Ok, we made some progress... and a minor set back.
The cab is a hack job of wiring, the Auto/Manual, Advance and HS Reset switches where replaced by regular switches and the harness hacked...
Switcher was hacked in (harness chopped).
Second ISO in the cab, which appears to come off the main ISO into the second one and then feeds the PS board??

As soon as my camera batteries are recharged I'll take some pictures.
What we did
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Jawn brought the game over, and we fired it up. Bad rug pattern as shown in the pictures. All 4 LED's on solid.
Started checking connectors, and found that when I moved the Ribbon cable between the CPU and ROM board the game would show the correct rug pattern and would boot.
Pulled that off and crimped down on the connectors, re-installed.
Game now has Rug pattern that appears normal, get 4 LED's that blink then go out (Yeah!). Now the game is in the settings/bookkeeping and won't exit. Every time we go to Option 28, then forward, it resets and goes back to the Settings screen.
So I find a donor board, pull the 5101 off it, and the 4071 and replace those, same results. Don't know if those are any good, might not be. We also replaced the batteries.
Same results.
While doing this, the Sound board decided it was tired of working and gave up... So we'll add that to the list of things to fix.
Power Supply board needs a LOT of work, so we'll probably stick with the Switcher for now.