CB radio channel selection works as if by magic - does anyone have any advice for me?

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El-Dracho

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Bjoern
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Hello overlanders,

Beside my HAM radio I have installed an ALAN Midland 121 CB radio for a long time and am very satisfied with it for trail communication and for drive in the column The device has channel selection buttons (up / down) directly on the microphone. For some time now I have been observing that sometimes - not always - the channels start to adjust as if by magic. If I unplug the microphone, it stops. So the problem is somewhere here.
I have already treated the connection with contact spray etc, without success.
Interestingly, the channels also change when I touch the pins of the microphone socket with my fingers.

Does anyone have any advice on where to look, please? Thank you!

Bjoern
 

El-Dracho

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You are connecting the two pins that control the channel selection, your finger is acting as the switch completing the circuit.
Ah ok, understand... finger switch :sunglasses: So I will check the channel change buttons at the mike or replace it. It's always great to see how quickly you can find good help here in the community. Thank you.
 

Greg Eigsti

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Is there any kind of lockout on the mic that disables all mic buttons temporarily? The (ham) mic in my truck has such a switch and I wonder if that might help isolate/prove where the fault is. If I were at the point that I was considering a new mic I would feel emboldened to tear into the broken one to fix it and/or learn. If you wanted to forego the channel change buttons on the mic you might disable them with a quick snip or two. Maybe.

My initial thought is that a finger touching the mic socket should not provide enough "conductivity" to cause a channel change. May be fine but sounds odd to this non electrical engineer ;)
 
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El-Dracho

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Is there any kind of lockout on the mic that disables all mic buttons temporarily? The (ham) mic in my truck has such a switch and I wonder if that might help isolate/prove where the fault is. If I were at the point that I was considering a new mic I would feel emboldened to tear into the broken one to fix it and/or learn. If you wanted to forego the channel change buttons on the mic you might disable them with a quick snip or two. Maybe.
Thanks! I have the lock button at the HAM mike, but not at the CB mike. I will order a new one now as the old one is quite bulky anyway. will open the old one then as suggested to see what´s going on there! I will let you know...
 
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El-Dracho

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Got the new mike today and just tried it. Unfortunately, the problem ist still there, even with new new mike. And now the problem is even there when the mike is unplugged. Does anyone has an idea? Happy about any advise! Thank you!
 

Greg Eigsti

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Maybe take the radio apart, clean it and inspect for bad solder/connections? Seems weird to me that it previously changed channels just by touching the pins on the jack. Gremlins? :)
 
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El-Dracho

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Maybe take the radio apart, clean it and inspect for bad solder/connections? Seems weird to me that it previously changed channels just by touching the pins on the jack. Gremlins? :)

Contact Midland for technical advice. They might hook you up.
Thanks guys. Have just shoot them a message. Let´s wait for their advise.

Maybe it´s a Halloween thing - haha.
 

El-Dracho

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No reply from Midland support team so far.
But took the radio apart with the help of an experienced radio amateur today.
A few pins re-soldered, cleaned the circuit boards and finally took apart the whole front with the keys and display and cleaned it also. Problem seems to be solved now. Keep fingers crossed.

Thanks for all the advises here!
 
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El-Dracho

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The radio is working. So all good now. Nearly. The radio works with the old original mike, but not properly with the new one. As said I bought an original Midland mike MR120 and would like to use that as it is not so bulky as the omne which came with the radio years ago.

The new MR120 seems to have another pin assignemt despite the product description says it fits my radio. However, do not want to sent it back as transportation is not in relation to the overall price of the mike and I guess, such a 6 pin mike is no rocket science or is it?

So UP and DOWN buttons are not working correctly. DOWN button puts the channels up and UP button is not working at all.

Already checked the pin assignemt with a multimeter and it turned out that DOWN connects PIN 5 and 4 which is the other way round with the original mike. So no big deal. But UP does nothing.

Searched for a pin assignment plan on the web already but found nothing. Any hints, tips n tricks or advise welcome! Thanks, guys!
 

Flipper

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Check the screws on the corners of the circuit boards and make sure they are screwed tight to the metal chassis. Make sure all the ribbon cables are seated correctly from the front panel board to the main board. WWW.WalcottRadio.com has the pin outs for the mic. Might be a system control issue with a bad ground.
 
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El-Dracho

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Check the screws on the corners of the circuit boards and make sure they are screwed tight to the metal chassis. Make sure all the ribbon cables are seated correctly from the front panel board to the main board. WWW.WalcottRadio.com has the pin outs for the mic. Might be a system control issue with a bad ground.
Thanks. The radio is working perfectly, everything fixed. It is just a problem with the NEW mike.
 

M Rose

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The radio is working. So all good now. Nearly. The radio works with the old original mike, but not properly with the new one. As said I bought an original Midland mike MR120 and would like to use that as it is not so bulky as the omne which came with the radio years ago.

The new MR120 seems to have another pin assignemt despite the product description says it fits my radio. However, do not want to sent it back as transportation is not in relation to the overall price of the mike and I guess, such a 6 pin mike is no rocket science or is it?

So UP and DOWN buttons are not working correctly. DOWN button puts the channels up and UP button is not working at all.

Already checked the pin assignemt with a multimeter and it turned out that DOWN connects PIN 5 and 4 which is the other way round with the original mike. So no big deal. But UP does nothing.

Searched for a pin assignment plan on the web already but found nothing. Any hints, tips n tricks or advise welcome! Thanks, guys!
A quick search shows that the Up/Down buttons don’t work on the Midland 120:


MIDLAND ALAN MR 120 CB RADIO MICROPHONE 48 78+ 121 220 6 PIN
ORIGINAL MICROPHONE FOR CB RADIOS ALAN SERIES 48, 78, 121 AND 220. FOR MIDLAND ALAN MODEL 121 MICROPHONE DOES NOT SUPPORT THE CHANNEL DOWN.
 

El-Dracho

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Thanks, Michael! Did also some google research but did not find that. And many product description state that it works with the Alan Midland 121 but do not mention that the up down is not supported. So I will contact the shop and give it back!

Thanks again!
 
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