[AMRadio] Seeking advice on testing modulation transformers


Mark Foltarz Foltarz at rocketmail.com
Thu Sep 21 01:38:54 EDT 2006


Mike,

  I have seen some less  expensive meggers out there with voltage output @ 1 kV
and a resistance range of 1 Gohm.

   I know the resistance scale is right. I suspect the voltage although about
half of what it might be will probably produce good results.

  Do you suppose a 1 KV megger would do the trick?

Mark

--- Mike Sawyer <w3slk at uplink.net> wrote:

> Mark,
>     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.
> Mod-U-Lator,
> Mike(y)
> W3SLK
> ----- 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 
> cherished
> 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
> : 5500 surplus units,  and a mod transformer from a BC610E.
> 
>   I was thinking of applying power between case and a terminal and looking 
> for
> leakage.
> 
>   In the past I have even run a mod transformer with a case leakage on a 
> piece
> phenolic with favorable results.
> 
>   By the way, does anyone have any experience using the RCA 5500  5500 
> units?
> 
> TNX
> 
>  de KA4JVY
> 
> Mark
> 
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