(ET) Diagnosing delay error on E15 board

[CZ <cz alembic crystel com>]

Ok, so this weekend I literally blew a relay up by moving the lever from 
forward to reverse without even engaging speeds 1-3 reverse. Tractor was 
moving forward, took speed to 0, then my hand slipped and the throttle 
went left.

Boom.

This should not happen. There needs to be a delay in closing the relay 
until the armature is at *zero*.

Looking at the schematics, the key seems to be pins 7,8,9 on card 1. 8 
applies +36 to the circuit when the reverse switch is closed. 9 is where 
the relay is. Between them is an SCR that has to be triggered in order 
for the switch to engage R. What seems to control this is 7, which is a 
+36 volt line coming from that goes on wire run 8 which seems to connect 
to the positive side of the motor after L1 and L2.

From there it goes to Q105, then into a diode/resistor network which 
controls the gate.

I wonder if this is a NOT circuit such that only if there is no power on 
7 will it allow the SCR to energize. Otherwise it holds it off. But that 
doesn't make sense, as you can't go from F to R while in speeds 1-5, 
it's mechanically not possible based on the throttle assembly.

But if you open L1 and L2, maybe there is a residual voltage there till 
the motor spins down? Maybe. But what does C106 do?

Hm.

C

through Q105