[AMPS] AL-1200 Blower

[Peter Chadwick]

Bill said:
> I wonder if an infrared detector diode mounted to "look" directly at
> the anode might be better.  

A number of Marconi tx's for military and naval  applications did that for
detecting excess plate dissipation back in the late 1950's, for tx's with 4-125
and 4-250. The photocell and a 12AU7 schmitt trigger were in a fully screened
box with a mesh window looking at the tubes.

It worked fine until people started using Siemen's equivalent to a 4-250. These
had really big carbon anodes with substantial fins on them, and wouldn't glow
red enough to trip the thing at anything under about 320 watts plate
dissipation!

There was a tendency in the field to just wind the trip right up, as it was
found to be more trouble than it was worth.

73

Peter G3RZP



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