Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
I've just finished restoring a Silvertone Model 1908. Reception is good BUT off-station the radio is very noisy (squeals). Once a station is tuned-in, the radio is reasonably quiet. However, tuning is difficult; that is, very narrow "quiet" range requiring very precise, delicate tuning to quiet radio. The squeals seem worse at the high end of the AM band.
Any suggestions would be welcome.
Thanks,
Don
Posts: 7,300
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Sound like your IF amp is oscillating. Try touching the grid cap on the 6K7 and to hear if it clears up. May drop the gain a bit. If so realign the IF transformers if it still persists detune one of the IF trimmers.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
Thanks, I'll try that.
Don
Posts: 2,035
Threads: 367
Joined: Jun 2010
City: Dover, OH
Actually, this sounds like the exact issue my RCA 19K developed. Sounds like it needs the same thing done to it for the problem.
No matter where you go, there you are.
Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
I'm sorry, I am not familiar with what you did for your RCA. Could you elaborate?
Thank you,
Don
Posts: 2,035
Threads: 367
Joined: Jun 2010
City: Dover, OH
I haven't done anything for the problem yet. I was just mentioning that my RCA seems to have the same problem, really noisy between stations and hard to get tuned in just like your Silvertone. So, I am hoping the solution mentioned will work for both of us. 
No matter where you go, there you are.
Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
OK, thanks. Here's hoping.
Posts: 4,875
Threads: 54
Joined: Sep 2008
City: Sandwick, BC, CA
There may also be an issue with the AVC bypass capacitor, it could be open circuit or missing. Another thing to look at are grid caps and grid cap leads, sometimes the solder joints on the grid caps get flaky, as does the solder joint on the clip that goes on it, the wire can also break internally. Another source of oscillation can be the first audio tube, if it is a glass type like a 6Q7G or a 75 they cause a squeal with the shield removed.
Regards
Arran
Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
Thanks, Arran. I'll get into troubleshooting tomorrow. I'll post what I find.
Don
Posts: 95
Threads: 34
Joined: Oct 2016
City: Fountain Hills, Arizona
The AVC bypass cap was in-circuit and correct value per the schematic. However, increasing the bypass cap value quieted the radio substantially. Tuning is now much easier and the audio is cleaner once tuned. The radio now performs as I expect it to.
Thanks for the tips,
Don
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