[amsat-bb] Re: IC-910H low audio problem.

Ronald G. Parsons w5rkn at amsat.org
Tue Jun 9 05:44:22 PDT 2009

I discovered this with my 910H. If you compare the schematic with an older 
Icom transceiver, say the IC-756, you will notice that the voltage divider 
on pin 8 decreases the audio on that pin by a factor of about 50 from the 

I thought of two "cures":

1. Modify the radio by replacing the offending resistor.
2. Modify my headset by bringing the line that would go to pin 8 outside the 
mic connector and run it to a 1/4" phone plug.

I chose 2. I plug the phone plug into the nearby headphone jack when I use 
the headset, or pull it out to use the speaker. Works on both my 910 and 

I was told by a person at Heil that Icom made that change to better use a 
TNC with the mic connector on the 910.


> Date: Tue, 9 Jun 2009 05:21:35 +0300
> From: Kostas Ioannidis <kostas.ioannidis at gmail.com>
> Subject: [amsat-bb]  IC-910H low audio problem.
> To: AMSAT-BB at amsat.org
> Message-ID:
> <6cd5903a0906081921k5cb111e0j945fc7b09e7d040 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> According to the IC-910H manual, pin number 8 at the mic connector is
> audio output (which varies according to af control). I connected a
> pair of headphones at the pin but the audio is way to low and cannot
> be used for listening.  Is it normal? I thought that it was designed
> for this purpose. Am I missing something in the menus? Thanks in
> advance!
> 73 de SW1IXP, Kostas Ioannidis

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