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Yaesu FT1500m mic wiring

Discussion in 'Microphones, Speakers & Audio Processing' started by KF4ZGZ, Jul 2, 2016.

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  1. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Hi all!
    So I have an early model 1500m and the mic cord (MH-48 mic) has pretty much disintegrated.
    I am trying to convert an old cb mic with the 6 pole ptt switch with an rj-45 cord to use with the 1500.
    I have an electret element and I can get the rig to key, but no audio out.

    Can anyone help me wire the electret to the 6-pole ptt to the 1500?


  2. W9GB

    W9GB Ham Member QRZ Page

    Matt -
    1.) There are TWO Types of Elecret microphone elements: 2-wire and 3-wire.
    2.) Elecret microphone elements require DC power (has to be wired correctly to avoid damage to radio or microphone).
    SparkFun BOB-12758
    Yaesu FT-1500m Product Page -- Yaesu USA (California)

    Yaesu FT-1500m Operating Manual

    PAGE 6 : Pin assignments for the Radio's MIC connector - 6-pin modular (telephone style)
    Pin 4 - GND
    Pin 5 - AUDIO (+)
    Pin 6 - Push-to-Talk (PTT) Line
    Yaesu MH-48A6JA DTMF Microphone - available at Universal Radio, $54.95

    image.jpeg image.jpeg
    Last edited: Jul 3, 2016
  3. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Yeah, I have seen all of this and wired as all of this says. I've been around radio and google for a good while and found all of this.
    But no stuff for the 6 pole ptt switch.
    At this point I also assume the 1500 needs a 3 wire element? The one I have is 2.
    That in itself may be the whole problem.


  4. W9GB

    W9GB Ham Member QRZ Page

    Regarding the PTT switch, Yaesu used a standard SPST switch, but appears to have changed to a multi-pole unit on later models. Use you DVM/VOM to assure proper operation and what 2 contacts CLOSE when pushed (shown as lower 2 at one pole in a photo).

    Schematics were provided on the back of Radio Shack's $3.00 elecret elements, as noted by W1AEX. No PTT switching of audio line.
    The DC Voltage can come from Pin 3, Vcc, of your FT-1500m mic connector.

    Are you just trying to replace the Yaesu MH-48 microphone element??
    This microphone model was noted for muffled audio.
    Yaesu MH-48 Schematic diagram
    Last edited: Jul 3, 2016
  5. KC8VWM

    KC8VWM Ham Member QRZ Page

    Last edited: Jul 4, 2016
  6. W8AAZ

    W8AAZ Ham Member QRZ Page

    My cord split the vinyl jacket and after it got bad enough to be annoying, I looked on ebay. Saw a lot of Chinese made replacements for cheapish. They are not hard to change. But I saw one seller with a cord that was a better quality than the cheaper ones and upon receipt this was borne out. However I think that seller had only a limited inventory of the high grade cords and is long gone from ebay. Still, it was cheaper to replace the cord than any sort of replacement microphone that was correct for the radio. Guess it is nice to have the correct mic with all the functions, but the programmable functions I use so rarely that I forget how they are programmed. And touchtone? Never since cellphones! I suppose I would go for a substitute mic in the last resort, if it was small and compact and not too cheesy or cheap. Don't want to worry about radio mic failures at a bad time. Sadly I see the modular mic connector as a step towards trouble to gain compactness. Maybe the original US made telephone company versions were a bit better ?
  7. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Thanks for the replies.
    This radio gets little use, hence the "project mic".
    Plus it gives me something to do ......
    I'll pic up a 3 lead element and try it again ..... worst case scenario is cheap mic or cord from the intarwebs.

  8. W9GB

    W9GB Ham Member QRZ Page

    Follow the schematic in post #4 ... and you can make the 2-lead version work.
    REMEMBER: Watch the Polarity of the 2-lead device (it does have Positive/Negative).
  9. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Success! .... kinda ....


    Keyed up, and audio out. Telephone cable with an rj-45 and a gutted cb mic.
    But it's noisy and sounds like crap, lol! BUT IT TALKS!
    Lots of white noise when keyed up and the audio out sounds like a hot-rodded D-104.
    W9GB provided info that is probably spot on, but I'm bored, impatient, and Radio Shack is too far away.
    Using his info I was able to google up an similar, simpler circuit that I could scrounge to components for.

    I used a resistor and a capacitor, hooked to the vcc and ptt to ground.
    I cut a piece of foam to fit the hole for the dynamic element, and stuffed the electret in a hole cut in that.
    I plan on messing around with the keying to see if it will get rid of the noise, and maybe play around with the element placement.

    Any suggestions? And yes, if I get to RS I will get the stuff for the full circuit.

  10. W9GB

    W9GB Ham Member QRZ Page

    FLAT Telephone cable is BAD for Audio ... near RF transmitters.
    The cord acts as an antenna (which you should know, Electromagnetic theory).

    This is the reason microphone cables coiled (or straight) SHIELD the conductors. Heil Wire, sold by Heil Audio is one product specifically for radio amateurs (separates PTT from MIC audio, as well).
    What happen to the Uniden (CB) microphone's original cable?

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