[Milsurplus] No.19 MkIII

[wf2u at ws19ops.com]

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

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
Quoting "J. Forster" <jfor at quik.com>:

> I don't think so. A modest overfusing will cause the magnetics to fry as I
> said, but a shorted resonating capacitor would blow almost any fuse
> instantly.
>
> Anothe possible cause of overheating might be a resonating capacitor
> strapped for the wrong line frequency. (50 v. 60 Hz)
>
> Best,
> -John
>
>
>> For sure, re. the overfusing. Initially, I made sure the fuses were as
>> specified by the EMER. I suspect that in the fried unit another reason
>> could be a shorted resonating capacitor in the ferroresonant winding.
>>
>> Meir WF2U
>>
>> Quoting "J. Forster" <jfor at quik.com>:
>>
>>> The reduced line voltage may help some, as there is a ferroresonant
>>> regulator in the unit. Lower line may reduce its internal dissipation.
>>>
>>> My advice is still do not overfuse the AC, in case a 6X5 gets leaky H-K.
>>>
>>> FWIW,
>>> -John
>
>
>