Just picked up an Emerson 600/639 Electrostatic

[mbates14]

I may be needing a replacement 7JP4, I dont know yet. The cathode looks pretty blue/black at the tip.

The ETF had 2 according to the spreadsheet, but he replied saying he doesnt have any so his sheets are not up to date.

Edit: Now that I think about it, I should just pull out my VT-71 chassis which I haven't finished 100% yet, and test the tube that way. I really need to get a CRT tester.

[dtvmcdonald]

Its quite OK to use ceramic HV caps in these sets. Note that no use
of the very HV ones should have AC across the cap. If you use caps
at say 85% of rated voltage you just need three times the listed capacitance.
At 50% of rated voltage twice the listed capacitance will do.

I've used them in both a Pilot 37 and one of these Emersons and they
work just fine.