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Pinball Flipper Logic

Discussion in 'Troubleshooting and Repair' started by TBennettcc, Sep 25, 2011.

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  1. TBennettcc


    Dec 4, 2010
    Hey there, everyone! Long time no see! I've been busy trying to get into the US Air Force as an officer. We'll see how that goes...

    Anywhoo, a friend of mine has a pinball table (Black Knight 2000, by Williams, for those interested.) I don't know if any of you are familiar with pinball flipper circuits. This is the first time I've worked on one. (Schematic attached). Each flipper has two coils. One is a 'power' coil, the other is a 'hold' coil. The power coil is designed to actuate the flipper quick and hard. After the flipper has traveled all the way out, it toggles a switch to disengage the power coil, and the holding coil should be enough to hold the flipper in place until the flipper button is released.

    The upper-right flipper is actuated by a double-pole, double-throw switch (the end-of-swing (EOS) switch for the lower-right flipper.

    Here's the problem I'm having: the lower-right flipper and the left flipper are both working perfectly. However, whenever the right flipper button is actuated, the upper-right flipper only flips, and then goes back down. This tells me that the power coil is getting power. What I don't understand is #1) how there can be power to the power coil, and yet not to the holding coil of the upper-right flipper, and #2) why the flipper powers only once, and then falls. By my understanding of the logic for the circuit, the flipper should kick back up every time the end-of-swing switch is deactivated?

    I'm having trouble understanding the logic, and where any potential problems might be.

    The power coil is getting power, so we know the circuit is complete at least to that point. Could the holding coil be bad? I measured the continuity (in-circuit), and it seemed to be good. I also measured against a known-good brand new coil, and seemed to come up with the same numbers.

    I can switch out the coil with a known good one, but I'd hate to go through all that work and then find out it was something else. (Did that once already. The upper coil wasn't even working before, so I switched out the coils. Didn't work, so I changed them back. Then I found a broken wire at the EOS switch for the bottom-right flipper. That got me to this point.)

    Any help on this is much appreciated.

    Attached Files:

    • scan.jpg
      File size:
      71.6 KB
  2. shrtrnd


    Jan 15, 2010
    I don't have your pinball machine.
    MY pinball machine is wired so that the lower flippers STAY up when depressed, and
    the upper flippers are wired to flip ONLY when the button is depressed, and then it
    deliberately releases. I assumed it was deliberately designed that way as a challenge
    to the game.
    I didn't trace your schematic, somebody else might have a solution for you.
    Just my 2-cents worth.
    I'm sure you can make it do what you want it to do.
  3. KJ6EAD


    Aug 13, 2011
    Have you gone through the solenoid and switch tests for the relevant solenoids and switches? Have you checked the adjustment of the end of stroke (EOS) switches?
  4. TBennettcc


    Dec 4, 2010
    That's an interesting point, shrtrnd (I apologize, I see to have misplaced your name.) I have zero experience with pinball machines. The only problem I have with that, is if it's supposed to work like that, why bother to put a second coil in the upper flipper solenoid? With the amount of work that went into creating these pinball machines, I can't imagine a detail like that would be overlooked, but rather intentional.

    KJ6EAD: Yes, I stepped through the solenoid and switch tests, however, my understanding from looking at the manual and performing the tests was that the manually-controlled solenoids were not included in the test, as they can be manually triggered at any time. If I have misunderstood, please correct me.

    As far as the EOS switches, my understanding of the circuit is that after the power stroke, the power coil is disconnected by the EOS switch, leaving only the holding coil powered. If the holding coil failed to hold the flipper, the flipper would fall, dis-engaging the EOS switch, which would then re-trigger the power coil, and the flipper would oscillate. This is not happening. It very well could be by design, but I can't imagine the designers would put a solenoid with two coils there if it didn't have a purpose.

    By the way, how are you liking ham radio so far? ;-)

    Thank you both for your time.
  5. KJ6EAD


    Aug 13, 2011
    Your understanding of the function of the flippers and switches is correct. Leaf switches in pinball games have to be adjusted correctly so there's a potential problem area. On your schematic there's a "UPF interboard" that could also be a problem. The simplest explanation of the problem would be a failed hold coil on the upper flipper.

    Ham radio has been fine so far. Just a bunch of old guys talking about their antennas. :D
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