Not much of a chance of blowing something up which is one of the many great things about EM machines. When I get a pin and some of them haven't been turned on in decades, I open the hood and backbox and do a search for any obvious issues. Most times though, it'll all look ok. I then replace all fuses with the correct spec ones. The only way to proceed from that point is to turn it on and try and start a game and see what the problems are, if any and this is where a schematic becomes invaluable.. Also, you can post what it's doing on the pinball forums and they'll be of tremendous help. Scan and post your schematic in of the relevant circuits to help the guys on the forums help you.