(ET) Working on card 1-E15, logic and why CR111?

[Christopher Zach <cz alembic crystel com>]

Working on my favorite thing, rebuilding this CR111. So far I have 
replaced all the diodes, and replaced Q104 with a simpler 2N3391 
transistor instead of the old whatever it was.

However something interesting: My board doesn't have a CR111 on it. 
Instead the collector of Q104 goes to a hole where it is supposed to 
attach to another diode that then goes into the collector pin on the 
board. Odd, it looks like they added CR111 as a hack on the first 
generation boards, I wonder why.

In the meantime though I am beginning testing and getting a bit 
confused: I would assume that the first thing one would want to test is 
that the darn thing will energize 1A if you have the key, seat, brake, 
and start switches interlocked but only if the key is off or something.

On this board if I ground pin 12, then put voltage on pin 5 and 6 
together the output of pin 4 comes on (it's sinking a 30 ohm 250 watt 
resistor as a sample load) and stays on even if 6 is removed. However if 
I remove 5 it drops out and will not come on again until I bring pin 6 
live with power on pin 5.

I think this is wrong, but can someone cross-check? I think the 
connection between pin 6 and 5 should be an either-or, charging up C102 
to the point where it can hold the gate of the SCR 102 live until the 
switch clears over to pin 5.

Wait a sec... I'm testing with 12 volts. Bringing the bench voltage to 
24 seems to allow a very quick switch between 6 and 5 to bring 4 live 
(sinking 600ma, I need a bigger resistor). I think that's it; if I came 
up to 36 volts it would probably hold the latch long enough to do a nice 
slow switch.

So it looks like the 1A circuit may be working, does anyone else have a 
"truth table" to test the rest of the board? If not maybe I should build 
one.

Chris