Futaba FP-T4L interface hints - Successful interfacing of an old Futaba

[chall]

I got an early 90's Futaba AM transmitter in with some other old R/C stuff. It has no buddy box plug, so I had to go in and find the right place to attach my wires to the PC. This was not as hard as I expected.

A white 5 conductor connector separates two circuit boards within the unit. One has lots of RF stuff, the other is connected to the joysticks. I figured the signal I wanted had to be on that connector. Inspection shows this:

Pin 1 - unknown (white wire in photo)
Pin 2 - unknown
Pin 3 - ground (green wire in photo)
Pin 4 - ground
Pin 5 - antenna

Tests showed Pin 1 was the signal I needed.

Pictures are here:

To get the signal to work with FMS I needed to connect through the little one-transistor circuit described here:



I used a transistor from a bag of Radio Shack transistors:
RS 276-1617 "NPN Switching Transistors (15)".

Good luck to anyone else trying this. These older units aren't as complex as the newer ones... and that's good!