| Author |
Message |
    
Mike
| | Posted on Sunday, November 24, 2002 - 1:33 am: | 
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I have a Cobra 29LTD. No swing (dead carrier) on transmit. Receives ok. Other transcievers work ok with same existing antenna system. Need some advice. What shall I look for? Do? HElp! Mike |
Karatebutcher
| | Posted on Sunday, November 24, 2002 - 11:46 am: |
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Mike I just looked in my closet, I have a Cobra 29 ltd also, fist check all the switches, make sure they are in the proper position, switch them around a bit, then see if it still does what it is doing, is it grounded ok? |
Jose22
| | Posted on Sunday, November 24, 2002 - 1:50 pm: |
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can others hear you? IF not change mike. Could be short in mike connector. I would start there. |
307
| | Posted on Sunday, November 24, 2002 - 7:32 pm: |
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When you say "DEAD KEY" , do you hear a "squeal" or "hum" when listening on another radio? It sounds to me like the carrier is modulated very steady , giving you the illusion it is dead key.
307 |
Mike
| | Posted on Monday, November 25, 2002 - 12:02 am: |
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Karatebutcher and Tech 307........thanks for the feedback on my Cobra 29LTD no tx. Hooked it backup this eve. Rx is still ok. Mic works ok on a Cobra 21. I have tried other mic's that are good. So, mic is ok. No swing on s-meter on tx or Rx with the 29. Tx light goes on on tx. Rx light always on on Rx. and that is all that is affected. that is all. I briefly key , so as not to over load anything. I turned on a handheld and on same channel. Keyed mic on Cobra 29, No humming, squeal, hisssing, nothing coming thru on handheld. There is no audio coming in tx from Cobra 29 to handheld. Just dead..I checked all swith positions. Ground ok. I suspect someone may have blown the final? Possibly the mic gain switch being bad? Cobra 21LTD works ok with existing antenna, etc. I performed the "wiggle" test throughout the chassis on the 29, on board,soldering joints, wires etc,; no heated parts, caps,bd cracks, etc. Does hot look like anthing has been cut or mod. Other than a repair shop!!!!..... Help |
Mikie
| | Posted on Monday, November 25, 2002 - 11:26 am: |
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Karatebutcher and Tech 307...Correction on my previous message on Cobra 29LTD, no Tx. Tx light indicator DOES NOT turn on on Tx mode. thanks.. |
307
| | Posted on Monday, November 25, 2002 - 9:16 pm: |
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Hmmm. If you can "hear" on it and it does not TX , I would have to guess that either the TX Oscillator died and the PLL shuts down the TX or the TX Inhibit transistor is bad. This is a job for a CB Shop...
307 |
Mike
| | Posted on Friday, December 27, 2002 - 12:44 am: |
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307
On my Cobra 29 LTD, with OK Rx and no Tx this is what was done. After some struggle and researching the problems from several other sources I replaced C112 and C119. They were probably shorted. Hooked up and had Tx but no modulation. Replaced the final (RF power output transistor and bingo! The radio had Rx, Tx with modulation. There are still some minor adjustments to be made, but it sounds ok to the locals. Thanks 307 ....you got me going in the right direction. |
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