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.

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.

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.

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.

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.

Steven P. Burrows wrote:
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.

That is correct, it is not a big problem, it is a *HUGE* problem.

Most of these older radios were designed for a 115V nominal power line
voltage. Today, people complain if the voltage is as low as 120V at the
outlet. It is more typically 123 to 125V. That means that even using the
original transformer, you will have nearly a 10% more B+ voltage than the
designers envisioned. So, your +225 will be +240V. You are running 50
more than spec, so your +225 will be +275, which will kill the caps and
shorten the lives of the tubes in your radio. (OBTW, the voltages I used
in the above description are just guesses. I am not certain what the
actual design voltage is for your radio.)


....

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.

It was most likely damaged by the manufacturer. It is easy to nick a winding
through careless handling. The problem usually occurs where the inside end of
the primary (or secondary) crosses the windings to get to the outside where the
leads are attached. You can often cut the bobbin away, and find the short.


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.

Intermittent arcing is unlikely. Because of the relatively high currents,
and low voltages involved, it will usually burn off a wire, or weld it
permanently together.


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.

Transformers are relatively immune to voltage spikes. For reasons of
manufacturing economy, the core is usually run right on the edge of where
it starts to become nonlinear (eg. saturation is beginning). If a spike
comes down the line, the spike will drive the core into saturation, and
that simple act will prevent the spike from being "transformed" to the
secondary. A lightning strike is a different matter. It will usually
cause an arc from the primary lead that is closest to the core to the core.
The lead will often be vaporized.


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.

They are a hoot! Welcome to the BA addiction/disease.

-Chuck

"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

"Steven P. Burrows" wrote:

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.

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.

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.

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.

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.


If the B+ is higher, the current load on the transformer goes up,
too. That higher current on the HV winding may have been more than the
transformer was built for.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida