Don Bowey wrote:
On 6/9/06 9:39 AM, in article Dvhig.52727$9c6.47085@dukeread11, "Steven P.
Burrows" wrote:

I have been working on a pair of S-40B receivers over the last 18
months, and only recently became aware of the possibility of capacitor
failure in the IF transformer cans. Based on my reading on the subject,
I suspect that I may have one IF shorting out across its silver-mica cap.

I found a web page with a procedure for replacing these cap's, but I
have no idea what the values are. There are two IF transformer part
numbers in the S-40B, so I suspect that they have different caps.

The Hallicrafter part numbers are 50C243 (1st and 2nd IF) and 50C242
(detector).

I would greatly appreciate some help with this question.

Have you attempted to align them? What are your symptoms?

Don

I did align the IF's and they peaked up quite nicely. During the course
of aligning the 4 bands of the radio, I encountered problems with
setting 10 MHz on band 3. I was only able to get the signal down to
about 10.3 MHz before the oscillator ferrite slug was totally backed out
of the transformer.

I restored two S-40B's: one for my father and one for myself. On my
father's radio, band 3 aligned very nicely, as did the IF transformers.
On both radio's, band 4 was hopeless, so far as the low end of the dial
was concerned. The 18 MHz signal landed at about 19 MHz on the dial. I
checked which signal was the image frequency by tuning in the S-40B
oscillator signal on my digital Sony SW-77, so I don't think I was
aligning to images.

At some point last week I had to declare that both radios were as good
as I could make them, and put the cabinets back on. Sensitivity on both
radios was very good, and I could live with some dial inaccuracy.

Last night, while I was listening to my S-40B, it died on me (a fuse
that I installed in it blew) coincidentally at the same time that the
central air conditioner turned on. I suspected a power surge from the
AC switching on, so I replaced the radio fuse and it promptly blew
another. Based on an earlier experience with a "gasy" rectifier tube
that was arcing, I tried switching to a different 5Y3GT tube and blew a
third fuse.

I learned of the silver - mica migration problem late in the restoration
of these radios. My own problem with a band refusing to align without
moving the oscillator slug to an extreme position was cited as a symptom
of the IF cap problem on a web site that I found last night. I am
planning to try powering up the radio this afternoon with all of the
tubes pulled except the rectifier, just to see if it still blows fuses.

Even if the IF's are OK, and my present problem is a flaky tube,I expect
that someday I will have to deal with the IF cans anyhow. So I would
still like to find out what the internal cap values are for future
reference.