[Amps] RE: burnt-looking adhesive/sealant ... ?

[Will Matney]

Mark,
The plate choke looks to have a bunch of corona dope or black silicone 
adhesive around its base. I would say there has been an arcing problem 
here. More than likely, the windings on the choke were loose and they 
added the adhesive to keep them in place. Whey they put it on the top of 
the blocking capacitors is beyond me. The parasitic suppressors have 
been replaced also. By the looks from everything, parasitics have been 
what's caused all the problems of the arcing. That amp has been 
"retired" and the HV power supply used for something else. Your looking 
at a lot of cleaning to get it back to where it once was. Besides, 
without looking underneath the chassis, I'm afraid what might be there 
too! The tank coils should be cleaned with a tarnish remover, then 
sprayed with a polyurethane varnish to prevent corrosion. The tune and 
load caps should be cleaned well also. Especially where the wiper meets 
the plates. It looks like it was once blower cooled with chimneys. The 
chimney clips are still there by the looks of it. If not, a big fan is 
needed to blow directly on the tube envelopes. Fan cooling is necessary 
underneath to keep the tube pins cool too. Last, make up a new set of 
parasitic suppressors for the tube anodes. Finally, there's no way of 
telling how good those tubes are. In the end, I wouldn't spend very much 
on this item, maybe $100 at the most.

Will Matney