[Amps] Weak Amperex 3-500Z

[Peter Chadwick]

Keith said:
>Is there anything that can be done to rejuvenate the weak tube?  Or, is it
just worn out? <
It sounds as if the emission is low. Over the last 60 years or so, there have been a number of articles on recovering thoriated tungsten filament tubes. No guarantees are offered, but the process (which varies somewhat from author to author) are to run the tube (with no other supplies connected) with twice filament voltage for 5 minutes, then at 75% over voltage for 10 minutes, 5)5 over voltage for 15 minutes and 20% over voltage for 15 minutes. Some authors recommend fewer steps, and the times vary. There are no guarantees, but I remember an article in Short Wave Magazine in the early 1960s. The author had been given a dozen 813s: two were good, and 7 of the rest were rejuvenated by this procedure - or one similar.
The idea is that the high temperature makes thoria 'boil' (very much the wrong word!)  to the surface of the filament.
Very definitely a case of 'YMMV'. But what have you to lose? It may become an ornament, or it may work DX.
73
Peter G3RZP