AFAIK, fruit machines are not at all random, and use a computer with a programmed payout ratio. This is used to weight its random number generator accordingly, which in turn moves the wheels, lights, etc. using controlled servo motors. The only light-affected part might be an IR trap that might (I simply don't know) be used to detect and confirm wheel orientation (like the ones in your computer's mouse). It's plausible that blinding these using another light source might confuse the machine, but I can't see why the machine would default to 'pay out' status in the event of this happening.