Originally Posted by Keefusb

My wife had a similar set-up on her mid-90's Cannondale H300 hybrid. You said that the shifter part number indicates a shifter that is made for a triple chainring, so you are good there. The FD definitely looks like an FD made for a triple. This crankset has steel chainrings IIRC, which are heavy but very durable. One thing I have observed about this type of set-up is that you will never be able to shift onto the big chainring when the rear derailleur is shifted onto the larger or largest gear in the back. You have to always be in one of the smaller rear gears. Also, if you are using Grip Shift shifters or similar which was very common back then, you sometimes almost have to "over-shift" to get onto the big ring. It's also possible that your chain may be a link or two too short which would make the shift onto the big ring difficult.

When you are setting the cable tension for the FD, it can help to have something wedged between the seat tube and the outside of the inner FD cage to ensure the FD swings and stays out far enough to put the chain onto the big chainring. Someone mentioned an orange plastic piece, but you could use a plastic screwdriver handle or similar in the same way.

I think it's probably a combination of adjustments and not trying "forbidden" gear combinations when trying to shift onto the big ring.