Question about Cobra 25 LTD 40-Channels Base CB Radio

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No sound Cobra 25 LTD Classic. I have power to unit. The mic keys high just not sound.

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Re: No sound

The Cobra 25 requires the mic to be working for any sound to come out. My suggestion is that you first try a new mic. If this doesn't work, look real close at the board on the soldered side ( around the if section, thats the area that right under the waxed area on the component side of the board ) for cold solder joints ( broken lead solder) You may need a magnifing glass. Good Luck
NC Electronic
Mills, Wyoming

Posted on Jan 08, 2008

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1 Answer

How do i adjust dead key on a cobra 25 ltd classic cb

The only "adjustment" is the AM POWER trimmer. Lowering this will lower your dead key but will also lower your "swing" power. the TX circuit must be modified to lower the dead key and maintain full output. there are many articles on the web for such modification.

Apr 12, 2013 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Its a cobra 25ltd when i key the mike sometimes it hangs keyed up and does it with defferent mikes so the mike is not my problem.

take some electrical spray cleaner and lightly spray the inside of the radio where the mic plugs in. could also be a keying diode.

Jan 04, 2013 | Cobra 25 LTD 40-channel Classic CB Radio...

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Cobra 29 ltd Classic no sound, no rx, all lights work rx,tx, lite up. The SWR meter moves when mic is keyed up.

Check speaker and plug external one in if you have it.

swap mic could be a broke wire or bad switch in handset.

check antenna and coax connections.

i know checks sound basic but they could save you a lot of headaches later

May 31, 2011 | Cobra 29 LTD CB Radio

1 Answer

29 ltd classic wont transmit

Great radio when it works.
If you have your settings on CB - not PA - -be sure that your Cobra has that setting selected.
If CB -is selected and still nothing - be sure you have a working mic. These wires are fragile and can break internally. One easy way to check is to borrow a cobra mic or even drop by a CB repair shop and ask them to do a mic check with the mic - it is free.

If you have a bad mic replace it and all should be well.
If your mic is good and it still doesn't transmit you will need to replace the finals in the unit. It is common that these burn out of you got too close to someone with too powerful a radio. The CB shop will need to look at it further and repairs should not be over about 40.00.

Good luck with your Cobra.

Mar 31, 2010 | Cobra 29 LTD CB Radio

1 Answer

COBRA 25 LTD spikes without keying mike

buy a different cobra 25 4 pin mic and try that . If that doesn't work than you inherited a piece of junk .

Jul 29, 2009 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer


1 Shield 2 White 3 Red 4 Black if the radio keys up as soon as you turn it on reverse 3 and 4 I am not familiar with that mic.But the way I actually should have given you the wiring order is as follows:1Shield 2 Modulation 3 and 4 key up I hope this helps.

Feb 18, 2009 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Cobra 25 ltd wx classic

the mics on these cobras have a receive wire in them so the transmit will still work even if the receive wire is broken,if this wire is broken the unit will not make any sound...........remove the plug from the radio end of the mic and check the connections on the 5 pin connector.....(could be a cold solder or broken wire) or try a new mic or one that is proven work on another radio
hope this helps.................good luck!

Dec 18, 2008 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Cant transmit

Hello Darren, Yes it sounds like the mic is wired bass ackwards,,! A cobra 25 mic wiring is
PIN #1- Shield or ground wire
PIN#2- Audio or Transmit modulation
PIN #3- Transmit or Dead Key
PIN #4- Receive Audio.
When your keying the mic, the RX wires are being connected to make the RX work,,,
*** Let me know how you get along with it. Either buy a new mic wired for your radio or you or someone comfortable with soldering needs to resolder the correct wires back on the mic plug,,,Like I said, let me know and have a great day,, Mechanic is back quiet!

Oct 21, 2008 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

No sound

Yes It sounds as though the audio amp may have taken the hit go to this link and download the service manual it will give you voltage info ...Chia
P.S. If you have an external speaker plug it in to the PA hole on the back put the radio on PA and see if you get any sound then if the dynamike is turned up it will be LOUD.If not I would replace the audio amp.If you need one let me know and ill directc you in the right direction...Chia

Jan 10, 2008 | CB Radios

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