CAT control via PC of new OM Amplifier

ScottAC8DE

I've recently purchased a new OM 4001A amplifier. The transceiver is a 6500. I can't get CAT control to work from the PC port and the computer interface. I can get it to work via the amp's TCVR port and direct connection to the radio. I'm using the same cables for connection to both methods. FTDI serial/USB and null modem cable.

I've done all the basics. Note I've been using a Flex since the very early days, so I "grew up" with Flex having to start with external cables, then external software for CAT ports and finally to today's "baked in" CAT program, so I have a firm grip on how it all works. I won't claim to the the end all expert, but I know how it works and how to set things up.

-I have 4 different FTDI chipset USB/serial adapters. All check out and work. The PC recognizes them fine.
-I have chosen a high number for the com port just to insure no conflicts. I have tried low numbers as well.
-I have 2 different null modem cables; one purchased and one I made. I have physically checked the pin-out with a meter of both for continuity and shorts.
-I'm using the "existing" setting in CAT and confirmed the port number matches device manager.
-I have confirmed the baud rate of the port in Device Manager matches the amplifier setting. Port set to 9600 8-N-1 no handshaking. I have tried other baud rates changing at both ends. I have tried both Xon/Xoff and hardware handshaking for laughs which made no difference, but now back to none.
-I have tried direct connection to the PC's USB port as well as introducing both passive and active USB hubs. Added the active hub to see if it was a voltage drop problem with the USB as the cable is a total length of about 20 feet, as the amp is in the adjoining room. (rushing air fan noise isolation)
-The USB port I am using on the computer works fine with other devices.
-Latest SmartSDR+ v4 (v4.1.5.39794)

So it seems to be coming down to it's either software problem with SmartSDR CAT or the actual PC port on the amplifier is bad (or it's programming).

Scott AC8DE