I found this info from KG4LUQ.
Perhaps it can help You.
Terrific amp and nothing to add to previous reviews except for those looking to interface it to a Flex 5000a:
1)In "Antenna" setting, set tx delay to 40 ms in order to avoid "hot switching" the amp
2)You may need a null cable modem adapter to connect the Kenwood interface cable to the computer's db9 port (I did)
3)In PSDR's CAT settings: set the CAT COM port to the same port as your computer's serial port-9600-none-8-0-stop, Allow Kenwood AI Command and set the ID to TS2000. NOTE:If you are using DDUTIL with the Amp's COM port set up under "Passive Listening"-it won't work until you have the amp following the Flex with the same port in PSDR's CAT setup settings, then you can change the settings in PSDR and DDUTIL and for the rest of that operating session, the amp will follow the Flex. If I can help you, please feel free to contact me.
I would like to thank the following individuals for their kindness in answering my numerous questions before and after I bought the amp:Jim AB2CD, Steve Gilmore W4SHG the manager at HRO Woodbridge, VA and last but certainly not least-Tom Rum W5RUM Tokyo Hy Power technical support USA.