(ET) Reverse operational on E20 again

[Chris Zach <czach computer org>]

Well, this weekend I once again came to the conclusion that the Elec 
Trak Owner's manual is worth it's weight in gold. I used the E20 
schematic to find out exactly where the wires for the D402 and D403 
diodes (which power the 1A,2A,3A contactors) went and it turns out that 
someone mis-wired the tractor and had the wire going to D403 going to 
the wrong side of the wrong contactor. Thus instead of having a full 36 
volts for the contractors it had only 24-25 volts; not enough to draw 
them in.

Moved the wire to the right post, and everything works. I even have 
cruise control in reverse, which is terrifying as the only way to drop 
out of cruise in reverse is to hit the brake or the key. In forward you 
can drop out by pressing the pedal down but since speeds 5-8 are 
inoperative, it's a bit of a problem.

Now onto the last issue: I think that the drop-out for field weakening 
is not working properly on my E20. Card 4 again. The little copper shunt 
gets *WAY* too hot, but only when I am tooling around in speeds 5-8. 
Thus I conclude that it's acting as a resistor but not dropping out the 
FW circuit.

Off to the drawing board. I should be able to figure this out next week.

Chris