[Amps] 3-500Z convertion

[Peter Chadwick]

Rich said:
>no, I thought he said only one of the two tubes was bad.<
Major confusion here........I thought he needed to replace both of them. From what Karl Arne said, it sounds a bit as if the 4X500 is 4-250/4-400 with a different base and an external anode. That makes them sound attractive, except for the fact that the shape of them is awkward - the anode cooler comes down very close to the glass envelope. I've a vague memory that they were originally meant for use in FM BC tx's, with a copper pipe tank circuit, down which the air was blown, but memory may be playing tricks. However, such a tank circuit would cool them effectively, although you'd need another fan on the bottom for the filament seals. They came out in about 1946/7 time.
Still sounds like a major mechanical project on a TL922.
73
Peter G3RZP