"Steven P. Burrows" wrote in message
news:lpbmg.57892$9c6.52561@dukeread11...
The B+ voltage delivered by the new transformer is about 50 volts higher
than Hallicrafters' original spec., which I was advised was not a big
problem. The other secondaries for the tube filaments and rectifier
filament were exactly right.


The "not a problem" transformer had a B+ of 25 V lower. Last year you
wrote:

"I have looked over the offerings from Antique Electronics Supply, and their
Fender transformers are a close match. Unfortunately, the Fender
transformers offered there top out at 325-0-325 V for the secondary
windings. I need a transformer with 350-0-350 V / 70 mA, 5 VAC / 2A, and
6.3 VAC / 2.6A secondary windings. "

http://groups.google.com/group/rec.r...ae22ac314cd44b




Throughout my use of this restored S-40B, I have been running it off of
a personal computer grade surge suppressor power strip, along with my
other old radios (others are solid state).

I replaced the power supply electrolytic caps with new ones, so I doubt
that this was a problem. From past experience with arcing in the
rectifier tube, I also looked into this possible cause. My rectifier
tube was also OK.

Be sure your power supply electrolytics can take the peak rectified B+. If
your new transformer is really putting out 375 V, the peak voltage is 525 V.

I'd be alot more comfortable if the B+ voltage was at the original spec or a
little below.



I pulled all of the tubes from the radio and powered it up in a darkened
room to attempt to see any potential arcing under the chassis. The fuse
blew, and there was no visible evidence of any problems in the radio
wiring.

Next I disconnected the secondaries of the power transformer from the
radio entirely. The fuse still blew.

Next I removed the safety filter capacitors from the transformer primary
circuits. Fuse still blew. I traced out the primary circuit with a DVM
and found no short circuits in my wiring or from the transformer
windings to each other or to the transformer frame. With the transformer
completely taken out of the radio the fuse blowing stopped. I was
forced to conclude that the "new" transformer was a dud.

Sure sounds like it.


I don't have access right now to a variac, but I suspect that there
might be some sort of arcing in the transformer that doesn't show up
until higher voltages are applied. I still have this transformer, and I
might try looking at it again later this year when I can borrow a variac
from the university where I work.

You can usually hear arcing. Smoke might also start coming out. It sounds
like you've got a dead short. There's a chance you might find it if you
take off the endbell and inspect the area carefully. Don't count on it.



I have replaced the suspect transformer and so far the radio is working
fine. My interest in using inrush current limiters is motivated by
trying to avoid a repeat of a damaged transformer, both in my father's
S-40B or my own.

In spite of having a fancy microprocessor based Sony SW-77 to do my
SWLing on, I find using this old 'boatanchor' type radio irresistible.
After I finish up grad school (which I am starting rather late in life -
age 46) I plan to go for a ham license and possibly look into using
other BA gear.

The S-40s are decent beginner radios in that they do work and they aren't
too hard to work on. But there are better radios out there!

Frank Dresser