[Milsurplus] No.19 MkIII

[Ralph Cameron]

The unit I had was brand new and purchased separately from the main unit. 
That was because I was tired of renting car batteries to run the dynamotor 
at 50 cents a day. I didn't have a circuit of that AC supply so never knew 
what was in it . All I know is it stopped putting out HV one day accompanied 
with the smell of tar. When I opened the unit up, it had obviously gotten 
very hot. and never recovered. I didn't know it was a ferro-resonant supply 
but the wrong frequency could overheat it.

73
Ralph
----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: <wf2u at ws19ops.com>
Cc: <jfor at quik.com>; <milsurplus at mailman.qth.net>; "Ralph Cameron" 
<ramcam at magma.ca>
Sent: Monday, February 16, 2009 3:31 PM
Subject: Re: [Milsurplus] No.19 MkIII


>> 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
>
>
>
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