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Cobra 29 no modulation

2FB327

2FB327

Active Member
Oct 31, 2012
270
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Next in the stack of radios from the unknown. Is a 1998 cobra 29 with a KEPL-255 board.
The radio receives and it has a 5 watt carrier but no mod.
I went thru with my FC and have the frequency from the mic pins to the so 239 but no mod with good known mic's.
If I touch pin 4 of the audio chip I get the loud noise, the radio tx/rx light changes when you key and the meter moves. But if you switch to PA and plug in the speaker to the PA jack there is no mod.

So what is the next step in troubleshooting? I found this chart but need some guidance.

upload_2017-2-11_15-30-26.png
 

That's not it, I pulled and tested a bunch of caps in that area, still nothing.
Where does the audio originate? It doesn't make sense, the noise and voltage is there at the audio chip? Where to start?
 
have you verified your mic is good on the audio portion of the mic. . it keys and you hear but no audio out from the way I take it plus no PA. verify the wires on the switch for CB and PA are making good connection plus clean that switch. 1st verify the mic.
 
Swapped and tested mic's, tested ok.
Problem fixed, the radio must have had a channel kit or echo? in it.
I found the yellow wire from the center of the dynamike to w-32 came apart at the heat shrink where they had a splice.
Now I have a test radio to test circuits on the bench.
 
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