Question about Cobra 29 LTD CB Radio

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I have a cobra 29 LTD that has no audio in the PA mode or the CB (transmit or recieve) mode i've changed mics and also changed the audio IC to no avail. where do i look now?

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  • Cobra Master
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Look into buying a new radio. If you had researched further you would have found out that unless you are on cb your radio will not operate . If you are on PA the you can only transmit through the PA system not the cb. If you changed the audio IC then you probably did a cold solder on it. You need an external speaker to operate the pa mode and an external speaker to operate the CB mode .If you decide to fix it more it will cost you more then buying a new radio.

Posted on Feb 15, 2015

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Posted on Jan 02, 2017

  • 14 Answers

SOURCE: Have Cobra 29 LTD CB

Sounds like the PLL circuit....... no channel synthesizer will kill the transmit and receive...... bad crystal or IC could be at fault or if someone has attempted to add more channels could also be cause.

Posted on Dec 22, 2008

  • 200 Answers

SOURCE: cobra 29 nw ltd won't transmit

Have you cracked the radio open yet?  check for loose connections etc.  get back to me if that doesnt yeild any results

Posted on Jan 22, 2009

  • 773 Answers

SOURCE: cobra 29 ltd classic cb not transmitting

Check the ground. Make sure its grounded well on bare metal. To see if the ground is bad, or not making good connection, disconnect the antenna and turn it on. if it does not power up, that means your ground is bad, and it was grounding only through the antenna.

Make sure not to key up with out the antenna connected.

Posted on Feb 08, 2009

  • 86 Answers

SOURCE: when i click the mic i get no transmit

If the receive works ok,sounds like a mic
problem,try another mic if you can find a
buddy who has a Cobra that may let you
try it most all Cobra mic will work but not all.
Good Luck

Posted on Sep 12, 2009

  • 773 Answers

SOURCE: 29 cobra ltd c.b. wont transmit or receive

make sure the RF gain is all the way up, and the dynamic is all the way up or most of the way up.

When you say the antenna is good, have you checked the SWR's and or have tuned the antenna to be the correct length for the radio? If this has not been done ever, your radio could be a brick.

Also, make sure the PA/CB switch is on CB. if its on PA(public address) it will not receive or transmit because it is on PA mode, which if you have one hooked up, a PA speaker, then you can talk to people through it out side your car.

Also, make sure the S/RF SWR CAL switch, its the first one on the left, is all the way up on S/RF. this is your signal/ receive setting for the meter. When you hold the key, does this needle swing forward? As well does the RX/TX light turn red? If it does, then the radio is transmitting.

There is another light on the radio under the TX/RX light. It is the Antenna warning light. If this light comes on when you transmit, or has come on all the time during transmit, and now it doesn't then the radio is a brick. That is a warning light. It means that the antenna is not matched, or has not been tuned to the radio. If this has not been done ever, you have killed the radio.

Here is why. When you transmit, you are sending off a radio wave. This radio wave, at 27mhz, is about 36 feet long. In order for the wave to radiate off the antenna, the length of the antenna has to match the length of the radio wave. Now it does not have to be a full 36 feet. It can be an exact multiple of 36 feet. In other words it can be 1/4( one quarter) or 5/8(five eights) of a wave in length. 1/4 of a wave is 108 inches, or 9 feet long. Your antenna is still probably does not seem 9 feet long, but there is usually a loading coil that is not exposed making up the rest of the length of antenna, so that it matches the length of the radio waves electrically. If you were to stretch the coil out with the antenna whip, it would be 9 feet long.

When the antenna does not match the wave length, part of the RF energy does not leave the antenna, and goes back down the feed line(coax) and hits the transmit transistor. Prolonged reflection to the transmit transistor, otherwise known as the final will blow it out. As well depending on how bad the length was off, the more off, the more reflect energy, the more RF energy you are blasting back into the radio, and this causes more things then just the transmit to blow out. Some time the receive goes along with it when it finally goes.

So if the RF gain is up all the way, which by the way is basically how much receive you have, and there really is no reason to have it down at all, and the CB/PA switch is on CB and the needle does not swing forward when its on the S/RF setting, chances are that the radio is now no good.

It is fixable, but if there are no CB shops near you then you will have to send it out. And Cobra will not cover this under warranty because its stated in their warranty that they do not cover damage due to high SWR.

Posted on Apr 06, 2010

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1 Answer

Cobra 29XLR has no receive, no transmit, and meter light goes out when the mic is keyed.


If the PA works then the audio amp is fine. but normally when the one of the lights go out its a shorted capacitor.

Oct 22, 2011 | Cobra 29 LTD CB Radio

1 Answer

Cobra 25 ltd will not transmit it will on pa mode and it recieves i replaced the final pll chip audio chip.can you help


there is the problem. a $150 repair bill for a $ 25.00 problem. After you put in this new IC did you put it on a scope to check it out.How about a frequency counter to make sure you were on the right frequency? take it to a tech and let him fix it .

Oct 16, 2011 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Cobra 29, no rx, no tx, pa dose not work, good mic, good ext. speaker, mic. gain all the way up, and you can see meter in face neddle moveing it rec. just no audio at alland no modulation.


Not sure which model you have as there are at least 13 cobra 29's. I am using the LTD as an example. You say good mic? Is it made for this model? If it is good then I would have to say the final audio stage is not working. The TA72222AP is the IC that is the final audio amplifier. Check pin 1 of the TA72222AP ic for 12 volts. If 12 volts is present then replace the audio IC TA72222AP. If 12 volts is not present then you have power supply problems that are internal. The conclusion I have made is based on no rx audio, ( could have been the jack at the pa and ext spkr) but you say they don't work either, also no meter movement during modulation check (that does not need a spkr to make the meter move) so yes I'm 99.99% sure its the final audio stage is a bad. If your model is not the LTD then the IC could be different but still the same audio final is bad. Replace the part which should be fairly inexpensive. If it uses a metal heat sink be sure to apply heat sink grease when installing new part.

Feb 26, 2011 | Cobra 29 LTD CB Radio

1 Answer

Cb has power but no squelch,can't recieve or transmit


Begin with
  • Volume knob 12 o'clock position
  • Squelch knob full counter clockwise
  • RF gain knob full clockwise
  • Pa/CB switch to CB
  • Mic plugged in
  • Check coax and antenna connections.
  • Make sure your antenna gommet/insulator is installed correctly or it will directed gound. Treat antenna shaft as it is the positive portion of circuit.
If you have another CB check the antenna system with that rig. To verify it is a radio issue. Then dig deeper Microphone, PLL chip, Audio chip etc.

Jan 11, 2011 | Cobra 29 LTD CB Radio

1 Answer

29 nw LTD no audio on receive out the speaker in the radio or through the ext speaker and on transmit no audio.Radio shows a 4 watt dead key


If you take your external speaker and plug it into your PA jack in the back and key up your mic do you hear anything. If so then its not your IC chip if not its your IC chip and it will need to be replaced.

May 14, 2010 | Cobra 29 LTD CB Radio

1 Answer

29 ltd classic wont transmit


Hi,
Great radio when it works.
If you have your settings on CB - not PA - -be sure that your Cobra has that setting selected.
If CB -is selected and still nothing - be sure you have a working mic. These wires are fragile and can break internally. One easy way to check is to borrow a cobra mic or even drop by a CB repair shop and ask them to do a mic check with the mic - it is free.

If you have a bad mic replace it and all should be well.
If your mic is good and it still doesn't transmit you will need to replace the finals in the unit. It is common that these burn out of you got too close to someone with too powerful a radio. The CB shop will need to look at it further and repairs should not be over about 40.00.

Good luck with your Cobra.

Mar 31, 2010 | Cobra 29 LTD CB Radio

2 Answers

I got a cobra nw ltd 29 and as soon as mic is connected it starts making like a thumping sound and thats all it does pa doesnt work and it only sends thumping to other radios


Hi there,

It sounds like a microphone problem! I am a C.B. & Ham radio Tech. Try changing the microphone to another one and make sure the Microphone is the right one for the radio. If the microphone is not the right one for the radio it will not work right or when you plug it in it will automatically key up and transmit and the red TX light will come on and it will try to transmit somthing and that would be the thumping everyone hears!! Try that first and let me know if you have any other questions then you can E-mail me at bigdscbshop@hughes.net

Dennis

Aug 21, 2009 | Cobra 29 LTD CB Radio

1 Answer

Mic wiring for a cobra 85 base cb


Pin 1 is shield, thats the bare wire wrapped around the mic audio wire
pin 2 ic mic audio [usually white)
pin 3 is transmit or push to talk usually red
pin 4 is recieve or speaker complete usually black

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