it isn't uncommon to pull up a post that says "i don't know how to read the schematic"... since reading and understanding the schematic is an important skill when it comes to pinball repair, and it is one i did not have, i figured i'd share how i learned, any maybe it will help other "new people" through the learning curve... it really isn't hard once you don't let it intimidate you...
1) the schematic is a "logical", not "physical" layout of the machine... switches that look like they are right next to each other in the schematic are often nowhere near each other physically...
2) the score motor is "stupid", and the relays/"action switches" (such as a rollover switch) are "smart"... the score motor does nothing except for turn, it does not selectively actuate its switches, it actuates EVERY one of them EVERY time it rotates... it does not "know" what it is doing, the only thing it "knows" is that it was activated by "something" occuring, but it does not know what that "something" is... ALL of the "logic" of the machine is controlled by the relays and action switches... this is a key point to wrap your head around... an "action" fires a "relay" which (in addition to other things, like firing other relays, etc.) fires the score motor... edit: see example in later post...
3) take 5 minutes and learn the symbols... most of them are very straightfoward (such as normal switch states, coils, etc.)... there are only maybe half a dozen that are regularly used, so this doesn't take long...
4) understand the concept of "machine state"... for example, a gottlieb schematic is drawn with the game started, a ball served in the shooter lane, and then turned off...
5) "normal" state for switches isn't always the state that the switch is in most of the time... this can be deceiving when you are looking at stuff like "hold" relays, as those may almost never be in their "normal" state during game operation...
6) sit down with your schematic, and start tracing "what happens if?" scenarios... for example, you know that if you hit a pop bumper, it fires the pop and scores x amount of points... find the pop bumper relay on the schematic, note which switches are on it, and find all those switches... then trace the path that mr. electron follows when each switch is actuated... once you do that, move on to another function until you have worked your way through every action the machine can perform.... this may be a bit frustrating at first, but after you have traced 4 or 5 circuits, it will quickly become easier... having a few of your favorite beverages during this process makes it more enjoyable... 
this is the time consuming part, but imo, the only real way to learn a skill like this is with a big hammer... you just have to do it over and over again until it becomes second nature... someone (like me, in this case) can tell you "how to learn", but sadly, a vulcan mind meld isn't possible, you gotta do the actual learning part yourself...
7) in addition to all of the above, tutorials are given on a daily basis in the tech threads... even if the thread isn't about your machine, click on it anyway... if a picture of a schematic is posted, there is almost always a response (sometimes several) where someone traces the desired logic path...
hopefully this will help out some people... if you put a few hours and some effort into it, what is seemingly a jumbled mess becomes something you can easily read and understand... it will also allow others to help you better with problems that come up if you can present the problem to the community with more than "it doesn't work"...
comments welcome...
Lady Lake, FL
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Edmonton, AB
