Predicta Picture Tube Replacement

[Indian Head]

Hi everyone

I was wondering what modifications would be necessary to use a replacement 21FDP4 picture tube in a Holiday G4242 Predicta set. This would be a replacement for the original 21EAP4. I read somewhere that the filament voltage was higher on the replacement tube. Did Philco provide instructions to update/upgrade?

Thanks for any help anyone can provide.

John Hess

[kx250rider]

I've heard that you can just swap in the 6.3 volt tube, but you have to rewire the base pinout. Evidently, since it's a series filament circuit, it will work. You can use an RCA Tube Manual to compare the base pinout, if you don't have the schematic for whatever TV the new tube comes from. I'm sure someone here will be able to call it out from memory, as to which wires need to be relocated on the socket.

Charles

[Don Lindsly]

The 21FDP4 should work OK with only a single wire change on the socket. The tube is about a half inch longer.

Drill out he rivet holding the socket cover and move the wire and connector from pin #3 to pin #6. The heater voltage is 6.3 vs 2.35, but the current is the same so nothing needs to be done. If you do it (except for the drilling) while the socket is on the old tube, the other pins will stay in place. Either tube will work when you're done.

Put the socket back together with #2-56 screws/nuts or whatever fits.

[Indian Head]

Thanks to all for your help!