When you power on does ANYTHING come on? If nothing at all then you either have a mains fuse blown in the power box where the line cord comes in or a breaker on the house circuit is tripped.

On later Williams games the power cord itself can become unplugged in the back (common) but I can't remember if DE games ever used an unpluggable power cord or not. Wouldn't hurt to have a look

If I remember correctly my SW had the power cord wired directly into the on/off switch box in the front right bottom cabinet.
Check the 8A (110v) or 5A (220v) Slow blow fuse located in the on/off switch box. You will have to press in and turn the little black fuse holder to remove it.
If that is fine, then take that box apart and see if the round disk shaped varister or line filter is burnt.
Let us know what you find out please.

Dan is right. The MOV, metal oxide varistor, needs to match the voltage you're running. Also if there have been any surges or spikes like from lightning it will blow as thats why it's in there

rare for the transformer to be bad...

but make sure none of the lugs somehow got pushed together and is causing a short.. that was the problem on one machine I was working on.. took me forever to figure it out.

Disconnect the transformer from the boards. Put in a new fuse. Turn it on so that you can see the fuse and watch for a bright flash of light.. if it pops, you've probably got a short. Work your way back from the transformer connector to the plug in the wall.