The H-9 was flakey even when it was introduced. It was not a reliable
product, and will probably be difficult to get working. Probably bad ICs
or, worse, bad IC sockets.
Do you have a complete H-8 (or several)? By complete, I mean chassis & CPU,
reasonable memory, disk controller, serial I/O card and the "CP/M Card" (a
tiny small card, only about 3 inches wide, that allows the computer to run
CP/M ... I think that the original name was "extended configuration card" or
something like that).
In my opinion, the best terminal for old PCs is an old laptop using a
terminal program through it's serial port.