Question about Cobra 29 LTD CB Radio

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

I'm trying to hook up my spare radio in a different truck while mine is in the shop. The radio is the one that was in my Kenworth when I bought it and it worked fine. I took it out to put in a hotter radio and have kept this for a spare. I am now trying to hook it up in a 2004 Freightliner and the fuse blows out each time I try to plug in the power cord. I'm sure I have the polarity correct

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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

Posted on Feb 23, 2009


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1 Answer

How do i find and replace the finals in a cobra 29ltd classic

The protection diode (a black, tub looking devise) hooked to the positive power wire near the back of the radio, is most likely your problem. Check to see if any doides are shorted by using a Volt/Ohm Meter by checking for a short. For more imformation or help, email me at
"Original Radio Man"

Jan 01, 2013 | Cobra 29 LTD CB Radio

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 .


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

1 Answer

I'm doing a talkback mod on a Cobra 29 LTD. I'm trying to wire it to the on/off channel 9, and I keep getting it turning onn all the time. When the switch is on or off, the talkback is still coming...

If you look at the tabs on the switch. You will have what looks like this.

* *
* *
* *

hook one wire to the center tab of one side. And then hook it to the top tab of the same side.

* *'''''''''''''''
* *'''''''''''''''
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Hope that helps.

Jan 26, 2010 | Cobra 29 LTD CB Radio

2 Answers

Blowing fuses when power is hooked up

once you've done this, hooked up a radio backwards, you have to change the resistor...take it to a shop I only charge $18

Nov 26, 2009 | 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

Blowing fuse

Your polarity protection diode has been blown. If you tried hooking up your CB and accidentally pushed the plug in backwards. Inside the radio, there are 2 big black diodes near the transformers, D8 and D23. Replace these with the same or bigger. You can the burnt one out and the radio will work, but if you hook it up wrong again, it will fry the radio.

May 02, 2009 | Cobra 29 WX NW ST 40-Channels Base CB...

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

2 Answers

Powering up problem.

It,s the mounting the screws are touching something in the radio when bracketed and yes you probably blew the power diode in the radio, it can be fixed pretty easily. Try a fuse on the ground and the hot next time.

Jan 30, 2009 | Cobra 29 LTD CB Radio

1 Answer

Blows fuse.s when i hook up the coax

The polarity is reversed. The red power lead must go to +, the black to -. Most trucks are - ground but yours may be the opposite.

Sep 02, 2008 | Cobra 29 WX NW ST 40-Channels Base CB...

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first check the inline fuse to see if it is still good. If it is'nt, you can tell by the link in the fuse, will be broken and glass will look burnt. I f fuse is good then you can a schematic drawing of your radio and it will show you wher the resistor or diode that is a back up or safty circut for your radio. google cb radio and you will find many useful sites for repair and mods.

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