[Electronic M]

I'd have kept a Zenith and dumped the RCA.....Tubes+PCBs=more frequent harder to fix troubles....As some one who runs an RCA(clone roundy) and Zenith(hybrid rect) side by side as daily watchers and has done so for 5+ years I can tell you that the RCA construction method/circuits are more of a pain to fix (and need to be more often) when they act up.

Depending on the chassis variant I probably have most or all of the tubes in my stocks. If it is a CTC-15 set I could probably sub known good tubes from one of my sets to test it.

If you have not tried the HV reg adjustment, then you should....If that don't help, pull the top cap off the HV reg tube (may need to place in a jar to prevent arcing) and see if the HV improves....If it does the reg needs work....If not suspect the HV rectifier on back to the H osc.