I am troubleshooting a Time Crisis II now...game works, pedal works, guns have sound, recoil works, trigger pulls register ammo being used but there is not tracking on the screen.
I have checked the monitor brightness, no luck.
I saw on there a way to check the sensor and this is what I just found on another site to check the opto with a flashlight:
Checking the optical diode: three wires connect to this part: a black, red and yellow. First check there's +5vdc between black and red. You should also get +5vdc measured on the black and yellow wire. Now shine a flashlight into the opto led, and this +5v on the yellow wire should drop to (almost) 0. There may also be a capacitor on there too which often fails, so check and replace this too if necessary.
I am going to test that next and see if I just have a bad Opto sensor...