Looking at the parts breakout for the Super 990, my 33-791, and the current production model 33-891 you can see some evolution in the motor. The Super 990 motor and my 33-791 motor look quite similar. There are some slight differences in the motor when going from the 33-791 to the 33-891. But the mounting, how it attaches to the yoke is similar with minor changes.
So I’m wondering if you could adapt a 33-891 motor, which I’m sure would be available, to the Super 990. If the distance between the yoke arms is the same or wider that may be doable. Some machining may be necessary. The rear pivot pin looks to be a larger diameter so you’d probably have to purchase the pin and the hole in the yoke would need to be reamed. I say reamed because you want a good fit and you wouldn’t get that by just drilling the hole larger. And reamers are cheap. The front pivot point hub, or Front Trunnion as Delta calls it, may have to be replaced with the one the 33-891 uses and some machining may be necessary for it to fit in the hole in the yoke. Or possibly the old Front Trunnion could be used by drilling it to mount to the newer motor. Worst case one would have to be machined from scratch. Something any machine shop could easily do. It wouldn’t surprise me at all if the Front Trunnion from the 33-891 would fit perfectly in the 990’s yoke, Delta changes things slowly once they have a good design.
I’d possibly consider taking this route, unless Delta wants my first born for a 33-891 motor. But it might be possible to pick one up surplus on the cheap. Or a 33-791 motor or any in the 33-89x or 33-79x family. Course I have an edge, a metal lathe and milling machine so I could fabricate the parts I needed.
-- -Curt, Milwaukee, WI
