J.C. Penney 981-6248 no squelch

[PoDuck]

I finally decided to look at this pair of 6248's I got from the guy in Cincinnati, and the first one I have on the bench seems in good shape. I have only found two problems. First is the RX light doesn't work. Might be a burned out LED. The bigger problem is that it won't squelch.

I have the Photofact 274 book for this, which is the same as the Sears 934.38310700, and believe it or not, I have one of those Sears radios, so I might be able to do some comparative testing. The Sears radio is having trouble with weak receive, but I don't think that will affect the squelch stuff.

Anyway, I am having a hell of a time finding the squelch circuit in the schematic, and really the only part I know to look for is RT102. Where in the flow would I normally find the squelch circuit? Does anyone have this schematic that can show me the portion I'm looking for?

Thanks.

 

[Dmans]

PoDuck,
I am looking at Sam's 235 on a J.C. Penney 6241 (I know it is a different model from yours but it uses the same PLL as yours). The AM/SSB squelch amp in this model is Q254 (a 2SC458D). RT202 is the AM Squelch range variable and RT252 is the SSB Squelch range variable. It appears that Q254 "samples" from the 2nd mixer for the AM side and from Q252 and Q253 (SSB AGC AMP-a 2SK55E for Q252 and a 2SA844E for Q253) for the SSB side.

I would guess that the 6248 model is similar. I could be wrong!

Hope this helps!
73's
David

 

[PoDuck]

Well, I finally found the squelch circuit, and those numbers are way off. That Q254 was Q108, for example. I've opened up this other radio in the mean time, and when I first turned it on, it was receiving very quiet, and then slowly dropped down to nothing. That suggests to me I have a bad capacitor, so I decided I might as well recap this board. Only found one cap that was way out of tolerance so far. Surprisingly all these caps are Nichicon and Nippon Chemicon from the factory. I'm used to off brand caps in radios.

 

[Robb]

So then - Ill bite - what's the story on those 458's anyway?

EDIT:
Sorry - wrong thread for this question!

 

[PoDuck]

458's?

 

[PoDuck]

Oh, the other thread. They will have to wait until tomorrow.

 

[Dmans]

Good deal PoDuck!
I did find a bad 2SC458 in my little $10.00 Sears 663.3807 recently. It was in the Squelch circuit (TR11 or TR12-can't remember which right now). Replaced it and still no Squelch. Did some digging and found that the leads on my replacement (2SC945 I think I robbed from a 2950) were different from the 458. After reinstalling my replacement "cross-legged" all worked well.

73's
David

 

[357]

damn...458's come back to haunt

 

[nomadradio]

I'm used to off brand caps in radios.

When CB radios were actually made in Japan, the capacitors were, too.

73