This is the special level-shifting RS-232 cable needed for the Tandy Portable Disk Drive aka Brother FB-100.

For wiring and build directions see the github project page.

Print the housing in SLS or MJF nylon.

If you make multiple cables, you only need one soldering jig. The soldering jig is just to hold the 2x4 connector in the correct position so the pcb is centered and parallel while soldering.

The cable in the BOM has 2 different plug ends, so you can make 2 cables, one for connecting the drive to a TRS-80 Model 100 or any other Kyotronic KC-85 clone, and one for connecting the drive to a TANDY WP-2 or any normal PC com port or usb-serial adapter. To make both cables, double all the components except the cable.

There are cheaper versions of the 2x4 connector instead of the $2 one above, but this connector is selected to reduce wear on the pins in the drive. The cheaper sockets are simple fork type contacts inside which make a good connection but grind into the pins fairly aggressively, not meant for repeated insertions. The particular part in the BOM above has a folded sheet construction with open back that doesn't wear the pins down each time it's inserted.