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Post by hossfly on Jan 12, 2011 21:52:35 GMT -5
My nephew has a cobra 29 ltd he just brought to me to look at. It powers on but appears to have no Rec've or Transmit. Anything I need to look at (check) first?  ? |
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Jan 13, 2011 8:50:59 GMT -5
My nephew has a cobra 29 ltd he just brought to me to look at. It powers on but appears to have no Rec've or Transmit. Anything I need to look at (check) first? ? Easiest thing to check first is the microphone. Sub it with a known good one. If that doesn't fix it, then you're looking at a whole list of possibilities, from blown audio chips, to bad voltage regulators, to PLL problems. |
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Post by hossfly on Jan 13, 2011 19:00:35 GMT -5
After a quick check today it looks as if the CB/PA switch is bad with it being stuck in the PA position. Once I plugged a spkr into the pa jack I could hear white noise and a distance trucker. Also rec'd feedback in the spkr after keying the mic. Cutting the volume down allowed me to hear myself in the spkr. The switch will slide back and forth but it seems to not breaking and making contac. Will give it a gud check tomorrow (if I can find time).
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Post by adclp on Feb 3, 2011 22:50:04 GMT -5
Hossfly, I have a 29 that does the same thing, powers up but will not tx or rx. Meter doesn't move or anything, it just sits there lit up. I can hear the "click" inside the radio when you key it up. When mine first started it, you could gently tap on the cb and it would kick back in momentarily and you could tx or rx, then it would go out again. Online research I've done, I had one guy say it could be the C112 capacitor. I put a new one in and it still doesn't work. Anybody have any ideas? I'd appreciate any info on this.
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Post by Tombstone (R.I.P.) on Feb 5, 2011 20:07:32 GMT -5
There could be a whole laundry list of possibilities in that unit too as pointed out earlier. The gentle tap on the radio that's making it work suggests loose connections somewhere (obviously). The pa/cb switch that is discussed earlier can be checked too. What I would do is with the covers off of the radio and powered up, gently push on the circuit board and see if the radio receives or transmits. Also, touch the connections to the audio chip, you should hear a hum, that will tell you if the audio circuit is working. It still could have cold solder joints or a poorly connected component. Of course, you want to check the antenna connector and make sure that there's nothing loose there. Can you see the "S" meter moving around like the rig is receiving? There could be bad connections at the mic plug or cord or the mic itself. These are all of the basic tests that I can think of. If none of this helps you then probing, voltage tests, etc. are the next step. As Sandbagger stated, you could have a PLL problem. loose crystal somewhere, regulator problem. Try wiggling all of the components with a non conductive tool. I hope that something that I suggested helps you, let us know.
Tombstone
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Post by adclp on Feb 5, 2011 21:22:31 GMT -5
Thanks for the reply Tombstone. The antenna connection and mic is good. The PA/CB switch is good too. As far as the "S" meter it just sits there dead. I'm gonna try to check the audio chip and check for cold solder joints. I failed to mention earlier that this radio isn't that old. It's the NightWatch, I think it's an '07, that's what stumped me. Never thought I would have any problems yet. It just started it out of the blue and progressively got worse. I have an older 29 LTD Classic with the Delta Tune and all, and it does the same thing. Only difference is you can hear a low noise of static and you can't tap it to make it work. Heck the NightWatch can't be tapped to make it work anymore either. I haven't used the old 29 in a while, but I'm pretty sure it was ok when I took it out of service. I was just wandering if there might be a common denominator between the two, or with the Cobra 29's altogether. Thanks for the help Tombstone.
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