Question about Cobra 29 LTD CB Radio

1 Answer

Cobra 29 fuse

Inline fuse

Posted by Anonymous on

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  • Cobra Master
  • 1,795 Answers

2.5 amp

Posted on Dec 22, 2014

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Posted on Jan 02, 2017

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Benimur
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SOURCE: fuse

Hi,

There are only a couple of components that could cause the fuse to blow. They are:
1. Reverse protection diode (D23)
2. filter capacitor (C123)
3. Outputs (TR14 & 15)
4. Audio Amp (IC4)
5. Zener Diodes (D22 & 19)
6. the fuse itself (it should be 2 Amps

Hope this be of help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FIXYA.

Posted on Feb 12, 2008

One Wire
  • 126 Answers

SOURCE: echo on cobra 29

When you purchase an echo board, the instructions come with them.

If you need any help, don't hesitate to email me at rollincbmods@yahoo.com

Dean Pitts
Rollin CBs

Posted on Aug 31, 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: have cobra 29 nw ltd keeps blowing fuses inline

This is an easy fix if you are comfortable soldering.

You must have hooked it up backwards. Big problem when using a cigarette lighter adapter. You have to be careful, if you hook a radio up backwards you blow the polarity protection diode.

  • Go to radio shack and buy an N1004 diode.
  • Open the radio
  • Look towards the back right of the radio for a black diode D23. it will probably look burnt, but not always.
  • Use a soldering wick to remove the solder holding the diode in.
  • Remove it, and replace the diode making sure its going in the same direction as the old on. Strip on the side the triangle is pointing.
  • Solder it in.
  • Test the radio
That should do it.

Make sure you are careful to hook the radio up to power corrctly.

Posted on Nov 20, 2009

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1 Answer

What size inline fuse is in the cobra 29 wt nw


Usually a 3 amp quick acting 3AG fuse---do not use the generic ones from Radio Shack.

If the radio got hooked up backwards look and test for a dead short across the power leads-----there is a diode just inside where the hot lead goes that will be shorted .

SD TECH

Apr 21, 2012 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

Cobra 29 ltd what is diode d11


if dead remove the diode---check for shorts--also just follow with a volt meter from power source thru inline fuse, up to on/off switch--power ( 12 volts) but not on the other lug with switch on means bad switch.

Apr 06, 2012 | Cobra Radio Communications

1 Answer

How do i tell what i blew on my cobra 29ltd it wont trun on and i changed the diode


If no power and have replaced protect diode--check voltage 12 volts from source thru inline fuse, to inside radio up to the switch---if power (rear two lugs of switch) on one side but not the other with turned on--bad switch is possible.

Apr 06, 2012 | Cobra 29 LTD CB Radio

1 Answer

Just bought a workman 3000 to 7500 watt cb antenna, ever heard of it?? Im going to hook it up at work monday, got a cobra 29 ltd + or - 30 watt output. 9' coax. the antenna has 8" of swr adjustment... for...


cobra 29 has a 12 watt final, doubt you will be doing 30 watts. 25 if your lucky. Use 18 feet of coax, you will get better broad band.

If the antenna comes with the whip in it already, its been tuned at the factory and you shouldn't change it yet.

If not, half way is okay. It still needs to be tuned on a meter. either the one in the radio or an inline.

Mar 06, 2010 | Cobra 29 LTD CB Radio

1 Answer

Have cobra 29 nw ltd keeps blowing fuses inline and in cigarette lighter adapter adapter is 10 amps and inline is no more than 5 amps


This is an easy fix if you are comfortable soldering.

You must have hooked it up backwards. Big problem when using a cigarette lighter adapter. You have to be careful, if you hook a radio up backwards you blow the polarity protection diode.

  • Go to radio shack and buy an N1004 diode.
  • Open the radio
  • Look towards the back right of the radio for a black diode D23. it will probably look burnt, but not always.
  • Use a soldering wick to remove the solder holding the diode in.
  • Remove it, and replace the diode making sure its going in the same direction as the old on. Strip on the side the triangle is pointing.
  • Solder it in.
  • Test the radio
That should do it.

Make sure you are careful to hook the radio up to power corrctly.

Nov 14, 2009 | Cobra 29 LTD CB Radio

1 Answer

Hello there My cobra 29 ltd just went dead what do i need to do to fix it i am not real good with these radios best regards righard


Hello there
If you remove the screws that hold the top cover on
and remove the cover look by the front of the unit and you will see a small inline glass fuse (50x250) .
simply remove this fuse and replace it with a new one
also check all of the other fuses that is going to the power cord too ok
I hope that this has helped you out a lot
best regards michael

Nov 13, 2009 | Cobra 29 LTD CB Radio

1 Answer

Tried to used CB without antena


If you were trying to transmit without the ant. then your assumption about the demise of your radio is correct.If you hooked it up using an inline fuse ,then just change the fuse. If you hooked up without a fuse, then no, you can not fix it. Please rate this answer.

Apr 09, 2009 | Cobra 29 LTD CB Radio

1 Answer

Trying to hook up a cobra 29 but keep blowing inline fuse


I had the same problem with a 25 that was just disconnected for replacement. I found a shorted diode right where the power cord came in. I also didn't like the way the electrolytic capacitor right next to it was charging so I changed it also.
Problem solved.
I am sure the 29 will have a similar setup. I you want I will look up my schematicof a 29 and tell you the numbers to check.
Of course it is also possible somehow too much voltage was applied to the radio. In which case the previous repairs will almost surely be needed.
I hope this helped, Good luck
tdill49

Feb 22, 2009 | Cobra 29 LTD CB Radio

1 Answer

No power at radio, both inline, and lighter plug fuses good,


I had one do the same thing had to replace the +and- wires just inside the case and a capacitor, the top should be broken on the top of the capacitor or maybe just bowed up it was a 1000uF. Pull the cover with the speaker and you will be able to see the problem.

Nov 25, 2008 | Cobra 29 LTD CB Radio

1 Answer

Diode or not


The first thing to check is the inline fuse. If it is blown and a new one does the same, you may have a shorted reverse polarity diode across the power input. If you need further information on how to check and replace it let me know.

Oct 04, 2008 | Cobra 29 LTD CB Radio

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