(Topic ID: 221624)

WMS Comet System 9 special solenoids

By lpnsocal

1 year ago

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  • 29 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by lpnsocal
  • Topic is favorited by 2 Pinsiders


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    pg 38 Sys 9.pdf (PDF preview)
    pg 37 Sys 9.pdf (PDF preview)
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    #1 1 year ago

    All special solenoids( controlled by K1 relay) are live/grounded between games. I guess the K1 controls the ground and allows all the switches to fire those non MPU controlled coils. From my internet searches I've gleaned that this relay is supposed to shut off at game over. If this is correct what is allowing the K1 to stay activated and whats a good way to test.

    Thanks for the assistance as I muddle through my learning curve.

    #2 1 year ago

    That's not how the special solenoids work. They're controlled/disabled via logic chips on the MPU. The K1 relay (on the MPU?) controls just the flippers, which are the only non-MPU coils. Are your flippers also staying active?

    The flipper relay and the special solenoid logic chips are controlled by the same signal, EN, which comes from CB2 (pin 19) of the U4 PIA. It then goes through U6 (NORed with the blanking signal), U58 (inverter). That signal is sent to the logic chips, and also goes through U7 (another inverter) to reach Q86, which controls the flipper relay. See sheet one of the schematic (page 34 of https://www.ipdb.org/files/548/Comet_manual.pdf), bottom corner:

    Capture (resized).PNG
    #3 1 year ago

    Thanks for reply. I have seen this schematic in my downloaded manual, and can understand and recognize some of the components and purposes. Direction of data/power still confuses me. I think I understand that the chips handles data signals to the work horse components(transistors and the like.)

    All my pops, slings and flippers can be fired via pf switches between games w machine powered on. Since these appear to be all the special solenoids and after reading a bit (see below,) I concluded(erroneously?) that K1 controls all special solenoids grounds. Attached are two of my source pages from WMS trouble shooting guide for Sys 9. They are pages 36 and 37 not as I labelled.

    Give me a little info and I'm dangerous, but at least I try and test first. I do have a logic probe, and a multi m as well.

    pg 37 Sys 9.pdfpg 38 Sys 9.pdf
    #4 1 year ago

    since there's that bar above the EN that usually means low = enabled, so I'd assume during normal operation (during a game), pin 19 of the PIA would be low, and during game over it should go high.

    Since both the flippers and special solenoids are working I would expect the error to be with U58 or before, so check the inputs and outputs of each chip between the PIA and U58.

    During game over, U4-19 should be high, U6-13 should be low, U58-6 should be high, if I'm reading this right. If you can check all those places in and out of game, and see which doesn't change, that should point to the issue

    #5 1 year ago
    Quoted from zacaj:

    Since both the flippers and special solenoids are working I would expect the error to be with U58 or before, so check the inputs and outputs of each chip between the PIA and U58.

    Not sure what between PIA and U58 means. I found both U58 and U59 on the board, and I'm assuming one side is inputs and other is outputs, so I can check the pins hi/low status during game and not. Also I can check U4-19, U6-13 and U58-6 per instruction.

    #6 1 year ago
    Quoted from lpnsocal:

    Not sure what between PIA and U58 means. I found both U58 and U59 on the board, and I'm assuming one side is inputs and other is outputs, so I can check the pins hi/low status during game and not. Also I can check U4-19, U6-13 and U58-6 per instruction.

    Between the two meaning there's a chain of chips that are connected. The pia is the beginning, and u58 is the end.

    #7 1 year ago

    I connected tester leads to TP 1&2 for 5v and gnd, and figured I should use the TTL setting. hopefully that was right, it was same setting i've used before checking chips. Results were U4-19: in L ,out H, U58-6: L and L, U6-13 L and L. I also decided to check some of the other pins on the specified chips and was getting some square pulse readings that I've never seen before. Most of the rt side 21-36 of U4 and a lot on both sides of U58. Is that significant?
    Also, when machine is first turned on the 3 pops fire in quick sequence. I don't have another Sys 9 so don't know if it's normal.

    Thanks again for direction

    #8 1 year ago

    What do you mean "in L, out H"? It's only one pin? Also was this during the game or during attract mode?

    I don't think they should fire on game start

    #9 1 year ago

    in= in game, out =out of game(attract mode) L = low, H= high for logic probe reading
    Square pulse indicated by both high and low lit with pulse light lit also

    I just double checked w PF up, and it appears all but flippers, kick out coil, drop target reset coil fire on power up. I have seen machines do a reset at game start up, clearing any stray balls etc.. but I don't recall on power up.

    #10 1 year ago

    Ah, okay. U6-13 (the output of that NOR gate) should be the opposite of its input (which is attached to U4-19). Since it's not changing, then U58-6 (which is the inverse of U6-13) is also not changing. Either U6 is bad, or (less likely) U58 or something else is pulling the signal low.

    #11 1 year ago

    Forgive my curiosity., Does that mean all sq pulses are inconsequential? U6 is the only chip that didn't have them. The little ICs are pretty cheap and fairly easy to replace, so I'm cool with that. U4 is another animal.

    Additionally, could this be related to the coils firing on power up? Note: Per quick investigations, it appears that it is not unusual for this to happen on start up, tho I'm reluctant to write it off as we're working in that neck of the woods.

    #12 1 year ago

    U6 looks like it's just used for special solenoid stuff, so unless you were hitting special solenoid (specifically special solenoids 1,5,6) switches on the pf you wouldn't get much IO on it.

    U6 being bad (or any other chip in this circuit) would also prevent the blanking signal (which keeps everything disabled till the CPU boots) from disabling the special solenoids, so any noise on the data lines before everything is booted could affect them

    #13 1 year ago

    Thanks, I kinda understand My confusion goes back to the direction of data and current flows in these schematics so.... I plod on slowly in my learning curve.

    Ok, So I'm going to replace U6 and likely U58 while i'm getting dirty. Hopefully, i have thoseand the sockets or it's another GPE order.

    Thanks again, I'll respond as I move forward.

    #14 1 year ago

    Ok, I found that I have some ICs that may work. U6 calls for a 7402, I have 74LS02. U58 calls for a 7406, I have a SN7406N.

    Can I use these as replacements?


    #15 1 year ago

    The 7406 yes. Not sure about the 7402. Probably, but I'm not too clear on the letters in the middle.

    #16 1 year ago

    Ok, I found this while searching the internet for substitute for 7402 and it's a Pinside post from Ed at GPE.

    Quoted from G-P-E:

    Just to touch on this topic for future users.
    -NO- you cannot always replace 7402's with 74LS02's.
    There are several occasions where there is a high current load on the 7402. The 74LS02 cannot provide nearly as much current as a 7402 can.
    There is no simple answer to this one. In many cases, you can replace 7402's with 74LS02's or the newer 74HCT02's. This is whenever the load on the '02 is light such as only driving a couple other logic IC's. But, when driving high current loads (e.g. Williams Solenoid drivers), you must use a high current device such as another 7402 or 74S02 or 74F02.
    When in doubt - ask here. But make sure you also mention where the part is used in addition to the part number.

    I guess I get me a plain old 7402. Will report back upon installation.

    3 weeks later
    #17 1 year ago

    Well finally back with an update. I took some time off from this conundrum to let my sanity recharge. After finally ordering up the parts from GPE ...and waiting for delivery, I popped the new ones, LS7402 and 7406N into the new sockets I had perviously installed. Initially, there was nothing at all going on in the Solenoids circuit. So I immediately checked the fuses and two were blown, F1(high voltage) and F2(solenoids), tho not sure what happened there, but something did! Anyway, I replaced them both and fired it up, but no special solenoids at all. Worse off than before as they were were working all the time prior. So I swapped out each U6 and U58 to see if maybe I got a bad one and no change. Last thing I did was check the pins with the logic probe. U4 out of game High, and in game Low. U6 out=L, and in = L, U58 out=H, out=H.

    At this point I walked away for a while to gather myself(sorta.)

    Now, clearerish headed , I'm trying to figure how I went backwards in this repair. Please Save me from myself...and this machine!

    #18 1 year ago
    Quoted from lpnsocal:

    U6 out=L, and in = L, U58 out=H, out=H

    Which pin on each of those?

    #19 1 year ago

    oops, same ones as before, U6-13, U58-6, U4-19

    #20 1 year ago

    Can you check U6-11 and U6-12 as well?

    #21 1 year ago

    Ok, U6- 11 out=H, in=L
    U6-12 out=H, in= H

    #22 1 year ago

    I'm not 100% on this, but by my understanding U6-12 should be low normally, regardless of whether you're in a game or not. Can you check pins 8+9 of U59? That should be inverting the blanking signal. Should be high on 9 and low on 8 (8 is connected to U6-12), both pins 11+12 of U6 need to be low for the special solenoids to enable.

    #23 1 year ago

    My experience is typically that the U6 or U7 (U50 on system 11's) is damaged and this damage is usually caused by a bad special solenoid coil/transistor. When a special solenoid locks on I find it usually takes out the TIP102, the fuse, the coil and about half the time the TTL chip that turns on the transistor. On system 11's where I usually see this One TTL chip supplies the signal to 4 of the special solenoids and the other supplies the signal to 2 of the special solenoids, then one of the extra gates on that second chip is used for the enable signal for the flipper relay and special solenoids System 9 looks just a touch different with U6 handling 3 special coils and an enable and U7 also handling 3 specials and the enable.

    7406 Is an inverter gate (inverts low to high and vice versa)
    7402 is a NOR gate (low and low are inverted to high, all other combinations are low)

    The Enable signal (En with a line over it) should be HIGH in attract mode and should go low whenever a game is started or when the game enters the diagnostic mode. This is at U6 pin 11.
    The Blanking is low for a few seconds at start up and is then high after a second ( this gets inverted to low at U59 pin 8 ) and hits U6 at pin 12 and is low at all times

    So at attract mode the inputs at U6 11 and 12 are high and low respectively and the output at 13 is low. Then you start a game and 11 and 12 are both low so the output at 13 goes high. U58 then flips the signal so the output on U58 goes from high to low which then activates the other NOR gate at U7 so that the flipper relay is active. The low output on U58 is also now used on U6 and U7 at all the special solenoids and when combined with the low from each direct solenoid switch will activate the solenoid coils.

    If U6 was broken before it might have been STUCK with a high output regardless of the input. If the new chip now has all the special solenoids disabled during game play then double check the inputs into U6. Pin12 is the inverted blanking and should ALWAYS BE LOW Pin 11 should be high during attract mode and go low during game play. If Pin 12 is high instead of low there might be a blanking issue with the MPU board.

    My Forte is with System 11 and 9 is 90% similar but uses different numbers for the chip locations and some small differences. Like the blanking only uses 1 other gate on system 9 (U41 a 7404 ) and this chip appears to ONLY be used for the one gate. ON system 11 they used some gates from the special solenoid chips on the blanking so I see alot of damaged blanking circuits on system 11C games at the special solenoid chips

    #24 1 year ago

    Well Thank You'z, that's a whole lot of info guys. I'll read it at least 3 more times, to make sure I get my head good and spinnee. Then, I'll test all mentioned U pins in attract and game, and report back.

    #25 1 year ago

    For what it's worth here are the latest results,
    U59-8 Out of game= H and In Game = H (problem..?)
    U59-9 Out =H and In = H

    U6-11 Out = H and In = L
    U6-12 Out =H and In = H

    Additionally: Upon game power up saucer ejects fire and upon game start ball trough eject fires(normal actions I think.)

    Lastly and maybe irrelevant, During attract all lamps either on or slow flashing depending on which lamps, but on game start there are a ton of lamps staying on. I don't remember this occurring in my original assessment but it has been a couple weeks of hiatus(?). Some obviously should not be on, others I'm not so sure (literally more than half of the lamp matrix ) I mention this not to muddy the thread but as a possible correlated issue or?

    I'm getting ready to pull the board again, and recheck continuity/traces but part of me says waste of time. If I'm getting signals/pulses/blanking to the various U pins, I've got my continuity, correct?

    Thanks for the continued lessons/help!

    #26 1 year ago

    U59-8 should be the opposite of U59-9. It shouldn't change depending on whether you're in or out of game (it should change stay the same once the CPU has booted). Since they're both the same you've got an issue, probably the chip itself.

    #27 1 year ago

    So......replacing U59 is the next step?

    #28 1 year ago
    Quoted from lpnsocal:

    So......replacing U59 is the next step?

    Unless it's not getting power or something. It's weird that it's failed now but everything normal those two pins should be opposites

    #29 1 year ago

    Ok...., I'm tip toeing around as it appears the replacement of U56 has solved the final leg of special solenoid issue! Everything comes on when it should and shuts off as well. And as a a side Bonus.....the lamp issue is gone! I can only guess I may have had a connector askew as nothing but U56 and connectors were touched.

    All in all, I learned some more and really appreciate the help and patience.


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