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Thread: Convert a 4 wire microphone to a 3 wire microphone?

  1. #1
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    Convert a 4 wire microphone to a 3 wire microphone?

    I have a Pierce Simpson Panther SSB CB radio I bought new in the 70's. Over the years the microphone has been misplaced and it requires a 3-wire female plug in order for it to work.
    I have a like new Wilson Trucker 4-wire microphone on hand. Can it be wired to work on a 3-wire plug?
    I've tried a few combinations and it will not modulate.
    Any ideas?
    I do not have a schematic on my Panther radio to see which wire is doing what function with the microphone.

  2. #2
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    I was able to find that the Pierce Simpson microphone was wired:
    Pin 1- White
    Pin 2- Shield & Blue
    Pin 3- Red
    Wires Yellow and Black are not used.
    I cannot find anything on the wiring for the Wilson Trucker ( non-amplified battery powered mic ) for the wiring for a three pin connector.
    Anyone here have any info on this microphone?

  3. #3
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    Absolutely you CAN do that.
    I am sitting here looking at the SAMS CB Photofact on that radio and here is what the radio has:

    pin 1 - mic audio
    pin 2 - radio ground
    pin 3 - relay activation (ground it to transmit, open it to receive)

    THAT is the way that the radio mic socket is wired.

    Most microphones these days have 4 or 5 wires.

    The 4 wires usually have
    mic audio,
    RX,
    TX,
    shared shield

    The 5 wires typically have
    mic audio
    mic shield
    RX
    TX
    switching shield

    with almost any of these mics the switch inside is NORMALLY connecting the shield and RX pin. When you press the switch it opens the RX pin and connects the shield to the TX pin.

    If you can identify that on most any mic you have you are most of the way home.

    IN THE END, you will need to identify the
    mic audio wire, and
    the TX wire

    then find a 3 pin female mic connector and connect the mic audio to pin 1, and the TX wire to pin 3.

    From there it depends on your mic.

    If it is 4 pin you need to find the one shield wire and use that as your ground and connect it to pin 2 on your female mic connector.

    If it is a 5 pin you need to find both the mic audio shield AND the switching shield, wrap them together and connect them both to pin 2 on your female mic connector.

    Any wires left, leave them cleanly cut and tape or otherwise fix them up where they won't get into any trouble and out your mic connector shell the rest of the way together.

    Should be good to go.

    The radio uses relay switching instead of electronic switching like newer radios.

    To make it transmit you have to wire the mic so that, when you press PTT you connect pin 3 to pin 2 and when you let go it reverts to PTT.

    The mic audio line needs to be referenced to the same ground and that is why, on a 5 pin mic, you have to tie the two ground together and connect them BOTH to pin 2. On a 4 wire mic they already ARE the same ground so you don't have to tie any wires together.

    Good luck and, if you have any more questions let me know!

    Bob

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    Thank you for the info.
    I took the microphone apart since I can find no info on it anywhere on the WWW.
    It is a Wilson Trucker Noise Cancelling Microphone ( non-battery powered)
    The wires are:
    shield
    White
    Red
    Black
    Blue
    Yellow
    I wrung out the wires.
    From what I was able to trace they seen to go to here:
    Shield is chassis ground
    White - microphone switch - then to a small transformer or choke coil?
    Red - microphone switch - to the Blue wire when closed
    Black - to Blue wire when switch Open
    Blue - Red when switch closed
    Yellow - is cut off in the cable
    While running the wires I ran into a small Jelly-bean capacitor with a 104 marking. I believe it is a 100nF rating.
    This little capacitor is bad. You cannot charge/read through it on any scale. This may be why I cannot get this microphone to work.
    My concern is I may have blown it out trying to figure how to hook up the microphone wiring.Name:  wire4.JPG
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    Thanks again for your help.
    Rob.

  5. #5
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    Reading what you put in above I am making a guess here...... but I feel fairly sure about it.....

    A couple of things that I am relying on most of the information you passed......

    When the mic button IS NOT PRESSED..... BLUE is connected to BLK AND NOT RED
    When the mic button IS PRESSED..... BLUE is connected to RED AND NOT BLACK

    This makes it sound like in the SWITCHING part of things.....
    BLUE is the common,
    BLK is the RCV wire, and
    RED is the TX wire.

    If that is true then my thinking is that the following will "get you there".....

    1. The WHITE wire is the mic audio line. Solder that to a mic plug's pin 1

    2. The BLUE wire and shield should be tied together and soldered to the mic plug's pin 2

    3. The RED wire should be soldered to the mic plug's pin 3

    IF you WOULD LIKE to be a little more sure.....

    IF you STILL have the mic apart... or if not... you wouldnt mind opening it up again......

    send a photo of the top and bottom surface of that PC board. If I have those pics ALONG WITH the ones you already posted, I might be able to conjure up a drawing of this mic and then BOTH of us would be MORE sure.

    I am pretty sure my suggestion above will do it but, that said, if you COULD give me those two additional pics I would feel a lot better about it!

    Cheers!
    Bob

  6. #6
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    Thanks for the info. I'll do a few clear photos in the AM and post them here.
    Rob

  7. #7
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    Good deal. If you can, get pics of both sides of that board.....and I hope this makes sense..... just flip it in one direction so that the board is in the same general direction. What I need to do is look at both sides of it.....and be able to figure out how the wires and parts on the top (parts side) connect via the traces on the bottom (foil side). If I can do that.... it will be pretty easy.

  8. #8
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    I figured out a way to back light the PC board. I hope this makes it easier to trace the wires.
    I've got new caps coming to replace the dead one.
    Rob.


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  9. #9
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    I think I can. Let me look at it in the morning. The shots look good. Thanks!

  10. #10
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    Let's see if this image thing works here.
    Below, the image has two things... on the top...what I believe to be the schematic. The RED lines are meant to show the PCB copper connections..... the wires are in black with the color written in. The transformer thing... is just a guess. If I had my hands on it... I could measure it and see...but either way.... I think that this is correct enough to work for you.

    The bottom part...shows what I would do. The WHITE wire goes to pin 1, the RED wire goes to Pin3, the audio shield and the blue line wrap together and solder to pin 2.

    If you have any questions, give a shout!

    Bob


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