Quoted from Pahuffman:
It started to smell immediately on turning the game on. Newish Rottendog power supply - should have gone with X-Pin, but I didn't know they existed when I bought the new one.
RD isn't necessarily the issue, original DE supplies have many miles on the and the caps are known to be a common issue.
Open the backbox and cabinet and turn the power on for 5 to 10 seconds and see if you can identify anything. Do a close visual examine of coils before powering up to see if one has a burned wrapper. DE also known for smoking the laser kick coil for some reason.