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Yaesu MH-48 microphone

Discussion in 'Microphones, Speakers & Audio Processing' started by KD5PCK, Oct 11, 2010.

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  1. KD5PCK

    KD5PCK Ham Member QRZ Page

    Hello all.
    I am having trouble repairing the wiring on my Yaesu MH-48. I ordered what I thought was a replacement cord off of ebay but it seemd the wiring is not correct. I have found the pinout for the microphone here:
    My problem is that I am trying to figure out the sequence on the microphone end. Does this just go straight through in the same sequence? I have tried that and it doesn't seem to be working. The microphone keys the radio when one of the two buttons on top is pressed, not when the PTT button is pressed. Can anyone tell me the sequence of both ends of the microphone cord? Thanks in advance.
  2. W9GB

    W9GB Ham Member QRZ Page

    Yaesu MH-48A6JA DTMF Microphone for the following Yaesu Transceivers:

    * FTM-350
    * FT-8900
    * FT-8800
    * FT-7900
    * FT-2900
    * FT-1907
    * FT-1900

    Internally, this is the same microphone as the MH-48A6J, except that it has the telephone-type alphabet printed above each numbers (2 - 9). This lettering is to assist with APRSĀ®/Packet use.

    Yaesu MH-48A6JA DTMF hand mic -- Universal Radio


    Yaesu MH-48 microphone - How it Works (Grant, ZL2BK)

    Additional Internet web pages about the MH-48 (All via a simple Google search)

    Last edited: Oct 11, 2010
  3. KD5PCK

    KD5PCK Ham Member QRZ Page

    I am not sure if I worded my original post correctly.
    I know the sequence of the wires on the modular end of the cable, the end that plugs into the radio. What I need to know is the sequence of wires on the end that plugs into the microphone itself. Do these wires run straight through or do they crossover? Thanks.
  4. W9GB

    W9GB Ham Member QRZ Page

    Is the microphone body directly wired to the replacement cable (soldered to the PC board inside microphone case) OR does it have a 6-pin modular plug jack?
    I thought the MH-48 microphone was a directly wired cable with a 6-pin modular plug for radio connection ?!
    Straight-Through is industry Best Practice for microphone cables using modular connectors (6-pin, 8-pin, 10-pin) -- Keep I Simple Sxxxxd (KISS principle).

    A COMMON MISTAKE for DIY modular plug (6-pin and 8-pin) cable connections -- radio amateur actually inverts the entire pin sequence at the other plug by accident.
    Many radio amateurs use UTP/Ethernet jumper cables -- that is not always a good idea -- especially if the cable is not marked (cross over cables to exist).

    The EIA/TIA 568/569 Standard in early 1990s for unsheilded twisted pair (UTP) cabling and connector pin assignments for the 4 twisted pairs varied (568A and 568B) due to previous AT&T cabling standards.
  5. KD5PCK

    KD5PCK Ham Member QRZ Page

    Yes, the cable on the microphone end terminates into a 6 pin modular plug that attaches to the board inside the microphone. I thought the wires would go straight through.
    The cable that I bought had the sequence reversed from the modular plug (radio end) to the microphone end. I tried reversing everything to where the wires feed straight through but it's not working. Am I missing something?
  6. W9GB

    W9GB Ham Member QRZ Page

    FIRST, IF you don't have a VOM or DVM -- get one. You are kidding yourself -- if you are trying to troubleshoot without one to perfrom simple continuity and resistance measurements.

    OK -- that tells you -- by looking at the Universal Radio link (provided earlier)

    -- that the cable is wired incorrectly (backwards likely).
    SEE where PTT (+ VDC) and GND are?
    The PTT button shorts those 2 wires for radio transmission.
    NEVER cut or re-wire connectors -- UNTIL you diagnose the CURRENT state (starting point).
    I will assume you KNOW the microphone is working and NO problems with the microphone body.

    1. Radio cable from eBay not working.

    2. OK, check the continuity of that cable. WHY?
    Modular plugs were originally made for flat cable (telephone) by AT&T.
    It is very easy to "miss" a crimp on a wire (no connection) -- when applying these connectors!!!
    I have found this problem with pre-made cables from Category 6 to DIY cables sold by vendors.

    Your DVM and VOM can accomplish in about 1 minutes of testing all 6 pins -- whether cable is good!

    3. IF the cable is OK --- then attach one end to the radio's microphone input (other end NOT attached to microphone.
    Then check to see that PTT works (radio connected to 50 ohm dummy load) --
    by shorting appropriate pins.
    IF it does NOT -- then you may have a problem with the radio's chassis mounted radio connector or the cable connector is not properly seating to the radio's connector.

    Last edited: Oct 11, 2010
  7. N6VIG

    N6VIG Ham Member QRZ Page

  8. N1BHH

    N1BHH Ham Member QRZ Page

    The connector on the microphone end is not an RJ-type connector, it is a modular type, not the same. If you have a broken cable you can get a replacement cable on ebay. I have an FT-8100R that had a worn out cable, jacket worn through, and I bought a replacement cable for it and it's easy to replace. All Yaesu microphone cables are easily replaced.

    You need to tell us which radio you are using it on to determine which replacement cable to use, because some were wired for the FT-8000, 8100 and others. The rest are wired for others such as the 8800 and 2900. You need to be specific about the radio and the microphone.

    One example on ebay for the 8100 and similar:

    Another example for the 8800 and similar:
  9. KD5PCK

    KD5PCK Ham Member QRZ Page

    I am using the microphone on a 7800 and an 8800. Both cables need replacing.
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