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Cobra 29 LTD Squelch Modification | Radioaficion Ham Radio

Cobra 29 LTD Squelch Modification


CB Radio Cobra 29 LTD Squelch Modification / Fix

(also applies to the Cobra 29 GTL)

Disclaimer: We are not responsible for what you do to your radio, any damages it may incur during any modifications you perform, any information from this site, or any projects you decide or attempt to build. With that said, perform any modifications or projects at your own risk.

This simple modification fixes or greatly improves the Noisy Squelch threshold problem found in many Cobra 29 LTD CB radios. Older models as well as newer models! The best part is it only requires ONE part added to the radio! It is a low cost part as well!

Problem Description:

The problem with the Cobra 29 squelch is when you set it to where the noise just goes away (the threshold), there is still a muffled up static sound slightly heard from the speaker (in some radios worse then others), you can turn the squelch higher to get rid of the noise, but weak stations that you would normally be able to hear are no longer able to break the squelch. This modification fixes that! If you choose the correct value capacitor for your severity of noise, the noise is usually eliminated completely & the squelch works 100% as it should!

Parts List for MOD:

(Qty-1) 0.1uf (104) 50-volt to 1uf (105) 50-volt ceramic capacitor (see below for details on capacitor value) NOTE on Capacitor: If your noise is really bad the 1uf ceramic capacitor (which has the numbers 105 on it) should be used.

If the noise is there, but not too bad a 0.1uf ceramic capacitor (which has the numbers 104 on it) should do the trick.

In most cases the higher value 1uf (105) capacitor eliminates the noise in virtually all radios. But in most radios a (104) is sufficient. If you try a 104 & the noise is reduced but not quite gone, changing to the 105 should completely eliminate it. In very minor cases, even a 103 (0.01uf) ceramic capacitor will remove the noise.

Modification Instructions:

1.) Remove the top & bottom covers of your radio. (unhook the antenna if connected & unplug the 13.8VDC power cord from the radio)

2.) Looking at the component side of the board (speaker side) locate TR12. (TR12 is circled in GREEN)

3.) Now on the solder side of the board, Solder one end of the 104 or 105 capacitor to the middle leg (pin-2) of TR12. (The solder location is circled in RED)

4.) Solder the other end of the 104 or 105 capacitor to pin-3 of TR12 which is the leg towards the front of the radio.

5.) Check your work to make sure the MOD was performed correctly & be sure you did not create any solder bridges.

6.) If everything looks good & you are confident you did it right, put the top & bottom covers on the radio, hookup the antenna, reconnect it to power & test the squelch for proper operation. The squelch should now work like it should, or the noise will at least be greatly reduced.

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