Thanks KennyV - did not know that.:thumbsup:
OK - I have started from scratch with nothing connected, checked voltages, and connected one item at a time. At each point, I checked voltage, and manually turned over the starter by shorting the solenoid. I have installed fuses one at a time and validated that the voltage is steady. I have everything connected, all fuses, and I can start the tractor with the manual starter method. I am at the point where I have been before - everything seems OK, but if I turned the key to crank, it crashed. Before I try to crank with the key, I want to verify the starter-key system. I had to stop for tonight, but will continue tomorrow.
Since the main thing (only thing?) that happens when I turn the key to position 2 for cranking - is to provide power to the starter relay, I am investigating the relay. One thing I noticed with the relay removed from the plug is that there is 12v across the "coil" wires on the plug when the key is "on" (position 1). I did not expect to see 12v at the coil until the key is switched to crank (position 2).
Should there be 12v on the starter relay when the key switch is in position 1 (on, but not cranking) ?
There is also a diode assembly - I think it is called a flyback diode. I have no experience with this, but a little googling makes me think that even if the diode is shorted or open, it should not cause 12v on the coil.
I will be checking the key switch tomorrow - but I am pretty sure I originally checked for 12v on the position 2 tab, and it was OK.