[AMRadio] Tranny Test

John Lawson jpl15 at panix.com
Mon Feb 19 15:38:01 EST 2007

   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.



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