Well this is interesting.....With the help of my Ed Romney repair book, some small camera repair tools I bought 13 years ago and never used until now, and a couple of shutter images provided by fellow APUGer grahamp, I actually fixed the shutter. The speed control mechanism wasn't working - the tab on it that lines up with and slows down the mainspring was not interfacing with the mainspring. When I took the speed control out, I noticed a screw lying beneath it in the shutter. The screw was supposed to screw into the speed control assembly from below, I surmised. Without it, the control lacked structural integrity and the tab could push up and was ineffective. When I reassembled everything with the screw in place, the shutter fired properly on all speeds - except 1/125, 1/250, and 1/500 all look pretty much the same. There is a lot of oil on the blades, and I think this is why. For my next trick I need to take off the rear element (haven't quite figured that out yet) and clean the blades with solvent.
This is of course a rosy summary - the path to success actually involved a few additional learning experiences along the way, but so far so good.
Any idea re: the best solvent? I have VM&P Naptha and barbecue lighter fluid, but no cigarette lighter fluid. I'm open to suggestions - what to use and where to get it.
I'm now glad I did this, because I have noticed that on another lens (105mm) there is also a problem - the top three speeds all fire at 1/500-ish. But not because of oil on the blades. Now I understand the shutter, this may be an easy fix (unless attributable to missing part).