> >My inclination is now turning toward a short from anode to ground through
> >the grid.
> >An ammeter in the cathode lead would remain at zero during an event like
> >this.
> >A tell-tale pile of grid pieces in the bottom of the tube envelope lead me
> >down this path. A purely uneducated guess eight years after the fact from
> 2000
> >miles away!
> >
> This scenario would have required broken anode cooler welds - which
> allowed the anode cooler to tip sideways and touch the grid. Terry did
> not report such an occurrence.
> If Terry still has the fil./grid shorted tubes, I can disassemble them,
> photograph what I find, and post it on my Web site.
>
> cheers, Phil
My feeling is that the failure was NOT mechanical in nature.
I have an 8877 here that trips 30 amp breakers while drawing "0" cathode
current.
(((73)))
Phil, K5PC
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