[Elecraft] K3 unexpected TX after iMic + CocoaModem

[Tighe Kuykendall]

Strange issue and haven't found much by searching.

I use a MacBook Pro with my K3 and KX3.  It had worked fine for rig 
control and with the K3/P3/KPA utilities.  I added an iMic audio 
interface (bought it for the iPad and was experimenting) and setup 
CocoaModem for use with the KX3 to do digital modes.  When I connected 
the MBP back to the K3, any type of USB activity for rig control or the 
K3/P3/KPA utilities causes the K3 to go into TX which can't be stopped 
except by unplugging the USB from the MBP.  If there's no USB control 
activity with an app, the K3 works normally.

I simplified the radio down to just the K3 with no other accessories and 
it still happens.  KPA utility works as expected with the KPA, even with 
the K3 powered ok and it going into TX.  I checked for grounding issues 
and reseated all of the serial cables.  The USB ports work normally for 
everything except interfacing to the K3.  I tried a different MacBook 
with the K3 and it works fine, so it's something with the MBP side of 
the USB connection on my shack laptop.

I then took a questionable troubleshooting action to test K3 
communications, which I had planned to do anyway, was to move to the new 
beta K3 firmware.  I forced the K3 into MCU Loader and upgraded the 
firmware with the shack MBP.  No issues in communicating with the K3 
during the upgrade.  Once the K3 was back operational, same issue as 
before with unexpected TX on rig control.

Anyone experience an issue like this before?  Thought I'd ask before 
stripping CocoaModem and related pieces off the shack MBP.

Tighe
NK4I