The "Almost A Jackpot" syndrome.

Your talking about the three reel Slots, and not the video slots which are programmed and run by the Random Number generator.
Heres a borrowed example of how they work....
"Reel type slot machines have a number of spaces on each reel that contain appx. 22 physical stops.
Lets say that there are only 10 stops on each reel. With 10 stops there can be 1,000 different combinations. We get this number by multiplying the number of symbols on each reel. (10 x 10 x 10 = 1,000) The 1,000 combinations that can be attained are known as a cycle and this is the word that sometimes confuses a player into thinking that the machine has cycles of winning and losing.
The odds of a three number combination being picked are one in a thousand. Theoretically if you play 1,000 spins you should see each of these number combinations once. However we all know that this is not the case. If you played a million spins you would see that the numbers would even out to be closer to the actual probability.
This does not answer the question of why the machine always get SO CLOSE to that winning combination though does it? Doc? I wish I knew that answer too. I don't know how that is done by the machine, But I am looking into it.
PMM2008