[NJARC] Advice Needed:

[Jim Whartenby]

Greetings Joe
Warm is good.  Looking at the transformer heat "problem" from another
point of view, if the transformer was was 101% efficient, the longer it
would run, the colder it would get!  Small transformers have around 85%
or so efficiency so you have to expect it to get warm from the
remaining 15% which consists of the iron and copper losses.

If the insulated wires connected to the transformer have cracked cloth
or rubber insulation, use some varnish as a glue to stabilize the
insulation.  Opening up an old working power transformer will only
cause more problems.  Better to leave it alone.

As for the tar, it is there to keep the windings and laminations from
vibrating.  Most power transformers are dipped in varnish or some other
agent for the same reason, to keep everything from vibrating at 60cps.

So if the transformer only gets warm to the touch and you don't hear
much of a buzz from it, don't be concerned. Just enjoy the radio!
Regards and have a Happy New Year,
Jim

--- JOE CRO <n3ibx at verizon.net> wrote:

> My question is what do I do with the power transformer? It does run
> warm after playing it for an hour or so. I suspect some of the heat
> being generated is by convection from the tubes that surround it. I'm
> just concerned that it's inevitable that it'll eventually short out
> or become defective; unless I "re-pot" the transformer with some sort
> of insulating material. 
> 
> Has anyone else in our group come across a situation like this? If
> so, what did you use to repot the transformer? I was thinking of
> silicone RTV, but due to it's curing properties I don't know if it
> would be a suitable medium to use. Should I just leave it alone and
> hope for the best? Again, any advice will be greatly appreciated.
> 
> Many thanks in advance for any advice, and a very Happy new year to
> all. May 2008 bring you more radio that glow in the dark!
> 
> Joe Cro N3IBX