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DO you have HV?? This is one thing to check for first. I believe this set powers the tube filaments through the power transformer--NOT the flyback. SO, even though the fils. are lit--HV could be absent. IIRC, this set has an 80 volt B+ line for the horiz. output ckt and flyback, ran through a regulator somewhere , not on the power supply.
If HV is ok--what does the cathodes of the tube look like?? Are they being biased off?? If there is over 175 or so on them, not varying with the brightness or contrast control--the tube is in cutoff. Often if you crank up the screens in this situation you can get a dim raster.
If in cutoff--make sure the video module is not dying. It likely has those same shitty german caps, and they may be giving up.
If not in cutoff--is the screen voltage ok?? Should be variable, somewhere up to 600 volts or so for each gun. Comes from the horiz. ckt, not sure where, likely from the H-output itself through a resistor or two.
DOn't overlook the FOCUS voltage, either. On a lot of CRT's from the "day" if you lose focus voltage--you get no raster. LIkely derived from a bleeder off of the main HV.
CHeck these things--likely you will get a clue to the problem.
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