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Mic wiring problems.

I installed a Maxon MCB40 in my jeep but lost the orignal mic for it. My friend gave me a Cobra CA73 mic and when its plugged in all I get is humming and clicking. I think the pins are different for both of them. I have the cover off the cb and the end off the mic but dont have a clue where to swap the wires to. Can someone help me out. Thanks

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  • twfisk Apr 15, 2009

    I have a Cobra CA73 Mic. I need the replacement switch, but cannot

    get this from Cobra. Any suggestions?


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  • 86 Answers

I have one for a Cobra CA50 may work
pin-1 shield or ground
pin-2 audio lead
pin-3 tx
pin-4 rx
there are one more
pin-2 audio
pin-4 -tx

Posted on Sep 16, 2009

  • LB 163 Sep 06, 2010

    For the Audiovox/Maxon MCB-40 the mic wiring for a 4 pin Midland Radio is the correct style pinout to use


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1 Answer

I have a 18 WX ST Cobra CB Radio and when I turn it on, it hums constantly, . Then when I unplug the microphone, it stops. When I plug it back in , it starts again. Any ideas why it does this?

Sounds like the mic plug or inlet is bad,could be a bad mic or plug wired wrong.Try, if you can,a different mic that you know works for your model,if this also fails,a qualified tech is going to be needed to repair.I will suggest one thing you can try,if your confident enough, is where the mic plug goes into the radio there are four or five pins,look closely at the pins and you will see they have slots on the top of them, with the radio power disconnected,not just turned off,try spreading the slots open slightly with a precision slotted screwdriver or small object that will accomplish this,don't use a wood toothpick,it could break off in the pin.Now plug the mic in and tighten it down,reconnect power and see if this solves problem..Good luck

Aug 19, 2011 | Cobra Radio Communications

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Cobra 29 has a 5 tone roger beep . It works fine with a stock Mic . But when I use a d104 I get about a 2 second hum instead of the beep.Any ideas on what is causing this. Thanks

The d104 is a power mic. For what you have explained you have something gone array in your mic or the mic plug. The fact the d104 is a power mic should not make anything hum. With a lot of power behind your CB and the power mic things can sequel with the mic gain turned to high. But a hum is more than likely a bad mic. Try another one. The same kind of mic should be fine.

Jan 24, 2011 | Cobra Radio Communications

1 Answer

Any one got mic wiring diagram

Hi,my name is John. Welcome to FixYa. I,am not to sure, but as I remember this is the same wiring as the Cobra stock mike. #1- shield, #2- white, #3- red, #4- black. Thanks for choosing FixYa...good luck....John

Oct 26, 2010 | Maxon MCB-30 40-Channels Base CB Radio

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My radio recieves ok but only whistles when i key the mike is this a major fix?

Do you have talkback installed? It my be too loud and causing feed back. Back the mic gain down if so.

Could also be improper mic wiring. If you use a mic that is wired for a different radio, it could just cause a hum, buzz or squeal.

Another thing that can cause a hum, buzz or squeal is a faulty volume and or squelch knob depending on the radio.

  • Turn down or disable talk back.
  • If you cannot turn off or disable talk back, lower mic gain.
  • Try a different mic that you know is wired for cobra.
  • Play with volume and squelch knobs while TX and see if it stops at all. If it does replace knob.

Oct 12, 2010 | Cobra 150 GTL DX Base CB Radio

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Hello there, I have the maxon mcb 30 and I have lost the mic. Do you know what kind of mic I must use to work good?

Try the stock mic from cobra, the regular 4 pin mic, its a great mic..... enjoy.... hope this helps....

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Feedback problems with astatic echo boards

This is a classic indication of a lost shield or ground connection in the mic circuitry. Double check these connections for good contact in the mic *and* the plug at the other end of the cable.

Check the grounding and SWR or "match"of the antenna system, too. A poor SWR (greater than 1.5:1 or 2.0:1) can cause the reflection of RF back to the radio. Modifications can increase sensitivity of the mic to this unwanted RF.

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Earphone/mic for Maxon 27MCB radio

I recall the combo unit as I used to sell them. I am about sure they are no longer avaidable. You never know, you might see something on ebay/auction sights that might be to your liking. Good Luck.
NC Electronic
Mills, Wyoming

Jan 06, 2008 | Maxon MCB-30 40-Channels Base CB Radio

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