DuMont RA-102 vertical transformer bad?

[Phil Nelson]

Well, the screen image is definitely unstable, although I'm not sure if I would ascribe it only to the vertical. The whole image seems to expand and contract in both dimensions -- horizontal and vertical -- slightly and rapidly. I can also see faint "retrace"-like horizontal lines, both light and dark. It's hard to capture with cellphone video, but these brief clips give an idea what's happening:

http://antiqueradio.org/art/DuMontRA...ngScreen01.mp4

http://antiqueradio.org/art/DuMontRA...ringScreen.mp4

Edit: I just noticed that the "retrace"-like lines are light in the top half of the screen and dark in the lower half. ????

I wonder if instability in the high voltage supply could cause the fluttering in screen size? Adjusting the Regulator Control and Voltage Control on the power supply chassis doesn't affect this problem. My high voltage meter shows a steady 10KV output, although that meter may not be sensitive enough to show such small, rapid fluctuations.

Ideas? The RA-102 service manual with schematic is at:

http://www.earlytelevision.org/pdf/d...-rider-tv1.pdf

The HV section in this set needed repair beyond the usual caps & resistors. The previous owner tore up the HV output transformer and did other odd kludges, but Andy Cuffe was able to repair the transformer and it seems to function normally. I have done extensive work on the rest of the TV. In the vertical & horizontal sweep sections, I have replaced nearly every cap and resistor.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html