IBM 6094-020 LPFK (Lighted Program Function Keyboard)

Hi, I've just got my two LPFKs -- one of which is now sitting out on the bench. The stuff on the codeninja page about the LPFK protocol seems to be inaccurate; my LPFK is completely mute. I can set the switch on the back to Loopback, which makes the light for whatever keys I press light up, but in "live" mode nothing happens at all. I've got a scope probe on the TX output of the MAX232 (pin 14), which connects straight to the serial connector, but all I've got is a steady -10V (negative ten volts) level. The crystal is oscillating and the 8051 appears to be running code. If I ground the RXD line (serial break?) and then release it, the LPFK resets and does its startup dance. Still no output after this, though. I suspect it's expecting some form of init sequence. Does anyone have an LPFK, the PC connection kit and the relevant software to hand? A serial trace would be tremendously useful. Has anyone managed to get one of these things working? I did spot a thread in the archive started by Michael Brutman -- <http://www.classiccmp.org/pipermail/cctech/2007-July/082612.html>. Nothing after that until Paxton Hoag's LPFK bulk-order earlier this year though. Thanks, -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/