Pocket Computer (MC-2200)
Microcassette Recorder & Printer (MP-220)
I had two items broken on my board: printer paper advance pushbutton and NR-HL-3V relay. I replaced the button with some microswitch of roughly the same height and removed the relay. The relay seems to be used to control tape recorder motor power and operating in NC (normally closed) mode. When it is removed, it will be possible to operate the tape recorder any time, without the commands from the pocket computer.
It is easy to find replacement batteries today, look for AA size NiCD 1.2V cells.