1948 Capehart trouble

[kbmuri]

I'm working on a '48 Capehart. I didn't recap this one, but I respect the abilities of the person who did recap it (a fellow AKer). I had it shipped cross-country via a mover (North American Van Lines) but it doesn't appear to have taken any abuse. It had no CRT, so I put in my own untested used 10BP4. I bought the CRT from a different AKer who said it tests 100%. I think it probably does, but still don't have a CRT tester that I trust. After adjusting the ion trap magnet I get a nice bright screen and full raster. It's a radio/TV/Phono combo and I haven't checked out the radio so I can't say how the TV's audio is (it uses the radio's output stages). The radio isn't recapped yet. The phono is completely missing. The cabinet is rough but complete.

So the TV looks pretty good, but every couple of seconds I hear an HV "snap" and the CRT screen darkens, then recovers. In the dark I'm seeing an arc inside the neck of the CRT at about the point of the ion trap. It seems kind of violent -- destructive enough that I don't want to let it continue, for fear of ruining the nice 10BP4. Unless the 10BP4 is already ruined and that's why it's doing it.

Anybody have any suggestions?