The LK201 keyboard is used across the 2xx, 3xx and on some of the 4xx
terminals, so yes, as I remember, the vt220 keyboard will work with the
vt320.
Can't help with the diagnostic. I am sitting in front of a VT330 now, and
I just looked at the manual for it. it says if the power indicator flashes,
check the ROM cartridge on the rear has to be inserted correctly. I didn't
think the VT320 had a rom cartridge, so that troubleshooting probably
won't help.
Joe Heck