[AMRadio] Tranny Test

Rick Brashear rickbras at airmail.net
Mon Feb 19 15:45:12 EST 2007

Bingo!  That should tell me exactly what I need to know. Thanks, John!


John Lawson wrote:

>   Re: quasi-pseudo hi-pot testing of your transformer - if you have a 
> device that produces the required 800-1000 VDC - and can access that 
> voltage (such as a bench supply, one of the other power supplies in 
> the transmitter - or even a Ranger maybe) then [carefully!] attach the 
> positive lead of that source to the windings (tie the leads toggether) 
> thru a suitable microammeter and ground the tranny frame...  any 
> leakage will show up on the microammeter. A panel-mount 0-20 uA DC 
> meter, mounted on a piece of plastic, will do.
>   If you use a DVM - just insulate it well - put it in series - don't 
> let any part of it get near ground or you - set the meter, step back - 
> turn on the HV - check the reading.  Shouldn't be very many microamps 
> to ground. Note that any significant ripple, or other AC disturbances, 
> in the HV source, will confuse the reading, due to capacitive and 
> inductive coupling of those components.  Use 'pure' DC.
>   Remember to tie the transformer HV leads together - the object is to 
> measure any current flow from the body of the windings, thru the 
> insulation, to the frame - NOT from one side of the winding to the 
> other - which would only be a few ohms DC resistance.
>     Cheers
> John
> DM09fg

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