RadioBanter - View Single Post - Hallicrafters s-38C question

March 5th 04, 06:32 AM

r (Mike Knudsen) wrote in message ...
In article ,
writes:

Hello Chris,I think you should examine the RF coil assy. and check for
open circuit in BC input...think about this, If this receiver had an
external antenna connected and was sitting there on the BC
band,turned off,and a lightning charge came along it would most likely
burn out the BC RF coil,making it extremely weak on that band.

This is good advice -- check that primary.
I'd like to add that many antenna primaries get blown out because someone
discovers that a ground makes a pretty good antenna -- because it's using the
hot side of the house power wiring as an antenna. If your line bypass caps are
leaky, you'll get excess AC current thrut he antenna to ground -- I've seen
sparks thrown, not big fat ones, jsut enugh to let you know it isn't good for
the coil.

And if you have a fancy antenna system with a baluyn coil, then for 60 cycle
AC, the "hot" antenna lead is as good as ground, so be sure to hook up the
ground side first. Which is just hte opposite of what PL-259 coax connectors
do ,,,
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

Thanks everyone for the advice. I have since replaced all but one of
the wax caps and lamentably, the AM band is totally shot now. All I
get are two very strong stations and then WMAL, which I used to get
fine, is all but dead (it usually comes in at 630 AM, but now for some
reason it is tuning in at 500 and very very faint...) I'm a total
novice at this but I guess it doesn't take a novice to realize that
this thing is horribly out of alignment. I am really going to need to
teach myself how to do an alignment. I just hope I don't electrocute
myself! ;-) Does replacing capacitors necessarily throw a radio's
alignment completely out of whack like this?

I hope I used the right kinds of capacitors to replace the old wax
caps. Although I am positive I ordered the right values (voltage, mmf,
etc.) and triple checked everything when I replaced the old ones, I
hope I got the right type of materials. I got mica caps from Mouser
and AES when available, but there was one caps that I got that is a
"polyester film" capacitor.

Also a question about tolerances -- how important is it to get a
capacitor with the exact tolerance? When I'm looking up part numbers,
sometimes a capacitor won't list any tolerance at all; other times, a
tolerance is listed (Say, 10%) and that's the only one they have with
the voltage/farad spec that I need, but the radio's parts list
requires a 5%. Will performance/safety be affected adversely if I go
with a capacitor with a 10% tolerance instead of the required 5% ?
Maybe it's a silly question, but it's hard to find some of these
tolerances, at least in my experience.

Thanks for putting up with these questions.

-chris