Down to the nitty gritty,
Alright, There a number of thing that could have gone wrong, but we'll need some specifics other than "won't turn on"!
Does it hum, the light turn on, or anything?
Let's list some possibilities, shall we?
Humming indicates you've frozen the motor (The motor cannot freely spin). You could have done this by not fully tightening a screw, causing the fan to hang on it (Or some other rotating motor part).
If the light is coming on, You've likely messed something up with the speed switch. I'd take it apart and look for lose wires, broken contacts, Etc.
I'm guessing you're referring to the Original Heritage I of 1981-1984, But in the event it is a Heritage II (Grey bag with black), You'll notice a Red light on the top of the power plant (Motor). If this light is illuminated, You have power to the cleaner. I suppose you could take an Ohm meter to where the cord plugs into the cleaner to test for broken electrical contacts.
Have fun!