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I tried the alternate tube yesterday. It worked in that nothing overheated and the
voltage generated was down nicely. Unfortunately it was down to 1/3 or thereabouts,
which surely generates sync/AGC/color killer pulses that are too small.
Another method, after looking at the tube curves, is to cut the screen voltage.
The waveforms I saw on both tubes were clearly "switch" action, i.e. Class C
operation. Thus, cutting the screen voltage is just like screen modulation
of a Class C AM radio transmitter and should work nicely. Only a modest cut is needed. The chassis has to be removed anyway to properly install a new fuseholder in the power supply area, so I'll add a power pot on a temporary bracket.
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