I have this exact keyboard here.
Some years ago, while I was trying to trouble shoot problems with an A2S1 not typing, I tried using it there and something must have blown up, because after that it wouldn't work with anything.
I've done some troubleshooting with a logic probe and am not finding a clock signal on the 74273 pin 11, which I'm thinking should be there. I had originally thought I'd blown the EPROM, but when I probe the output legs there is activity when keys are pressed.
I've also accidentally shorted pins on the 273 or the 74123 below and had it burp out stuff at the prompt.
A schematic for this thing would be ideal, but I've not yet found any. Since we know the motherboard is basically a clone of the Apple II board, I thought maybe one of you would know -- pin 11 on that 273 seems to connect to pin 2 on the keyboard header, which according to the II schematic is STROBE -- would it typically be the keyboard generating the clock/strobe there? Or would that come up from the logic board?