Last year I picked up a mint Beseler 45MXT enlarger, 45S dichroic lightsource, 3-lens turret loaded with Nikkor lenses or 50 mm, 105 mm, and 135 mm. Unfortunately the lightsource, although it looks brand new, is dead. I am just now setting up the enlarger and can't figure out how to remove the lenses (and then install different lenses) in the turret. Each lens has two retaining screws which I can remove, but then I can't access the retaining ring. Any advice is appreciated. Thanks.