Picked up a used RFX9600 to use with my TSU9400 for RS-232 control of a new LG OLED TV. After reading a long list of search hits on this forum, I seem to have solved the problems getting the TSU9400 to connect thru an ASUS AP, using static IPs, i.e. the icon next to the battery status on the Home page shows a WiFi symbol. This supposes that the TSU9400 actually is talking to the RFX.

I made up a quick test screen to put a couple of buttons that send ascii strings to a RS-232 port (using ProntoEdit 1.1). My problem is that the RFX never shows any RS-232 LED activity, nor any busy LED. Since the communication seems to be functional, I'm assuming the problem is in the RFX. I've tried 2 different ports in the 9400 config, no joy. A scope shows a steady -6v on the TX-out pin of the port.

I'm lost as to how to troubleshoot this. I don't fancy tearing the RFX unit open as that would probably be a waste of time. Any suggestions on what to try next?