Slot Machines - The Basics
Slot machines are by far the easiest - and one of the most fun - games in the casino to play. Simply insert your coin and pull the handle. One of the oldest jokes in the world is to call slot machines "one armed bandits" because - with some of the highest odds against you in the casino, that is exactly what they were - and still are! However, it's now more appropriate to simply call them bandits, because you don't have to pull the handle anymore - just push a button. Electrical motors and computer chips do everything else.
HOW SLOT MACHINES WORK
Decades ago, when slot machines were young, they were basically mechanical devices. The force of the handle being pulled down turned the metal gears that turned the wheels on the machine.
Later on, electrical motors were added to turn the wheels and the force of the handle being pulled no longer had any bearing on the results. In fact, you no longer had to pull the handle, since the wheels were electrical. All you had to do was push the "play" button to start the wheels. The odds were controlled by how many winning symbols were on each wheel.
More recently, most casinos have are converting to computerized slot machines that no longer have wheels at all - just a computer screen that plays a video simulating spinning wheels. A computer "random number generator" determines the results. As soon as you put your coins in, the result is predetermined.
Whether you pull the handle slow or fast, whether you use the handle or the play button, whether a jackpot has recently been paid on that machine or not, none of these has any bearing on the result. It's randomly determined each time by the computer. The casino can set the payout high or low simply by changing the computer program, although they are carefully regulated by the state to ensure the numbers are truly randomly generated and that the overall payout percentage is what the casino says it is.
Since the results are completely random with each play, the fact that a machine hasn't paid a jackpot for a long time doesn't mean that it's "ready" to pay. Conversely, a machine can pay several jackpots in a row. It's simply impossible to tell if a machine is ready to pay a jackpot.
As the saying goes, "You pays your money and you takes your chances."