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Thread: ICOM IC HM10 mic schematic-pc board pic

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  1. #1

    Default ICOM IC HM10 mic schematic-pc board pic

    Does anyone have the schematic and pictures of the PC board for the ICOM
    handheld microphone? I need to rewire one that I received with a 730 rig.
    I have the pinout for the connector but only 3 wires were connected when I received it.
    Also I cannot find the PTT contacts on the PC board...
    Thanks for any help!

  2. #2


    Since nobody has answered this one, if you can't find a schematic or service data, it isn't all that hard to find the PTT switch inside the mic and trace the printed circuit board back to where the cable hooks up for each connection.

    The ohmmeter or continuity checker should be used to make good and sure that the points you trace from the typical microswitch PTT switch solder connects and the cable connects are what you think they are.

    Sometimes the microswitch is only wired as a Normally Open Single Pole Switch, so we are only talking two connections that will close when the PTT switch is activated. Again the continuity checker or ohmmeter will show this closure. In other cases it might be a situation where there are three wires from the switch, the Normally Open contact plus the Normally Closed contact plus the Center, which is switched back and forth. Take a hard look at the little microswitch as these contacts are often labeled on the switch itself as NO, NC and Common.


  3. #3


    Icom microphone listing

    Your Icom IC-730 was factory shipped with the Icom HM-7 hand microphone. See page 3 of your Icom IC-730 manual.
    The schematic diagrams for the HM-7 and SM-5 microphones are on Page 4 of the IC-730 Owner's Manual.

    The Icom HM-10 was designed and sold (option) to work with these Icom radios: 25A, 251A, 255A, 260, 290A/H, 451, 490, 730
    It has an 8-PIN "Foster" circular mic connector and uses a DYNAMIC microphone element.
    Photo is attached

    As you can see from the attached photo, this microphone is a bit complex (PC board inside).
    The imporant thing is to FOCUS on the basic FIRST. Microphone Audio and PTT function.
    This will use 3 or 4 wires (IF the grounds are shared between the MIc and PTT functions)

    THEN move on to UP/DOWN and Scanning functions.
    The Icom IC-730 Owner's Manual will have the mic connector PIN usage/function -- that you can trace (VOM/DVM using continuity function) --
    to wires inside the microhone case (and to PC board). One may be +8 VDC to power and transsistors or other active electornic device inside.

    ICOM is the only Eastern Asia manufacturer that provides ALL of their product manuals (radio and accessory) for download
    by radio amateurs via the Internet -- FREE (no memberships, fees or other such nonsense).

    IF the manual you need is NOT shown, a simple request on their contact sheet will produce a scanned PDF from their paper document library
    within a week (4 to 5 business days).

    I have used this service since it was first offered and I have been very pleased with Icom's responses and support.

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    Nullius in verba

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