[ICOM] ICOM 746 PRO CW Problem

[J.F. Samuels]

Alan, if the reset doesn't do the trick, put a voltmeter on the Transmit
line in the rig and see if the voltage is in the "gray" zone or fluctuating.
Just could be a bad transmit line driver transistor.

 

John, K2CIB

 

  _____  

 

You wrote:

 

Message: 1

Date: Sat, 26 Jan 2008 12:11:43 -0800

From: "Alan Zack" <k7acz at cox.net>

Subject: [ICOM] ICOM 746 PRO CW Problem

To: "ICOM List" <icom at mailman.qth.net>

Message-ID: <002e01c86057$abda97b0$6501a8c0 at ALANZACK>

Content-Type: text/plain; format=flowed; charset="iso-8859-1";

      reply-type=original

 

I am experiencing a strange problem with my IC-746PRO on CW.

This has been a very dependable rig for the last 5 or so years, allowing me
to get big scores in major contests.

 

My problem is an intermediate CW keying problem.  For no apparent reason the
rig will key itself putting out a steady carrier.  Let's say I am operating
on SSB then switch to CW.  The rig will key itself and I will hear the CW
sidetone in the speakers.  It will do this regardless if the TRANSMIT or the
VOX/BK-IN switches are on or not.  Problem is it will do this at
undeterminable times with no apparent cause or reason.  I can operate for
days, switching back and forth between CW and SSB without a problem.  Then
by just pushing the CW button the rig will again key itself and stayed keyed
until I go to RTTY or back to SSB.  Turning the power on and off does not
effect it.  The last time it did this I disconnected EVERYTHING (mic, key,
ext spkr, etc) so that the only thing connected to the rig was the power
cord and the ant coax.  I turned my power down all the way and switched to
the dummy load and went thru all the items on the menu to see if any setting
would change anything.  They did not.  As it sat there in the CW mode with
the red TX LED lit and the CW sidetone coming from the speaker it just
stopped on its own and went back into receive mode and for the last several
hours has been working fine.  But I know from the last several weeks
experience it will key itself again for no apparent reason at an unexpected
time.  I am reluctant to send it out for repairs as it could conceivable sit
on a bench for a week or more without doing it as there seems to be no rhyme
or reason as to when the problem will appear.  As I said, it only does it on
CW.  As soon as I select another mode it unkeys and everything is normal.
The most local explanation would be something on the desk is touching the
key paddle causing a key down situation.  But it will do it with NO keys,
paddles, etc, connected.

Has anyone ever run into this before or have any suggestions?  They would be
appreciated.

TIA & 73, Alan, K7ACZ

_______________________________________________________

Alan Zack

Amateur Radio Station K7ACZ

Official USCG Auxiliary Comm Station

Las Vegas, Nevada, USA

Delta Rocket Quality Engineer, The Boeing Company, Retired Aviation Chief
Warrant Officer,  U.S. Coast Guard, Retired