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Duh on the series resistor. Then why did Philco say to bypass part of the ballast resistor for the 6.3V tubes?
OK. So I might as well try an external rejuv circuit, what have I got to lose? Opinions on which circuit or techniques to use in a last ditch effort?
On the next expedient. I do have a 21FAP4 NIB. In other threads the thought was that this tube should work but nobody had yet, at least as far as I could see. Looking at the data sheets, it seems the main difference is that the 21EAP4 has an extra grid tied to the anode. And that G1 and G2 pins are swapped and that G3 on the 21FAP4 is the same as G4 on the 21EAP4. So does all of that boil down to swapping G2 & G3 on the CRT socket?
Thanks!
Jonathan
After thought: What about putting a 3.9 ohm resistor in place of the CRT filament and then making a separate power supply for the CRT filament?
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