Msr 2000 RI300 interface.... 

With a working system.

Wire ri300 to back plane board remove all boards except f1-"pl" board and station control board. 

Revision audio and dpl injection
Exciter J102 connect a wire from pin3 j1 ri300 to pin 15 J102 backplane board exciter board for audio and dpl injection this 
give the proper dpl waveform on the scope.
  pin 12 J102 exciter  

Ptt is connected from pin 4 J1 ri300 to e22 backplane local ptt.
from pin 1 J1 ri300 to 12v to e12 backplane. Use a fuse.

Receiver J202 connect pin 2 J1ri300 to pin 5 J202  the discriminator on the backplane board.
see pictures.

1. Goto controller and refer to you manual for jumper settings.
2. Put jumper between 2-3 on Jp4 for dcs and audio output on pin 3 at J1. revised
3. Jp1 is open. Jp5 2-3 to drive modulator directly.

I want to thank K2JRC for helping in this project. If you have anything you want to correct please email me at n2kpk@arrl.org