I'm having X-axis collapse on the 6100 in my Tempest again... same thing I've seen several times in the past, Fonzie test or tapping the deflection board with a ruler 'fixed' it temporarily. Went in and repeated what had fixed it for about a year: removed and reflowed the X side frame transistor connector pins, and also cleaned off a bunch of old flux that had accumulated during many repairs; no change to the collapse (actually the spot killer went from intermittent to permanent). Pulled the board again and reflowed the two big x-axis transistors, now I have half collapse (left or "top" half), so at least that's progress.
Frame transistors and the two X deflection transistors all test out okay, good continuity and no shorts found in the reworked joints. Any suggestions welcome.