[exray]

Reminds me of a buzzy Z-nith chassis I once worked on. Apparently it had been an ongoing problem because a previous repairguy had replaced the 6F5 G with a 6SF5 and rewired everything accordingly. Still had symptoms like you describe. Get anywhere near the wiring and the increase in hum was noticeable.

Ole Luddite me put it back the way it was supposed to be, did the routine resoldering of things, ran a new shielded grid lead and somewhere in the process I fixed it. Can't rightly say what the initial problem was but once it was cured all of the finickiness went away.

-Bill