N_Cook wrote:
Any tips for doing so?
My tester goes only to 25Megohm , consistent leakage usually shows itself in
that range , would going higher by some modification elicit intermittants?
Any other tips? heating the envelope with hot air gun? holding valve
horizontally while testing ? testing at higher plate/anode voltage ?


Can't help you with a TEST, but I've had success blowing out shorts,
intermittent or otherwise, with a stun gun.

At 25M, you're gonna need to look for issues with the socket and the
circuitry hooked to it. Doesn't take a very big spider web or chunk
of damp dust to make
25M.

I once had a spider build a tidy web across a CDROM read lens...but
that's another story.

YMMV