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Cobra 142 Help Transmits Good No Receive Help Please

blake25537

Active Member
Mar 10, 2019
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The radio transmits very well, but I have no receive at all. The meter doesn't even move even keying up another radio in the same room. I checked all the basic things like speaker, mic even change the audio chip still nothing. Can anyone tell me what to check next I'm lost lol. Thank you very much.
 

Um, does the meter move on transmit? If not that suggests it's just mechanically stuck in place that's bad news. The radio's meter can be a troubleshooting tool if it has not yet failed mechanically.

Do you have any history for it? A previous owner who compulsively cranks adjustment slugs in his radios?

First thing to listen for is the squelch "thump". Turn the volume full up, and the ANL switched off in AM mode. Turning the squelch knob from end to end should produce an audible "thump" in the speaker when the squelch circuit activates and deactivates. If you can't hear this, there is an audio problem downstream from where the squelch circuit connects to the receiver audio.

I tend to start with the "Manual Digital Signal Injector". Lay one finger along the shaft of a small screwdriver. Touch the screwdriver tip to the input and output foil traces of the crystal filter with the volume turned up.

If you get raucous noise from one of the filter's pins your problem is upstream from that filter. And if you don't, there is trouble in the receiver's IF section.

Gotta first pin down what does work to zero in on what's broke.

73
 
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I got the radio on a trade yesterday and he knew nothing about it. It's a very clean radio inside n out. The transmit is good n the meter works, but on receive nothing the meter doesn't move at all even if I key up my base in the same room, still nothing. I checked the speaker, speaker jack, mic, changed the meter still nothing. Thanks
 
the squelch works when I turn it up the little static goes off, then turn back down it comes back. No noise on the screwdriver test
 
Does the Squelch control work? You'd head a thunk, to silence or "tik" to silence from the speaker when you operate turn up - the squelch. It will do this, hiss-to-silence-back-to-hiss-when-turned back down, even when no input on the antenna jack.

How far does the control have to be turned? 1/4 turn is about right...even with no signal - Halfway? That may indicate a failed part back by the Detector that is not sending correction to the radios front end of the receiver.
 
Other things to check...

Look for failed parts or burnt - the resistors used can fail and pop open like a fuse.

upload_2021-1-12_21-13-4.png

COBRA_142_385.jpg

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The board may be populated, but if it's missing key parts that got donor-ed to help another radio work...

Well, it can get interesting...
 
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