[AMRadio] Seeking advice on testing modulation transformers


Mike Sawyer w3slk at uplink.net
Thu Sep 21 21:34:15 EDT 2006


I think 1KV would be ok to check for moisture. To be rid of any ambiguity, I 
would go to at least 3~5 KV. You can figure on being overrated for the 
service. Let's face it, most of your finals will run upwards to around 3.5 
KV unless you got 4-1's X 4-1's. With that kind of rating, you are in your 
ballpark.
Mod-U-Lator,
Mike(y)
W3SLK
----- Original Message ----- 
From: "Mark Foltarz" <Foltarz at rocketmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Thursday, September 21, 2006 1:38 AM
Subject: Re: [AMRadio] Seeking advice on testing modulation transformers


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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