on the control grid. Does the board feed video to the crt grid or cathode?
The signal goes to the cathode, however, there is some additional circuitry between where I measured it and the tube itself.
If it's a video monitor, I would check at the brightness/contrast controls and see if they do anything.
I've played with every trim pot there is on the board, as well as following the factory adjustment procedure. Interesting note with that, there is a point where it says something like this:
1. Set gain pot to maximum gain.
2. Adjust "Threshold" pot until W303 (test-point) reads 2.0 +/- 0.1 volts.
When I did this, the test-point read 18V! No matter how I adjusted it, I couldn't get it below about 16V. I should note that this procedure was for the 9354A, but its my understanding that they're just about identical except for 2 more channels populated on the main sampling board.
A shorted video driver transistor (depends if CRT is cathode or grid-driven), or loss of DC bias for CRT cutoff is what I would look for.
Maybe this be causing ^that^? I've done a pretty visual inspection, but havent seen anything. Whats the best way to go about finding a shorted transistor otherwise? (i.e. can I just probe them with a meter, test the forward drop, what am I looking for?)
hum does it have some color inversion of some kind, on my scope, the lcd display background can be inverted, black / dark became white / pale "ish" and the white is darker
Yeah this is exactly what happening. Ive looked through every menu and searched all around but I'm pretty sure this isn't a "Feature"
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