Oh you poor soul, feel for you. Spent many long hours on that crap. Sync switch at top should start plugging so check tach and tach belts for slippage. Also make sure your not slipping traction. Try your best to sell a mod. Very obsolete stuff using a form of DC plugging for reduced speeds. Make sure blower motor works or that motor will fry eggs. Check all connections on the SCR's gates. Possible SCR failing. Be careful on swapping stuff around. The boards on the SCR's look the same but there is different resistor values for different positions.

Thanks. Going back today for another ass whopping! I'll post what I find.

We got it. (I think). Contact failure on 203. The main potential contractor. I was monitoring the plugging voltage and the AC feeding the plugging SCR and when the car went in the overhead I saw no DC plugging voltage. But more inportantly, no AC voltage feeding the SCR. Feed comes directly off 203.
Hope this helps someone who has to work on this equipment in the future!

Ralph,
Thank you for posting what you found...