Ge 21c2465

[davet753]

Banderson: I think the 1B3 was developed as an improvement on the 1J3. Seems like I read somewhere that the filament on the 1B3 tubes were designed a little huskier than the 1J3. Because the tube usually takes it's filament voltage from a loop on the flyback, the voltage varies quite a bit. Adjustment of the horizontal drive control, brightness, or even variations in line voltage can have quite an effect on filament voltage for the HV rectifier. In other words, plenty of voltage variation for a filament rated for 10% variation.

I have read that in cases with high failure rates, you can change sockets (and filament resistor) and use a 1AX2 tube. The 1AX2 is a much more rugged tube with a tougher filament and a shielded cathode.