[ICOM] Re: Icom 746 PRO CW Problem

[William J. Wickstrom]

Alan:

I'm not sure if this will help or not, but I was experiencing a similar
problem with my '706mkII. It sometimes exhibited the "transmit CW for no
apparent reason" symptom if I changed bands with the UP/DOWN band button, or
memories that involved a band change with the M-Ch knob. The radio had the
"Tune Module" made by Better RF connected to the 4-pin Molex connector on
the back that is intended for the AH-4 auto tuner. The Tune Module is a
simple circuit designed to enable the TUNE button on the front panel of the
rig to transmit CW at about 10 watts for a period of about 30 seconds,
allowing the operator to tune his antenna at the operating frequency. If I
removed the Tune Module, everything worked flawlessly. Do you have anything
connected to this 4-pin white Molex connector on the radio? Seeing as you
have indicated that you tested using low power into a dummy load, RF
feedback sounds less likely.

Another thought: Try (if you haven't already) disabling the AutoTune
function(s) in the menu.

If you figure it out, please let the group here know how you did it.

Jim, W1IK

-----Original Message-----

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 it's 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