vr sensor
 

ms1 board 3
I rigged up my 85 dizy with msd and that works fine i used the trailing coil for a tach signal but it was wildly inaccurate
I tried using vr pickup with the 4 pin gm ignition module to get a signal but that seems to not work well.
is there any other way to rig up a vr pickup for these first gen dizzys

You can use the coil (-) as an input if you add resistance to the tachin line. Try 50K to start. It will work, been there, done that for many thousands of miles on a 12A runing MS. If 50K ohms doesn't work, write back and I'll expand on this issue.

-Mike

Edit: Also, doesn't the MSD have a tachout line w/ 5v square wave?