[R-390] Testing mica and HV caps

[Bob kb8tq]

Hi

You can do a pretty good job with a HV supply, a series resistor, and a DVM. If the cap will hold voltage
for a few minutes, it’s probably good. ( = they fail as a short and only open up if you don’t have
the current limiting resistor). For RF caps, a resistor in the mega ohm range will still charge them up 
quick. It is unlikely that you will blow one wide open at < 1 ma. 

Bob

> On Feb 27, 2019, at 12:56 PM, Perry Sandeen via R-390 <r-390 at mailman.qth.net> wrote:
> 
> Yo Bubba Dudes!
> Tisha wrote: 
> You pretty much need to test even the new or NOSmica caps. I have used
> 
> quite a few in high voltage pulse shaping networkson photomultiplier tubes
> 
> for gamma ray spectroscopy applications that werebrand-new-bad.
> OK, Good idea.
> How did you do it?  Most capacitance meters now are low voltage units.  I do have an old Sprague TO - 6 that does do a HV test but it in on that to do to get it operating list.
> Regards,
> Perrier
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