I've read from a few experts that it's a good idea to not turn that old pin on the moment you unload it from your vehicle. Take a chill pill and run a few checks first to avoid burning up components or even your property... If you are an experienced pin tech, please review the list and let us know what else we should consider before turning her on... thanks!
(This is a minimal list in no particular order, there is more you can check first if you desire)
BEFORE you turn it on review the following:
1. Batteries: replace batteries and ensure battery holder has no cracks or broken contact points. Examine below the batteries and ensure there's no damage. (Eventually, get the batteries off the board completely)
2. Boards: ensure all the boards in the backbox are mounted and grounded with screws. Several reasons for this. (Frequently there are some missing, which can allow for more board flex when plugging connectors back in. More screws = better grounding.)
3. Coils: Check the resistance of each coil against the spec. Check each arm and make sure there's no resistance to movement. Check each lug and look for broken/loose wires.
4. Docs: Get your game's documentation at www.ipdb.org
5. Flipper Coils: check them against the specification for right type. Inspect flipper switches.
6. Fuses: Check fuses against the specification
7. ICs: Make sure no socketed ICs (integrated circuits -- "chips") are installed upside down
8. Loose Items: After setting up the pin, before you plug it in, check the cabinet and back box for fallen loose items, using a bright light -- make sure no small parts have been wedged in somewhere
9. Power Cord: Check the power cord for damage and fraying. Be sure there is an undamaged grounded three prong plug installed.
10. Serial Number: Record the serial number, take pictures for your records
11. Voltages: Check the voltages on the rectifier board (with connectors unplugged) -- see various troubleshooting guides to learn what voltages to expect
12. Wires: Check under the playfield and make sure no wires are getting eaten away by moving parts (sling shot wires, and wires along the edge of the playfield that can rub against the cabinet sides) Check the coin door for clipped/cut GI wires that may be dangling free.
13. Nut check: A loose or missing nut can mean undue stress going to a part that is loose on the playfield. Make sure all posts and pop assemblies are well secured. Review all nuts quickly. You will likely find a loose or missing one on your first pass.
14. Add Fuses: Perform this safety mod on all your Williams pins made from 1977-1987. -- add two fuses to the bridge rectifiers to prevent fire. http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11 (see section 4.2 Power Problems) Also see vid1900's tutorial on how to set it up: http://pinside.com/pinball/forum/topic/vids-guide-to-bulletproofing-williams-system-6/page/2
Can you drop a few hints of things you like to do after purchasing a used pinball machine regarding reviewing anything related to power?
I know to check fuses right away against the specification. Looking for more safety/power tips like this. Not looking for cosmetic/playability tips.
I'll udpate a Summary (above) as comments are added.
As you write up your suggestion, please include a link to any item to purchase, add any pic that can help show what you mean (if you have the time), and please include a few steps for those new to electrical issues or pinball. (For example, try to put yourself in the shoes of someone who doesn't know how to use a DMM, and include a few steps to help that person out.)
PS: When you are done, you may want to move onto the next checklist l-)