[AMRadio] Seeking advice on testing modulation transformers

Mike Sawyer w3slk at uplink.net
Wed Sep 20 19:12:40 EDT 2006

    I have found that the best way to check a transformer is to use a HI Pot 
tester or an insulation tester like a megger with about 5kv capability. I'm 
fortunate to have access to a 5KV jobber at work. Anything less than 500K 
ohms would be suspect.
You could go to Rich Measures webpage. I believe he has a neat schematic for 
HI pot testing tubes which would accomplish the same thing.
----- Original Message ----- 
From: "Mark Foltarz" <Foltarz at rocketmail.com>
To: <amradio at mailman.qth.net>
Sent: Wednesday, September 20, 2006 6:53 PM
Subject: [AMRadio] Seeking advice on testing modulation transformers

  I am sure the following has happened to all of us.

  You build a transmitter or modulator using a transformer that you have had
around for years.

  You then apply power only to find  a short to case or worse on the 
modulation transformer.

  Well, I would like to avoid that with several chunks o' iron I have here.

  Specifically, I have the big Thordarson multimatch, a pair of those RCA 
: 5500 surplus units,  and a mod transformer from a BC610E.

  I was thinking of applying power between case and a terminal and looking 

  In the past I have even run a mod transformer with a case leakage on a 
phenolic with favorable results.

  By the way, does anyone have any experience using the RCA 5500  5500 


 de KA4JVY


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