KMART 06-31-62 AM/FM Radio #2 - Introduction & Repair - Part 01

KMART 06-31-62 AM/FM Radio #2 - Introduction & Repair - Part 01. Be sure to like, subscribe, comment!
Thanks For Your Support,
VEG
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My Website:
www.vintageelec...
My KZbin Channel:
/ vintageelectronicsgeek

[@VintageElectronicsGeek]

Playlist for KMART radio #1: kzbin.info/www/bejne/o5bHZ396pb9nl9k ~Jack, VEG

[@jameslane4206]

Hi Jack.You did geat in troubleshoting.To me it does not sound like 60 or 120hz hum. I think your audio circuit is oscillating at about 100 to 400 hz.Look at it on your scope.Jimmy

[@VintageElectronicsGeek]

Thank you James! I'm just faking it ya know! :) I will take a peek at the oscillator, I have probed the noise to see what freq and I believe it was 120Hz at the speaker, don't remember now...need to get back to it this week when I have time, thanks for the assist! ~Jack, VEG

[@DERB_Seymour_Indiana]

Hey Jack. It's difficult to hear, but the noise is still there, you've just changed the volume and frequency a bit by reducing the voltage. One thing your experiment did reveal was that the noise seems to be in the audio section and not in the radio itself. I would take Jimmy Lane's advice and check the audio section out with the O scope. :)

[@VintageElectronicsGeek]

Howdy Doug! OK, Ill check it out...I was thinking power supply section, but will investigate the audio section....thanks for the guidance! ~Jack, VEG

[@westelaudio943]

I agree with the others Jack, that ain't no mains hum. It's around 98 cycles and not constant. It's an internal oscillation, likely in the AF section. Maybe check the bypass caps and switches.

[@JCWise-sf9ww]

I have one of these and it works, but the audio is distorted. hooking up a scope to monitor speaker output, it has severe cross over distortion showing on the scope. Push-pull output transistors are way under biased.

[@carolriley9392]

Would you be willing to sell me one? I'm a very serious buyer thank you so much.