[Amps] questions about hi pot tester

[TexasRF at aol.com]

One useful source of high voltage parts is from old microwave ovens. In  
particular, the power transformer, filter capacitors and diodes are plentiful  and 
cheap on Ebay.
 
The filter caps are typically .95 microfarads and will easily handle more  
than 6500vdc. One transformer, four diodes in a 4X multplier and four capacitors 
 will generate approximately 13kv.
 
To prevent damage to the component under test, the current should be  
limited. One very easy way to do that is by using a Tripplett 630, set for 6kv,  in 
series with the output. The 630 will indicate full scale at a current flow of  
60 microamps and what ever the reading is in volts should be deducted from the 
 power supply voltage reading to determine the actual breakdown voltage.
 
I use a small 2 amp Variac to vary the primary voltage, allowing output  
voltage to be set over a range of 0 to 13kv. At greater than 6kv, I use two 630  
meters in series and add their readings to measure the output voltage.
 
Yes it is a kludge, but it does work quite well, especially considering the  
cost.
 
73,
Gerald K5GW
 
 
In a message dated 1/3/2008 2:37:58 P.M. Central Standard Time,  
barrie at centric.net writes:

Commander!

I was in much the same position, in that I had  gathered almost all that I
needed to build a hipot, but the filter caps  kept getting away, especially
price-wise.

I ended up buying a  commercial unit on EBay, in the "Industrial  Electronics"
section.

Continusously variable voltage from zero to 15  KV, variable load from 2
microamps on up, two big meters and looks as if it  had never been used.

$100.00, shipping included.

73, Barrie,  W7ALW
----- Original Message ----- 
From: "Commander John"  <crazytvjohn at yahoo.com>
To: "Steve Katz"  <stevek at jmr.com>
Cc: <Amps at contesting.com>
Sent: Thursday,  January 03, 2008 1:18 PM
Subject: Re: [Amps] questions about hi pot  tester


> The application is to ham radio related stuff. Not  commercial.  I do not
know what I may need to test in the future, so I  do not know what to get in
a tester.
>
>   john  w9zy
>
> Steve Katz <stevek at jmr.com>  wrote:
>   What's the application?
>
> A lot of  off-the-shelf hipot testers for consumer electronic equipment
> stop at  6kVdc (because that's the limit of the requirement for
> compliance  testing on a 240V circuit) and that's not nearly high enough
> voltage  to test, say, a high power transmitting tube.
>
> Are you looking  to do compliance testing, which requires a stipulated
> ramp time, dwell  time and leakage limit? Or just to see where stuff
> flashes over? How  high a voltage?
>
> WB2WIK/6
>
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