Question about Cobra 29 LTD CB Radio

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29 Ltd Cobra NO receive audio. - Cobra 29 LTD CB Radio

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  • Master
  • 713 Answers

Hi,This problem is more common in the "older" 2000's but is relatively easy to fix. Look for the collector of TR-23, you should read about 4.5 V with a dead key. If you find that this voltage is not present, check on the opposite side of R-120 resistor for 6.5V. Most likely this voltage will not be present; if this is the case, C18 has shorted and needs to be replaced. This is a 330uf, 10V electrolytic capacitor beside L31. To prevent "future" problems, replace with a 16V unit.


Thanks and take care

Posted on May 28, 2010

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Posted on Jan 02, 2017

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Dodgem250
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SOURCE: Cobra 29 LTD Classic Operations Manual

For the operation manual, go to cobraelec.com or:

http://cobra.com/downloads/manuals/29LTDCLA.PDF


Thanks!
Dodgem

http://dodgem250.angelfire.com

Posted on May 10, 2008

  • 773 Answers

SOURCE: cobra 29 ltd classic antenna calibration ??

Wow. That's not at all a solution to what this guy is asking. And why all the caps??

The one point jm77437 has that is correct is that you do not set the radio, you set the antenna. The rest is blah blah.

Here is how you tune your antenna for you radio. First off it depends on what kind of antenna you have. most fiberglass antennas have a tunable tip to adjust the height of the antenna. Metal whips either have a collar at the base that the whip will either slide up or down in to adjust the height. The other type of metal whip's you have to physically clip to shorten the antenna, you must be careful with this type because once its clipped, that's it. You cannot add what you cut off.

I am going to give this example using a metal whip with an adjustable collar.

First after your radio is hooked up in the vehicle, drive to an open lot. Buildings and other structures can cause extra reflection. turn to channel 1. Flip the meter to CAL. Key the mic without talking. Now turn the CAL knob up until the needle reaches the little upside down triangle all the way to the right marked CAL. Now you have just celebrated your radio for your setup to measure you SWR. Now while still holding the key, flip the meter switch to SWR. The needle will move, and where it stops is your SWR reading. The lower the better. Anything under 1.5 is considered really good. But still, the lower the better.

Make note of what your SWR was on ch 1.

Now flip to channel 40. Repeat the SWR process. You must recalabrate each time you take a reading.

Now like jm77437 said. If your SWR reading is higher on 40 then 1, then your antenna is too long, and you must make it shorter. Loosen the collar and lower the antenna in the collar 1/4 inch at a time. check the swr each time you adjust the antenna.

If your SWR reading is higher on channel 1, then your antenna is too short. You must make your antenna longer. Do this by loossening the collar and pulling the antenna upward in the collar 1/4 inch at a time, again checking the swr each time you adjust the antenna.

What you want to achieve is having the same SWR reading on channel 1 and 40. then you have the best match you are going to get with that antenna.

If your swr is under 1.5 on all channels, you don't need to fuss unless you are a perfectionist. then by all means go ahead.

If your reading is higher then 3, or your ant light comes on, something is really wrong. Make sure your antenna is connected all the way, and the coax is not damaged.

Its important to have an appropriate SWR because if you do not, you are reflecting too much signal back into the radio, and eventually you will burn out your final transistor, and your radio will be toast.

Some tips: make sure you check the swr with the doors and windows shut. Make sure you are in an open lot. Remember to calabrate ecah time you take a reading. If you have had your radio peaked by a radio shop, and they have lowered your dead key, or have done a swing modification, then the meter in your radio will not work when taking an SWR reading and you will have to use an external meter.

Posted on Apr 24, 2009

  • 773 Answers

SOURCE: cobra 29 ltd classic antenna calibration ??

You should not calibrate the antenna before you install it on the car!! the antenna needs to be calibrated on the vehicle that it is going to be on. Type of vehicle, different mounts, and many other variables can change the amount of reflection you will get.

j0hn9999 did a much better job but left some info out.

Take your SWR readings on channel 1, then on channel 40.... NOW, if your SWR is higher on ch 40 then ch 1, then your antenna is too long and it needs to be shortened. Refer to the antenna instructions on how to shorten the antenna.

If your SWR is higher on ch 1 then on ch 40 then your antenna is too short. You must lengthen the antenna. Again refer to your antenna instructions on how to lengthen your antenna.

You must calibrate each time you take a reading.

Make sure your doors and windows are shut when taking a reading

Make sure you are in an open lot when taking a reading as buildings, trees and other structures can cause reflection and give you an inaccurate reading.

If you adjust the length of your antenna on another vehicle and then put it on yours, the SWR will be off. It will need to be tuned again.

An external meter is better then the one in the radio, but will need to be hooked up in the vehicle you have the antenna on.

If you are not running any kind of power, or do not have a swing kit installed, and the radio is stock, the meter in the radio is more then enough to get a correct SWR reading.

Posted on Apr 24, 2009

  • 773 Answers

SOURCE: cobra 29 ltd classic ant light

Your SWR is probably NOT fine. You need to use an external meter if you have had work done to the radio. Especially if you have had a swing mod done to the radio. When you do this, the dead key of the radio is lower then the calibration knob on the radio can adjust for. It will always come up lower then it actually is.

Your radio might have been fine before the work was done on it because it was putting out very little power. Now you are most likely putting out 50 watts or more. Big jump from 4 watts.

When your raise the power in a radio, you will notice more when the antenna is not properly tuned.

In most cases with a stock CB, even when the antenna is not even near tuned, you will get a reading less then 1.5 anyway.

the more power you put out, the more important it is to have a good match.

But an external SWR meter, and check it. be careful if the ANT light is on.

You might also want to check your coax, connections to it, and your antenna for anything wrong.

Posted on Apr 24, 2009

  • 33 Answers

SOURCE: Cobra 29 LTD Bluetooth

You got your radio peaked? Most likely, however, the pot for the antenna warning indicator is VR6. I always check that after peaking a radio.

Posted on Jul 28, 2009

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2 Answers

Cobra 25 soundtracker with nightwatch


plug the external speaker into your PA jack and select the PA switch. If PA works then the audio chip is good. The cobra 29 must have a mic plugged in to get receive audio, You may have a broken wire at the mic connector.

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I have a bare wire (shield),white,red,and blue from mic. What is the correct pin configuration for a cobra 29 night watch


  • Pin 1 = Shield = Shield
  • Pin 2 = White = Audio
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  • Pin 4 = Blue = Receive

Regards, Tony

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On a cobra mike what color wires are transmit,receive, auto ,common


Hi, my name is John. Welcome to FixYa. # 1 is the shield, # 2 is audio- white, #3 is the transmit- red, #4 is the receive- black. Good luck and thanks for choosing FixYa...John

Nov 02, 2010 | Cobra 29 LTD CB Radio

1 Answer

I have a cobra power mic that has no audio output


Sounds like its not wired up right, the audio wire must be off,take the plug apart and check the white wire, re-solder it. here is the wiring, pin1-shield,pin-2audio-(white), pin3-transmit-(red), pin4-receive-(black).....hope this was helpful...

Apr 23, 2010 | Cobra 29 LTD CB Radio

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Receive distortion


Try your tune knob and your clarifier knob.....hope this helps

Mar 12, 2010 | Cobra 29 LTD CB Radio

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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

Sep 08, 2009 | Cobra 29 LTD CB Radio

1 Answer

Have Cobra 29 LTD CB Radio w/ bluetooth. Power comes on. Does not receive or transmit. What's wrong?


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.

Dec 20, 2008 | Cobra 29 LTD CB Radio

1 Answer

No receive cobra 29 ltd classic


Hi and welcome to FixYa,

Initially, pls confirm that there is modulation (transmit audio). The reason I asked is if IC4 (TA7222P) is blown, then the radio would have no audio amplifier which would explain no receive audio. Additionally, the final and pre-final (TR15 & 15) gets is modulated TX+12 through D8 from T1 which in turn is the output of IC4 through C48.

Perhaps a schematic diagram may be of further help.

Good luck and Thank you for using FixYa. Happy Holidays.

Dec 18, 2008 | Cobra 29 LTD CB Radio

1 Answer

I have just bought a cobra 29 ltd classic with a scanner ant and it worked befor on the turck it was on but now that iv installed it on my truck im not able to talk to other nor hear them


sounds like a mic problem if a wire is broken in the mic it will not let you receive or transmit common..or not to common an audio chip...

Aug 17, 2008 | Cobra 29 LTD CB Radio

1 Answer

Low volume and problems with squelch


Check your speaker for a short.

Jul 06, 2008 | Cobra 29 LTD CB Radio

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