Picture streaking

[old_tv_nut]

Hmmm - maybe the peak whites are drawing grid current on the CRT, and affecting the vertical grid voltage of the vertical output? A bigger value for C310 might change things, but not fix them. Too big a value would filter out the pulse that is intended to blank the retrace lines.

If you could find a negative vertical retrace pulse somewhere else, it might work and not affect the vertical sweep.

Another thing to try would be some resistance in series with the added .05 capacitor.