(Topic ID: 84979)

reading em schematics: how i learned, maybe it will help others


By ccotenj

5 years ago



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    #1 5 years ago

    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...

    #2 5 years ago

    Thank you for this posting ccotenj,

    This should be very helpful for me. I am very good with the mechanical parts of this hobbie, but the schematics are my downfall. I will spend more time with my schematics and try to learn as you have suggested. Some of what you said already has made me understand things I was not sure about,

    Thank you very much,
    PinballTom113

    #3 5 years ago

    Good list, 6 & 8 are valuable. Every time I see a tech problem with a schematic snippet I watch and learn. I'd add:

    9) Do a complete rebuild of all components, including a clean/adjust of every switch. After my first one of these, as witnessed in my Big Brave thread, I got the trial by fire chasing down about 12 errors! Using/learning the schematic was mandatory.

    10). More seriously, my latest fun is to pick one of the "bigger" components and work through it in the schematic to validate my understanding. For example, working through the match function, bonus, and other "selectable" options.

    #4 5 years ago

    @pinballtom... you are welcome... feel free to use this thread to post any questions you run into...

    Quoted from btw75:

    Good list, 6 & 8 are valuable. Every time I see a tech problem with a schematic snippet I watch and learn. I'd add:
    9) Do a complete rebuild of all components, including a clean/adjust of every switch. After my first one of these, as witnessed in my Big Brave thread, I got the trial by fire chasing down about 12 errors! Using/learning the schematic was mandatory.
    10). More seriously, my latest fun is to pick one of the "bigger" components and work through it in the schematic to validate my understanding. For example, working through the match function, bonus, and other "selectable" options.

    the best part about the web is that you can get "hands on experience" without actually putting your hands on anything, and you can cram what used to take many years to learn into a very short period of time... just by reading all the tech threads, i learned about em machines by osmosis (plus i practically memorized clay's guide )...

    re: #9... yea, that'll definitely make you learn, whether you want to or not... iirc, you also had the "bonus fun" of those foolish jumped switches to deal with...

    re: #10... i like that... kinda like the "advanced course"...

    #5 5 years ago

    Thank you. I'm pretty good with the solid state side of pinball, but just now getting the hang of working through the schematics. Way2wrd has been most helpful to me. He got my Atlantis mostly working for me. I finished it up and learned a little more as he walked me through the rest.

    I finally"got it" though while helping George with his Atlantis. Mine worked and while looking through the schematics helping him, it just clicked. I knew how my Game operated and seeing it on paper it suddenly made a lot more sense.

    Thank you for posting this. I'm looking forward to starting on my next EM. I just don't know which one should be next.

    #6 5 years ago
    Quoted from SchertzPinball:

    Thank you. I'm pretty good with the solid state side of pinball, but just now getting the hang of working through the schematics. Way2wrd has been most helpful to me. He got my Atlantis mostly working for me. I finished it up and learned a little more as he walked me through the rest.
    I finally"got it" though while helping George with his Atlantis. Mine worked and while looking through the schematics helping him, it just clicked. I knew how my Game operated and seeing it on paper it suddenly made a lot more sense.
    Thank you for posting this. I'm looking forward to starting on my next EM. I just don't know which one should be next.

    you are welcome... despite what he tries to tell us, that way2wrd guy is a cool dude...

    i had the same "lightbulb moment"... after struggling through #6 for awhile, all of a sudden, BAM, it clicked... when an action happened, i could visualize what was going to have to happen logically for the desired result to occur...

    #7 5 years ago

    an example to illustrate #2...

    an "action" occurs that requires the score motor to run, such as a 500 point rollover...

    closing the normally open (NO) rollover switch (the "action") fires the rollover relay coil...

    the rollover relay coil fires, actuating its switches simultaneously...

    - one of the NO switches on the relay closes, firing the score motor...
    - one of the NO switches on the relay closes, completing its portion of the 500 point relay circuit...
    - one of the NO switches on the relay closes, "locking in" power to the relay...
    - possibly other switches doing other things...

    the score motor starts to rotate... it doesn't know it is about to score 500 points, it could just as easily be advancing the ball count or anything else... it doesn't care...

    the score motor opens a normally closed (NC) switch that removes power to any action that requires the score motor... it also closes a NO switch that gives power to the rollover relay lock-in switch...

    the impulse cam closes the NO switch that completes the circuit to the 500 point relay 5 times per "rotation"... each pulse of the 500 point relay fires the 100 point relay (to do the actual scoring, since score reels can only advance 1 position at a time)... again, the score motor doesn't care, it could just as easily be pulsing the 5000 point relay...

    the score motor completes its rotation, closing the NC switch that gives power back to actions that require it... it also opens a NO switch that it closed for the rollover relay lockin switch, causing the rollover relay coil to drop out...

    so...

    "action"... rollover switch closes, firing the rollover relay...
    "relay"... rollover relay, (as well as other relays in the chain) causing "stuff" to happen...
    "score motor"... turning happily along, oblivious to the world around it...

    #8 5 years ago

    Thank you so much for this thread, I am having been actively seeking an EM for the past month or so, and while doing so jumping in the deep end of the knowledge pool trying to soak in as much as possible.

    I know everyone here says it just kinda "clicks" and while that hasent really happened for me your last post was one of the first times I felt a truly understood how 500 points are scored via relays and motors (maybe your words just jive with my brain better than others). I have read through pinballrepair trying to learn, and watching every video on youtube about repair, so now I am down to finding a machine (not easy in my area) and throwing my hat in the ring with the rest of you EM guys.

    #9 5 years ago

    I think the biggest trap people fall into with schematics is over-thinking it. We all tend to build a model in our heads to explain what we think should be happening (rollover closes switch, switch trips relay, score motor starts . . .) until it becomes overwhelming. That's when we start adjusting switches based on hunches and educated guesses, and usually cause more problems than it fixes.

    The best repairman I ever knew was an old school operator, and he used the schematics a bit differently than most. His main tool was an 8 foot jumper wire with alligator clips at both ends.

    He used the schematic, but he would jumper from whatever wasn't working to the first switch shown on the schematic. If that didn't make it work he would move on to the second switch. Eventually he would arrive at the problem, and he could find and fix things faster than anyone I've ever seen. He didn't give a second's thought to the theory involved, the schematic was just a map that showed where to put the alligator clips.

    I just went through this last week. I wasted hours because I was convinced that I knew what the problem was. When I finally gave up, dug out the jumper wire, and started following one line on the schematic, I found the problem in 20 minutes.

    #10 5 years ago
    Quoted from SchertzPinball:

    I just don't know which one should be next.

    Cow poke should be next. Problem solved

    --Jeff

    #11 5 years ago
    Quoted from cjmiller:

    He used the schematic, but he would jumper from whatever wasn't working to the first switch shown on the schematic. If that didn't make it work he would move on to the second switch. .

    I've used this search method. Very useful.

    #12 5 years ago
    Quoted from btw75:

    I've used this search method. Very useful.

    yup... alligator clips and a piece of wire are your friends...

    #13 5 years ago

    Thanks for this.

    #14 5 years ago
    Quoted from way2wyrd:

    Cow poke should be next. Problem solved

    Cowpoke huh? The sing along and the 57 Pitch and bat are pulling at me too lol

    #15 5 years ago
    Quoted from CapsLock42:

    Thank you so much for this thread, I am having been actively seeking an EM for the past month or so, and while doing so jumping in the deep end of the knowledge pool trying to soak in as much as possible.
    I know everyone here says it just kinda "clicks" and while that hasent really happened for me your last post was one of the first times I felt a truly understood how 500 points are scored via relays and motors (maybe your words just jive with my brain better than others). I have read through pinballrepair trying to learn, and watching every video on youtube about repair, so now I am down to finding a machine (not easy in my area) and throwing my hat in the ring with the rest of you EM guys.

    cool, glad it helped... once you get it into your head that the "score motor" is horribly misnamed (as it doesn't "score", and it does many other things), and that it just rotates and doesn't care what it is doing, things go a lot better... side note: this is why many fall into the trap of thinking the score motor is at fault when it runs continuously... they haven't grasped yet that the score motor doesn't care... it just rotates when it is told to rotate, and if an "action switch" is stuck (the common cause for eternally running score motors), it is being told to rotate over and over...

    the score motor is roughly analogous to the power grid (except that only one function can use it at a time)... it really is a "power provider/remover"... similar to the grid, it provides power to all possible outlets at the same time, but whether power is actually "used" or not depends on if something is actually plugged in... activating a relay that requires the score motor causes it to be "plugged in" (completing a circuit) to the score motor...

    #16 5 years ago

    @schertz... ooo, that's a tough one... since "sing along" is at the top of my list, and a pitch and bat isn't far behind it, those would tempt me... but cowpoke would be cool too...

    you could always work on all 3 at once...

    #17 5 years ago
    Quoted from cjmiller:

    I think the biggest trap people fall into with schematics is over-thinking it. We all tend to build a model in our heads to explain what we think should be happening (rollover closes switch, switch trips relay, score motor starts . . .) until it becomes overwhelming. That's when we start adjusting switches based on hunches and educated guesses, and usually cause more problems than it fixes.
    The best repairman I ever knew was an old school operator, and he used the schematics a bit differently than most. His main tool was an 8 foot jumper wire with alligator clips at both ends.
    He used the schematic, but he would jumper from whatever wasn't working to the first switch shown on the schematic. If that didn't make it work he would move on to the second switch. Eventually he would arrive at the problem, and he could find and fix things faster than anyone I've ever seen. He didn't give a second's thought to the theory involved, the schematic was just a map that showed where to put the alligator clips.
    I just went through this last week. I wasted hours because I was convinced that I knew what the problem was. When I finally gave up, dug out the jumper wire, and started following one line on the schematic, I found the problem in 20 minutes.

    Hmm, that is interesting. Not really sure I understand what you are explaining but I understand the concept. What "line" are you following?

    #18 5 years ago
    Quoted from LongJohns:

    Hmm, that is interesting. Not really sure I understand what you are explaining but I understand the concept. What "line" are you following?

    the line on the schematic once you identify it...

    the "alligator clip and wire" tool is used to diagnose the problem once you have identified the circuit... it doesn't remove the need to be able to read the schematic and figure out where/what you need to jump...

    #19 5 years ago
    Quoted from ccotenj:

    @schertz... ooo, that's a tough one... since "sing along" is at the top of my list, and a pitch and bat isn't far behind it, those would tempt me... but cowpoke would be cool too...
    you could always work on all 3 at once...

    I also have a Chicago coin Bronco, doozie, Fairway, a puck bowler and a gun game in the que.

    #20 5 years ago
    Quoted from SchertzPinball:

    I also have a Chicago coin Bronco, doozie, Fairway, a puck bowler and a gun game in the que.

    given my lack of focus, if i had that many games ready to work on, none of them would ever get done... they'd all be started though...

    #21 5 years ago
    Quoted from ccotenj:

    given my lack of focus, if i had that many games ready to work on, none of them would ever get done... they'd all be started though...

    I hear you. One of my Sing Alongs I took apart the topside of the playfield over 4 years ago and have not touched it since. I also have a long list of solid state games in the que as well. I think I've started on 3 games and haven't got back to them, but I keep starting on different games.

    #22 5 years ago

    Be like a postage stamp: stick to one thing until you get there.

    #23 5 years ago
    Quoted from DirtFlipper:

    Be like a postage stamp: stick to one thing until you get there.

    I like that. I've gotten better at finishing games once I start them. I just seem to start the next game before going back to one I've already started. The latest game usually gets my attention easier.

    #24 5 years ago
    Quoted from SchertzPinball:

    I hear you. One of my Sing Alongs I took apart the topside of the playfield over 4 years ago and have not touched it since. I also have a long list of solid state games in the que as well. I think I've started on 3 games and haven't got back to them, but I keep starting on different games.

    i do not feel nearly as bad about letting my magic city sit for 6 months in a partially done condition now...

    it's more fun to start on a different game than to do the "hard parts" on another...

    Quoted from DirtFlipper:

    Be like a postage stamp: stick to one thing until you get there.

    i like that, and need to learn it... not just with pinball machines either... i have a jukebox project that has been sitting for years...

    #25 5 years ago

    My ball bowler has been in the project stage for 5 years. I also have a 1937 Wurlitzer Skee Ball that has been partially restored for about 3. I hope to get to them finally this Summer if my wife doesn't keep me distracted with house projects.

    #26 5 years ago
    Quoted from SchertzPinball:

    The latest game usually gets my attention easier.

    aint this the truth

    --Jeff

    #27 5 years ago

    Gottlieb is big on relay abbreviations. That was my difficulty at first, keeping them all sorted in my thoughts as I solve a problem.
    What I did at first was a bit time consuming but effective.
    Suppose I had a reset problem which I believed was associated with the AX relay. I'd scan to file or copy the schematic then locate all the switches associated with the AX and rename any abbreviated relay I got confused with and mark it on the schematic copy. It was slow and cumbersome but now I don't have to do it anymore.

    Another thing to remember is the major function of score motors is to manage the timing for the game. Things usually happen in a specific order. Keeping this in mind can help to understand different but interacting circuits, and there's usually a timing chart or diagram of the score motor on the schematic.

    #28 5 years ago

    Good thread Chris.

    I have picked up on reading a schematic from some of dirtflippers posts and others that contribute. If we could all get into a habit of posting the section of the schematic associated with the problem at hand it would be great. That's where I learn a lot. Learning schematics reminds me of starting out in your job when you're brand new. The more you work on problems with pins and use the schematic to find them, the better you become. I also like Chris's action/reaction post above - that's what I need help on.

    #29 5 years ago

    @steve... i like that idea of labelling everything... and that's a good point about score motor timing...

    @hoov... thanks... i agree strongly with the "post a snippet"... that way all of us can lurk/participate and practice/learn...

    good analogy on the "new job"... this really is "repetitive practice learning"... the more you do it, the better you get... and you start recognizing patterns in the logic, which also makes it easier... once you trace 3 or 4 circuits that use the "100 point relay" (for example), you end up not having to trace entire circuits, because you already "know" what happens when that relay fires...

    i was a computer programmer by trade... once i started to think of the relays as subroutines that got called, and those subroutines simply manipulate true/false variables and call other subroutines, the "logic" of how a machine worked came together for me... actually translating that logic to the schematic wasn't/isn't so easy...

    #30 5 years ago

    Yes Chris, helps to think of EMs as analog computers for sure!

    #31 5 years ago
    Quoted from AlexF:

    My ball bowler has been in the project stage for 5 years. I also have a 1937 Wurlitzer Skee Ball that has been partially restored for about 3. I hope to get to them finally this Summer if my wife doesn't keep me distracted with house projects.

    you better get that skee ball done befor i make my way to wisconsin someday... otherwise, it's coming back to the swamps with me...

    #32 5 years ago
    Quoted from stashyboy:

    Yes Chris, helps to think of EMs as analog computers for sure!

    yup... they are nothing more than an event driven application specific computer...

    #33 5 years ago
    Quoted from stashyboy:

    Yes Chris, helps to think of EMs as analog computers for sure!

    I've said this before about bingo machines. Don Hooker was a genius! They truly are analog computers.

    #34 5 years ago

    If I had a decent pair of eyes or could find my glasses then I would use a schematic. I usually just wing it though.

    #35 5 years ago
    Quoted from o-din:

    If I had a decent pair of eyes or could find my glasses then I would use a schematic. I usually just wing it though.

    I hear ya man, it sucks when your eyes go. I was wearing two pairs of glasses today working on my latest pin. Reading a schematic usually requires glasses and a magnifier. This is especially true after several adult beverages!

    #36 5 years ago
    Quoted from jrpinball:

    I hear ya man, it sucks when your eyes go.

    Yep, I can see for miles and miles, but that small stuff right in front of my face is getting blurry, a little blurrier after a couple beverages. I used to read those automotive schematics like a champ, so I understand these fully, but now we are looking at 50 year old print that wasn't always that great to begin with. But I do break out the magnifying glass and try to make sense out of it when I have to.

    #37 5 years ago
    Quoted from way2wyrd:

    aint this the truth
    --Jeff

    So much for Cowpoke being next. The gun game made it into the garage tonight so I could use the trailer for TPF.

    #38 5 years ago
    Quoted from o-din:

    If I had a decent pair of eyes or could find my glasses then I would use a schematic. I usually just wing it though.

    you ever find that switch adjustment tool?

    #39 5 years ago
    Quoted from SchertzPinball:

    The gun game made it into the garage tonight so I could use the trailer for TPF.

    the midway?

    #40 5 years ago
    Quoted from ccotenj:

    you ever find that switch adjustment tool?

    No, but I bought 5 new ones.

    #41 5 years ago
    Quoted from o-din:

    No, but I bought 5 new ones.

    on the (too many) occasions i've had to search for mine, i often consider putting one in the cash box of every machine...

    thinking about it, it would be kind of neat to have a little "tool kit" for every machine (like you used to get with a car)... especially since my "pin room" isn't near my "work room" (and my work room on the best of days can be described as "disorganized"... )... for less than 20 bucks you could acquire every tool you need for 95% of repairs... couple screwdrivers, couple nut drivers, set of picks, little flashlight, adjustment tool and flexstone... put them in a cheap plastic box and toss it in the cash box...

    no more searching for tools in the middle of a repair... that is an appealing thought... even if the idea itself is a bit excessive...

    #42 5 years ago

    @o-din... VERY well played with the new avatar...

    #43 5 years ago

    I aim to please, you young whipper snappers!

    #44 5 years ago

    Yes, Trophy Gun. It might be easier if Justin does his at the same time. They are already next to each other in the garage.

    #45 5 years ago
    Quoted from ccotenj:

    the line on the schematic once you identify it...
    the "alligator clip and wire" tool is used to diagnose the problem once you have identified the circuit... it doesn't remove the need to be able to read the schematic and figure out where/what you need to jump...

    Sorry should have been more clear, the line that the non-working item is on?

    Take this schematic (just using this as an example), say coil B is not energized - are you simply referring to switches QB, C and Trough Switches and of course the other branch through switch B and so on.

    Of course this would also have to assume the game is in the sequence where coil B should turn on - that is to say jumper on, activate the would be playfield item, no difference, move jumper to next switch in line and repeat.

    DC_schematic_a.jpg

    #46 5 years ago

    ^^^

    yup, you got it... find line, jump switches...

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