[thirtiesradio]

In my case (AK 92) it turned out to be a speaker wire making intermittant contact. At first I thought the 2K ohm coil was open, but it was the wire just above the jack. This would cause max B+ being felt at the - side of the cap that was failing.

Rewired the entire jack, as there were 2 more wires approaching the condition of the bad one, and am listening to the race on the AK as I write this.

Yes.... the AK sets have that rubber coated wiring that gets brittle. I have a 206 and 447 that I had to rewire much of the wiring.
I've found excessive draws that cause filter cap problems. Hopefully by using the higher rated cap and a bucking transformer it will solve the problem he is having..but if two capacitors went south there may be a draw somewhere. Both my 16B and 116 have been fine with 450V rated capacitors.....even when they were running on normal line voltages.