Dark Picture/Black Bars Across Screen - RCA CTC-44A Chassis

[joeseattle70]

Turned on my beloved 1971 RCA console tv this morning, and after a few minutes, screen started getting dark and solid black bars went across screen - almost like "black out". Turned off tv, let it rest, turned on - was fine, then within a few minutes, it happened again - whenever what component gets warm failed, it became evident again. Any idea what might cause this? Convergence board was re-done last year, so should be ok - could it be the tube or another transistor/capacitor on chassis? Turned off Auto Tint and AFT to see if it was those circuits and it had no effect on it. Also tried vert/horiz hold and had no effect either. Thanks for any ideas!!! Joe