Cobra 29ltd classic : no rx / tx

all functions of the radio are performed by the main IC 2816c . The frequency is controlled by this also and if it is blown you will loose your frequency and the problem that emits is in your statement.

look at a schematic of a 29ltd to do that.. the 25 does'nt have it in there easily.. the 29 can be fixed to change tx/rx freq. with the delta tune

Hi,my name is John. you need to adjust both TR23 & TR21 to 8 volts.......then you should be OK.......good luck. Rate this solution on the four thumbs--up.thanks John.

Try a new Mic. Make sure its a working mic. If you have a bad mic, the receive will not work.

Yes the light will stay on and change when you key the mic

Hello there
Here is the diagram for you
Cobra 29LTD, 29LTD ST, 29WX ST
Documentation Project
CBTricks.com
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29LTD ST Owners Manual
29WX ST Owners Manual
DIAGRAMS
29LTD ST Schematic Diagram
29LTD ST Schematic Diagram
29WX ST Schematic Diagram
WX Schematic Diagram
29LTD, 29LTD ST, 29WX ST Factory Service Manual
Page 1 to 11
Page 12 to 34
29LTD Factory Service Manual
29LTD
29LTD Schematic Diagram
29LTD Schematic Diagram
29 LTD Classic Schematic Diagram (Courtesy of Rick Jackson)



Mic Wiring
Stock
1- Shield
2- Audio
3- Transmit
4- Receive
Astatic (4 wire)
1- Shield
2- White
3- Red
4- Black

Astatic (6 wire)
1- Shield & Blue
2- White
3- Red
4- Black
Yellow NC
Daiwa EM-500
Cobra CA Series
1- Shield & Black
2- Red
3- White
4- Blue
Galaxy DC-521S (4 wire)
1- Shield
2- Yellow
3- Red
4- Black
Galaxy CB-660EI
1- Shield & Black
2- White
3- Red
4- Blue
Sadelta
1- Shield
2- White
3- Brown
4- Green
Turner
1- Shield & Red
2- White
3- Blue
4- Black
Yellow NC

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.

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.

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.