Completely new to cine projectors, have just purchased a Sankyo 2000h from a house clearance shop - still in its original box with accessories and manual. Thought I would see if it works before trying it with some film - it runs fine and the bulb is working but doesn't project through the lens. The lens cap is removed. Has the machine detected there's no film and stops the light shining through? When I turn the knob off from "lamp - FWD" through to "Standby" it does very briefly flash through the lens.