[Milsurplus] No.19 MkIII

[J. Forster]

> I didn't mean a complete dead short, just enough leakage as to load
> the magnetics but stay within the maximum fuse rating.

I'm not so sure. It is a metal cased oil capoacitor, rated for AC service.
If it dissipated too much, it'd go BANG. That type of cap rarely changes
value much either.

> Is it reasonable to believe that many PSU's blew because of the
> incorrect line frequency strapping, like using them in Europe then
> shipping them back to Canada without checking them so they get
> surplussed and the users just plug them in with the strapping set at
> 50 Hz - however, I'm not sure thy were over there due to the small
> numbers. AFAIK they were mainly used in repair depots.

I think they were more likely used for fixed base operations. AFAIK, the
WS-19s were widely distributed to non-AFV situations post WW II. After
all, they were pretty good, rugged, and maintainable sets until maybe the
1960s. And there was a large installed base w/ many trained operators and
logistical support long post war. With a good, long wire antenna, they
were capable of decent range too.

> Of course even that won't burn up the transformers if they're
> adequately designed. In the early 80's while I was still working in
> the electronics industry as a design engineer, the solid state
> kilowatt HF amplifier I designed to match the marine/commercial
> transceiver my company was manufacturing, I chose to build the 50 VDC
> linear PSU around a ferro-resonant transformer. It complained when the
> frequency was wrong but didn't self-destruct...
>
> 73, Meir WF2U

The one I have unpotted and unwound had evidence of arcover in one of the
HT windings. It clearly had shorted turns before I opened it up. Likely
the failure is a result of overheating and HV breakdown, not a single root
cause. High line may make both failure contributers worse. Anyway, I think
we can agree that the AC PSU's are pretty marginal, although very nice.

FWIW,
-John