The Green Screen generation of 5000 controls only allowed for hardware handshaking and had a special pin-out. The Standard 25-25pin connectors will not work. (Assuming 25pin to 25pin) 2-3, 3-2, 7-7, 1(machine side)-cable shield remain the same, but do not jumper 4 and 5. Instead, run the machine's pin 5 to the pc/btr's pin 4, and the machine's pin 9 to the pc/btr's pin 5. If you look in your schematics, the RS-232 pinout refers to pin 9 as "register". This pin actually toggles for every bit received, instead of being used as a buffer full command. This has been the issue in 90%+ of green screen RS-232 setups I have seen. I believe I have a write-up on this setup including parameter locations somewhere in my old notes if you require more information.