I get a lot of email asking how to fix that or that. Unfortunately, without being there, it's hard to say. I'll share some tips here that I know of - perhaps you use others which are just as sound.
Without reinventing the wheel start with this website ( http://marvin3m.com/fix.htm ) - they've already written a lot a great stuff. I'll add here some specific repairs as I come across them.
Stepper Repair - step by step walk through of a William's Circus Player Up stepper.
Cheap Back Box Light Bulb Removal Tool
I haven't shown this on the other pages but here's a nifty way to remove those bulbs from the inserts on the backbox. It's just a rubber hose / fuel line with a slice about 1/4 inch down. When you place this over the #44 bulbs it stretches around the bulb and grips it. Just turn and removed. Should cost about $1 from any auto parts store or free if you got 3-4 inches laying around. You can also use a shooter rubber or, well, a lot of things but I like the hose because it's easier to hold.
Williams EM Score Reel Won't Advance / Game Won't Reset
Here's a difficult problem. It manifests itself as either an intermittent or permanent problem but is not so obvious to see. Here's the score reel mechs from a William's Jive Time. The 9's and Zero switch locations are giving problems. The symptoms are: The game won't reset sometimes and, when it does, the 10 Thousands won't advance when the Thousands goes from 9 to 0. You've checked the zero/nine switches and they're fine but still the problem persists. You go hunting for a switch on the score motor or other location but everything checks out.
Look closely at this picture. Everything looks normal. Note the wire joining the bottom and middle leave blades on the left. This will appear normal and, in many cases, the machine will seem to work normal except sometimes it keeps running and won't reset - you know - chung, chung, chung, chung, chung ..... chung, chung, chung, chung, chung ..... and on and on...
If you push up a little to separate the tabs you'll find the connection has broken and had been just lying together. Perhaps the tabs had enough spring to keep the connection intact long enough that you'd never saw the problem while shopping it. Problems like this plaque older machines. Solder connections deteriorate over time where stress is involved. You've seen the pin connectors on William's system 4,5,6 boards requiring re-soldering - this is an EM pinball equivalent.