[Amps] LK500ZB (2 x 3-500Z), most likely cause of zap/arc?

[Carl Clawson]

>  
> Thanks all for the good advice, on- and off-list.
> 
> Closer inspection shows a new-looking crack along the edge of 
> the HV bypass cap at the bottom of the plate choke. Also, 
> that area is very well coated with accumulated dust. I will 
> kick myself for not cleaning it up at the outset.
> 

And thanks again. The cracked bypass cap was a red herring but I replaced it
anyway. It was arcing across the plate blocking caps where there was a
distinct carbonized trace situated just where it was hard to see until I
bent them around to get a closer look. The suggestion Carl made to look for
marks left by the arcing was key...I couldn't find a mark anywhere else. Amp
works fine now after replacing the caps. No idea what may have caused the
first arc. Dust buildup, parasitic, ???

I may have lost the grid current meter on the last bang. It's not reading in
either Vp or Ig position. It's pretty well protected and hopefully I'll find
it's just a bad connection, but...we'll see.

73, Carl WS7L