[Boatanchors] S-38C BFO Question

[L L bahr]

Curt;
Assuming the gimmick set up is placed properly,  I had a similar problem with a S-38C I recently restored.  When I got it, I replaced parts before ever turning it on as I was sure bad things would have happened if I had turned it on before replacing parts.  I replaced three tubes replaced every resistor and every paper cap and every electrolytic cap.  Then I tried it and band D was howling and had no sensitivity and the CW switch produced the results you are encountering on all bands. I think the sensitivity in CW is down in your radio because the feedback signal is so strong in relation to the incoming signal causing your symptom and is partially blanking the received signal.  It is being blanked to some degree by this CW feedback scheme. (Over powering the incoming signal.)  Now to fix it.  I first aligned the 455 IFs and this improved sensitivity a little but not much.  Apparently the IF transformers were fairly well tuned before I got to them.  Then I did the rest of the alignment for each band with all those trimmer caps under the chassis.  Wow!  This really peaked up the sensitivity and my CW feedback was more in line with the incoming signal and the cw system seems to be working just fine.

The bottom line for me was to align the receiver per the manual and this made the difference and got the CW portion of the receiver to work just fine. (Both the incoming signal and the beat signal were evenly matched signal strength wise.)  Also note, with that feedback scheme there are two critical parts.  1 There is the big wire which needs to be fed between two pins of the same tube and then there is a gimmick wire around it.

Lee, w0vt 

PS:  This S-38C is going to be mated with your Globe Scout 65 as this was my first General class station as a kid.




subject: [Boatanchors] S-38C BFO Question

"Trying to resurrect an S-38C inherited from my father.  Recapped and hears 
AM well.  CW/SSB received well only by coupling signal generator 455 kHz 
signal to IF amp input.  All attempts to improve operation by manipulating 
the gimmick caps on 12AG7 IF input and output have  failed.  Would 
appreciate advice from anyone who has encountered and corrected similar 
issues.  The gain when in "CW" is very low."

"73, Curt KB5JO" 


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