Zenith H-500 Transoceanic Quandry...

[Kico]

Just finished completely re-capping my Zenith TO H-500 along with replacing a lot of out of spec resistors. I replaced all the 1Megs at the tubes bad or not just to be sure and powered it up on my variac. At about 90V it came alive and sounded great--no hum and lots of BC stations and a few SW.

It continued to play for 2 hours or so and then just suddenly quit! At first glance it appears the filament string is dead. I checked the obvious, the new diode (replaced the SR) and ohm tested the filaments on the the tubes--all good, I'm using a 1R5 for testing so as not to put at risk the 1L6.

I'm not a diagnostic expert by any means and really need some help to determine what could have happened and what steps to take next.

Thanks guys--