[ICOM] Mic problem on IC-756-ProIII

[Ken Winterling]

Jim,

There may be a loss of the DC voltage that coexists with mic audio on Pin 1
of the mic jack.  Check that Pin 1 of the mic jack has approximately +8VDC.
as measured to Pin 7.  The Icom electret mics require that voltage for
operation.  The Heil mics, I believe, are dynamic and do not use the
voltage. They have a DC blocking cap.

Ken
WA2LBI





On Wed, Jun 26, 2019 at 11:35 AM JimR <KD1YV at oneyv.org> wrote:

> After being in non-climate-controlled winter storage and a 500 mile
> move, I put my 756-III in service.  I tried the stock mic, an HM-36, but
> have no RF power, and no indication on the ALC meter. I swap in my Heil
> pro headset, and the mic in that works fine.
>
> So I figure my HM-36 did not survive the cold.  I call HRO to order a
> replacement, but they tell me it is discontinued, and offer me an HM-219
> which I buy.  I plug that in, but it has the exact same symptoms.  No
> RF, no ALC.  Again the Heil headset mic works fine.
>
> As an aside, I plug in my SM-30 mic, and it has the same symptoms, but
> it has been a bit flaky for a long time, so I can't say that is a valid
> test.
>
> Has anybody already solved this problem?  Thanks!
>
> --
> 73 de Jim, KD1YV
>
> -