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Eric,
I don't know about this business of a compressed are in the screen center. But it seems that it might have something to do with the B+ boost. Somewhere around the center of the horizontal sweep line the yoke mag energy has all dissipated and the horizontal output tube starts to conduct again. If there were something screwed up with the B+ boost, like the boost filter cap., there would be a discontinuity in the sweep at this midmoint in the sweep.
Duting the active part of the horizontal sweep there is almost a constant voltage across the yoke winding. If the B+ boost cap voltage were drooping off during the retrace and the first part of the sweep line, there would be low voltage across the yoke until the H O tube could get the capacitor back up to where it's supposed to be.
On the Sam's, this capcitor is C57 for the Setchel P66, and C73 for the P-61. It's a 0.1ufd ceramic. I don't know quite how a ceramic could lose it's capacitance, but
this is my best excuse for what might be going on. I suppose the damper and HO tubes could also be suspect, and of course something crazy could be going on with the HO grid drive, but ths would be really obvious with a scope.
Maybe we need to trade set's problems. Your set's problem is not a designed-in problem.
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CORK
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