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Final transistor replacement

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2006exploder
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Final transistor replacement

#409668

Post by 2006exploder »

Hey everyone, I am trying to fix an old realistic TRC-427 I picked up in a batch of radios. Upon plugging it in, no sound from the speaker, but when I plug in an external speaker I only get a very loud buzzing noise, that is unaffected by adjusting any of the knobs or switches besides pressing the PTT button, which makes the buzzing go away. The MOD light does not illuminate when keying and talking into the mic. also no sound when talking using the PA function with the external speaker plugged into the PA jack. after taking it apart, I see no obvious issues like burnt or melted components, but I am only getting 21 ohm resistance between one leg of the transistor and the ground leg, so I figure it is shorted (i am not sure what the resistance should be, but I figure it should be more than 21 ohms).

The transistor that appears shorted is C2029/1, but I cannot find a replacement for sale online, so I was wondering if anyone knew of an equivalent transistor I could replace it with.

also if you guys have any other components you think I should check, please let me know.

Thanks!
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#409672

Post by MDYoungblood »

If your hearing the buzzing and it goes away when you key the mic it is most likely the wiring for the mic is shorted.

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#409675

Post by 2006exploder »

MDYoungblood wrote: Dec 09 2022, 15:20 If your hearing the buzzing and it goes away when you key the mic it is most likely the wiring for the mic is shorted.

3’s

Greg
Thanks for the advice. do you mean the wiring inside the microphone? or the microphone circuit inside the cb.
thanks
Dylan
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#409695

Post by MDYoungblood »

It could be a little of both, in the past I would change the wiring inside the radio to accommodate a basic Cobra, Uniden, Ranger microphone.
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