Quote:
Originally Posted by Username1
If pin 7 is at -5v as you said early on, then the first video amp
tube v4 is close to cutoff. Cutoff is where the tube does not
conduct any current, that would explain the high voltages
on the plate & screen grids. I would wonder if the 22ohm
resistor in the cathode circuit is open? or there is a
bad connection, broken foil etc. Why is -5v on pin
7? bad resistor to ground up stream closer to
the detector? For the most part the picture looks
good, and you have color, so it's all pretty much
working. So it's gotta be a little thing......
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Yep, not only the voltage on pin 7, but 8 and 9 are way out of spec from the schematic. R56, 22Ω is within spec too. The 100v and 390v rails measure correctly. I replaced R58, 10k/10w even though it measured in spec out of circuit. I agree, as you said about the -5V on pin 7 producing the voltages on 8,9. That points to a possible problem upstream.
The only route to pin7 on V4 is thru the vid detector, via V3. The 200V rail that feeds the grid on V3 measured ok, but looks like I need to dig deeper and check around V3 for voltages carrying the IF signal thru the detector.