I'm having trouble with a Stromberg Carlson

I'm having trouble with a Stromberg Carlson

Post by Tim » Thu, 30 May 2002 02:39:46



Well, I finally got around to re-capping my large AM/FM Stromberg
Carlson. When I first got it, it "played", but only on the AM band and
with weak sound. On Sunday night I got around to recapping it, and
replaced nearly all ( except the tone cap and a small one
inconveniently located under the RF coils ) the capacitors, including
some small ones that looked like resistors, except for tan colour and
the mmfd. # on them. After doing all this, I was able to recieve AM
more clearly and louder, but on a badly tuned station the presence of
an annoying heterodyne whistle is soon noticed. As for the FM, with an
external antenna, I was able to recive 2 stations, from about 105 -
108 megacycles clearly at a barely audible level with the volume all
the way up. As for the rest of the dial, it is silent. Tried to see if
it would pick up a signal from my FM signal generator (FINALLY I get
to use it!) and it wouldn't recive it, even after checking to make
sure the signal generator was set to the right frequency and
attenuation on a modern (80's) FM stereo radio. Well, I decided that
this was a major victory over what I began with, so I put the radio
back together and reinstalled it on its table again, figuring I would
let it run and work out any kinks. Everything was Ok at the beginning,
but then the FM would start out strongly, play clearly and fairly
comfortable for a minute or so, and then slowly fade away. Letting it
play on the AM band seemed to cure the FM's ails, as when I turned the
bandswitch back to FM it would play for a little bit, but *aaarrrghhh*
then fade out. The FM would not work w/o an external antenna either.

I have no clue as to its model #, but it is tall, hs 4 knobs( a
bandswitch, ON-OFF-Vol, tone, and tuning ), a pale yellowish-ivory
cabinet, a couple of tubes ( 12H6, 35L6, 12BA6 x3, 12BE6, and
12dq6???? ), an unusual interlocking back that has a metal part
sticking out from it that must be inserted in the radio for it to
play, and a somewhat recessed speaker w/ gold "cloth" and below that
the dial.

  Any and all help will be warmly welcomed!

 
 
 

I'm having trouble with a Stromberg Carlson

Post by Robert Case » Thu, 30 May 2002 03:06:11


A possibility is that the FM front end tube has cathode poisoning.
This can happen if the heater is operated for long periods of time
without B+ applied to the tube, i.e., if the radio was used to listen
to AM all the time.

 
 
 

I'm having trouble with a Stromberg Carlson

Post by Tim » Thu, 30 May 2002 07:22:57


Hmmm... That's certainly a possibility. I'll see what luck I have
swapping the tubes about. I also noticed that replacing some of the
12BA6's improved performance significantly.

I will update as soon as I get done adjusting, tweaking, and tube
swapping.

Quote:

> A possibility is that the FM front end tube has cathode poisoning.
> This can happen if the heater is operated for long periods of time
> without B+ applied to the tube, i.e., if the radio was used to listen
> to AM all the time.