[NJARC] Advice Needed:

[Mike Feher]

Joe -

My advice - leave it alone. If you checked the total current demanded from
that transformer based on the circuit, and you are not exceeding it by much,
then, there is really nothing you can do. The tar just melts over the years
of many hours of use. It really served no purpose anyway. It is not like it
is a good thermal conductor and will get the heat out of the transformer. It
kept the leads in place and acted as an insulator. Since there was no AC
current drawn when the rectifier was out, you do not have any shorted turns.
So, again, unless you are going to use it 24/7 as your main radio, I would
not worry about it now. Glad you brought another one back to life. HNY -
Mike 

 
 
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960
 
 

-----Original Message-----
From: njarc-bounces at mailman.qth.net [mailto:njarc-bounces at mailman.qth.net]
On Behalf Of JOE CRO
Sent: Tuesday, January 01, 2008 7:56 AM
To: New Jersey Antique Radio Club
Subject: [NJARC] Advice Needed:

Visit our web site - See http://www.njarc.org
_______________________________________________
Happy New Year and Hello to All,
                                                I finally got a "roundtuit"
and worked on one of the forgotten orpans of a console radio, namely a
Philco 41-290 I picked up at one of our club auctions sometime ago. Besides
doing a complete recap, needed tube replacement, even replaced the audio
output transformer, etc etc I noticed the power transformer coughed up most
of it's original insulating tar on the wooden base it sits on. Having
previously read somewhere that Philco's are notorious for having bad power
transformers, I approached powering the set up with a bit of caution. I
first pulled the rectifier (#84 tube) and powered the set up on a variac to
see if teh transformer, or anything else would smoke up. Nothing. Good, on
to the next step. I then ramped up the AC voltage again with the rectifier
tube installed. (as a sidenote, the original rectifier tube didn't have
filament continuity - a bad sign that it may have been taken out by the
transformer or other components) and still no smoke. I then went through and
did a total paper and electrolytic capacitor replacement, etc etc, and the
set came to life. 

Needless to say I was very pleased to now have another good player in my
stable of old consoles. I'd like to add that the audio sounds terrific from
it's push-pull 41 output into a 14" speaker and correct replacement audio
output transformer. 
My question is what do I dfo 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
                            
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