[Milsurplus] SCR-288/BC-474
Nicholas Hopper
mec1945 at webband.com
Tue Jan 3 01:15:48 EST 2012
Hello everyone!
First off, I am brand new to radios and at the moment not a licensed
operator. (Working on that) I have been an avid collector of WWII gear and
a buddy of mine thought it would be a great idea to get into collecting WWII
radios. (Funny thing is that he ended up going off the deep end and been
picking up some cool stuff - another topic for another day.) I ended up
with a fairly complete SCR-288. It includes the BC-474-A receiver, the
GN-44 generator with legs and seat, filter FL-10, mic, headphone, BA-48
battery (dead) and TM 11-250. The only thing missing was the telegraph key
and antenna. I was told it worked but of course bought 'as-is'. Oh, did I
mention I have no real working knowledge of radios (at least stuff like
this.)
I have been learning a lot about it and built a new radio pack so that I can
get the receiver up and running so that I can at least listen for now. So
I followed the direction in the manual for starting up the receiver and
bingo I heard some noise! I figured I was good to go. I was able to switch
over to CW and hear the 'tone' as a tuned to a frequency. It seemed to go
good but after a few minutes I started to get a lot of popping, snapping and
cracking and the signal would fade completely out then come back. As time
went on, the signal would fade out for more time or then I wouldn't hear
anything at all, or it would go back to nothing but the popping, snapping
and cracking. Ultimately within about 10 minutes that is about all it would
do (pop, crack and snap with no tones on CW or able to hear anything). So I
pulled the unit out of the case and started to try and trouble shoot things.
The manual has a good schematic of the receiver (and transmitter) and I
found a few things different and one item not hooked up properly(?). Also
if I touch or slightly move the TRANS - REC switch the popping, cracking and
snapping gets worse.
So, I am looking for people that might have this specific unit willing to
maybe help me do some trouble shooting. Inside the manual is a typed note
that says, "No alterations or conversions have been made with the exception
of the following: 6C4 speech amplifier stage added for more modulation.
Receiver audio output transformer changed using a 3.2 Ohm secondary rather
than the 2000 Ohm secondary in the original unit. Side-tone removed from
the modulation transformer to permit speaker operation. Wiring still in
unit if side-tone rewiring is desired."
I have no idea what this means and not sure if it plays a part in the
problem or not. I was able to confirm that the side-tone wire has been
re-attached in a different spot on the transmitter side of the radio.
So, thank you for letting me 'vent'. It has been quite a learning process
for me and I do enjoy it. I'm learning more and more each day about these
old radios and it is quite interesting. It is so much more interesting than
new stuff this day and age. I know I will appreciate it much more once I get
it figured out.
I do not know if I can attach photos on here or not. If I can, I'll attach
some pictures of this radio.
Thanks,
Nick Hopper
Newman Lake, WA
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