(Topic ID: 208746)

Unusual Bally -35 MPU behavior


By Ballypalooza

1 year ago



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  • 27 posts
  • 10 Pinsiders participating
  • Latest reply 1 year ago by Sonora70
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    #1 1 year ago

    Hey Guys,
    I’m having a weird issue with a board I purchased. This Bally -35 is for a Playboy game at my step father’s house. Good thing I have one in the line up that has worked perfectly for a couple years. With that fact, I have ruled out anything with the game or the connectors. I have also switched this bad board in and out several times to triple check. Same issue every time. Here we go.
    Game is not been played for an hour.
    - Turn on game and it boots fine. Looks good.
    - Hit start button, kicks out ball and starts scoring wildly for maybe 10-20 seconds. Then stops and plays fine the rest of the game. No other issues. If you shut the game off and turn back on immediately, start game, it starts and plays fine with no scoring problems.
    - if you play a game or two, turn off, then wait 30 mins, then back on. It will score wildly again.
    It’s like it has something that needs charged or is weak. Once it is done scoring wildly, it operates fine until you let the game sit and go “cold”. What do you guys think? Where should I start.
    Thanks, Damon

    #2 1 year ago

    Does the scoring stop if you unplug the playfield switch connector?

    What if you leave it on for a while before starting a game?

    #3 1 year ago

    We recently had the same problem with Gold Ball, turned out it was a wire actuator assembly that the pball would roll over when going through between the guide rails for the upper lanes. The leafs on the assembly needed a bit more distance from each other.

    FWIW

    #4 1 year ago

    Zac is spot on. Pull the playfield switch connector from the mpu. If scoring stops it's a playfield problem. Check the sling shots, over time the assembly gets loose and they fall unto the wires underneath causing a short.

    #5 1 year ago

    Ok, when “cold”, I power up game and hit start button and it scores wildly. As it is scoring I pull J3 MPU connector and it continues to score for about 20 seconds or so. Is that what you wanted me to test?
    Also when the game is cold and I turn on..... don’t start a game, and let it sit for some time, it won’t score wildly. It starts and plays normal.
    Remember the game plays perfectly with an altek and my MPU that goes in the game originally. This board I’m talking about is from another machine.

    #6 1 year ago

    Maybe one of the two 6821 chips is going wacky.

    #7 1 year ago

    Maybe one of the caps on the switch matrix lines is bad? Do a diode test from each pin on the pia related to the switch matrix to ground and see if any read different

    #8 1 year ago

    Try cold booting the game without J3 connected. If no points racking up then definitely a playfield problem. If it's racking up a lot of switch closures it would take a few seconds for the game to catch up. How many points are being added? That could narrow it down to the bad switch. I'm with ZAC on a bad cap.

    #9 1 year ago
    Quoted from KenLayton:

    Maybe one of the two 6821 chips is going wacky.

    If they are AMI chips, it's even more likely since that brand is more failure prone than other brands.

    #10 1 year ago

    Just to clarify... but I think I am understanding the the game is perfectly functional when he uses either of two other boards. It’s not a playfield issue. Unless this needs to be corrected....

    So- it sure sounds like something that is warming up and works better hot. That not a resistor... a cap maybe, as suggested, but I don’t know for sure that really makes sense. Someone has to be able to list a couple components that can break when cold but function when warm or at least energized for a while. Can this happen to a chip? I am now curious. Interesting problem....

    #11 1 year ago
    Quoted from rufessor:

    So- it sure sounds like something that is warming up and works better hot.

    It could be a component, chip, cracked solder joint, bad socket, a cut trace--any of those things will expand or contract due to temperature.

    However, the nature of the symptom can help narrow down where the problem might be.

    If you can get into diagnostics and into the switch test to see which switch is being detected, that may determine what pathway to follow on the board, if it's simply not a PIA chip malfunctioning.

    #12 1 year ago

    Few other tests.
    Removed all chips from original good board and installed them on troubled 2nd board and no change. Still racks up points when start a game from cold. None are marked AMI. Hoping that rules out the chips.

    Did U10 pin diode test. Hope this is what you specified. Also wasn’t sure which were for switches, so did 1-20.
    Pin1- .0
    2. .572
    3. .578
    4. .573
    5. .572
    6. .598
    7. .590
    8. .588
    9. .576
    10. OL
    11. OL
    12. OL
    13. OL
    14. OL
    15. OL
    16. OL
    17. OL
    18. .636
    19. .741
    20. .045

    #13 1 year ago
    Quoted from Ballypalooza:

    Few other tests.
    Removed all chips from original good board and installed them on troubled 2nd board and no change. Still racks up points when start a game from cold. None are marked AMI. Hoping that rules out the chips.
    Did U10 pin diode test. Hope this is what you specified. Also wasn’t sure which were for switches, so did 1-20.
    Pin1- .0
    2. .572
    3. .578
    4. .573
    5. .572
    6. .598
    7. .590
    8. .588
    9. .576
    10. OL
    11. OL
    12. OL
    13. OL
    14. OL
    15. OL
    16. OL
    17. OL
    18. .636
    19. .741
    20. .045

    Well, those all seem to match up. Darn.

    #14 1 year ago

    First thing you need to do is get the game straight into switch test mode when cold and watch what switch numbers the MPU board *thinks* are closed until it reports "0". These switch numbers will help pinpoint which switch strobe/return lines on the MPU board you need to concentrate diagnosis on.
    Just make sure J2 is disconnected from the MPU board before you power on so no actual closed playfield switches invalidate this cold test.

    BTW, is this a battery corroded MPU board? Can you post a picture of it?

    #15 1 year ago

    I will try this tonight, thanks. One more test to maybe give a clue. I have put the same board in question into a Bally Paragon. So starting cold, hit start, and it scores a hundred when the ball trough kicker fires. Did it twice on separate occasions and only 100 points.
    Headed to work now. Thanks for all the suggestions and ideas. Did you ever play Mastermind back in the day?

    #16 1 year ago

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    #17 1 year ago

    Thanks. Some corrosion around the edge but otherwise clean.
    The important part of the equation is the switch mode test result. What did you get?

    #18 1 year ago

    Be surprised if it even worked otherwise, but I'd double check that you have continuity all the way around the ground plane.

    #19 1 year ago

    Continuity all the way around board and up to the components.
    Just put the board back into the Playboy to recreate scoring problem. Left J2 unplugged on power up. Hit start button and it kicks out ball with no scoring. Did this twice with no scoring.
    Plugged in J2 and started game, it started scoring wildly again.

    #20 1 year ago

    I think I was able to get the fault to happen. I had all connectors attached. Fired up machine that was ‘cold’. Hit start and it started scoring. Quickly went to switch test and saw number 27 flashing in displays. After 10-15 seconds it disappeared and display went to 0. This should help hopefully. Please let me know my next step.
    Thanks

    #21 1 year ago

    In the Playboy manual, switch 27 is the miss January Target. I know it works with other boards but try unsoldering the disc cap from across the switch.

    #22 1 year ago

    Ok Cactus,
    I did notice that when I start a game and the game is scoring points on it own, the January target lights up like it’s been hit.
    Ok, I snipped the Miss January cap on one leg. Powered up and started game.... no points scored.
    So all that sounds like a bad cap on the surface, pretty easy stuff. BUT please explain why two other boards don’t have this same problem in the same game and when the questionable board is put in a paragon, it scores a few points on game start on that one too.
    Thanks

    #23 1 year ago

    If you put your multimeter on high resistance measuring scale, do you measure anything across that suspect Miss January switch capacitor (out of circuit)?

    This suspect MPU board could have some slight resistive short (commonly caused by corrosion) between switch return lines.

    Grab your multimeter and set it to read resistance. If your meter isn't auto-ranging set it to 200k ohms scale.

    With the MPU board cold, machine OFF and J2 and J3 disconnected, measure the resistance across the following pins - the readings should all be around 114k ohms:

    J2 pin 1 to pin 2 =
    J2 pin 2 to pin 3 =
    J2 pin 3 to pin 4 =
    J2 pin 4 to pin 5 =

    J2 pin 8 to pin 9 =
    J2 pin 9 to pin 10 =
    J2 pin 10 to pin 11 =
    J2 pin 11 to pin 12 =
    J2 pin 12 to pin 13 =
    J2 pin 13 to pin 14 =
    J2 pin 14 to pin 15 =

    #24 1 year ago

    J2 and J3 disconnected. Cold board.
    Measure J2 pins
    1-2. 115.1
    2-3. 114.8
    3-4. 115.1
    4-5. 114.5

    8-9. 113.6
    9-10. 114.0
    10-11. 114.8
    11-12. 115.6
    12-13. 116.4
    13-14. 115.3
    14-15. 114.5
    Anything stand out of line?

    #25 1 year ago
    Quoted from Ballypalooza:

    Ok Cactus,
    I did notice that when I start a game and the game is scoring points on it own, the January target lights up like it’s been hit.
    Ok, I snipped the Miss January cap on one leg. Powered up and started game.... no points scored.
    So all that sounds like a bad cap on the surface, pretty easy stuff. BUT please explain why two other boards don’t have this same problem in the same game and when the questionable board is put in a paragon, it scores a few points on game start on that one too.
    Thanks

    Well, the definitive test would be to install a new cap and see if the problem returns. If it does, it is unrelated to the old cap. If it doesn't, then it makes me believe it is either a connectivity issue with the strobe and return lines associated with switch 27. Or, as others have stated, a failing component connected to one or the other (resistors, capacitors etc.).

    In the strobe (output) changing state from low to high, there is a slight charge time associated with the 0.047/0.05ufd disc cap across the switch. A good cap won't effect the switch read. But as the disc caps fail, they have a tendency to effect the switch matrix in weird ways. Like with many "bullet proofing" techniques, changing all those disc caps on Target, star roll over, and thumper bumper switches is a good idea.

    #26 1 year ago
    Quoted from Ballypalooza:

    2 and J3 disconnected. Cold board.
    Measure J2 pins
    1-2. 115.1
    2-3. 114.8
    3-4. 115.1
    4-5. 114.5

    8-9. 113.6
    9-10. 114.0
    10-11. 114.8
    11-12. 115.6
    12-13. 116.4
    13-14. 115.3
    14-15. 114.5
    Anything stand out of line?

    Those readings all looks fine to me.
    Install a new capacitor on that Miss January standup target like cactusjack said and see what happens.

    #27 1 year ago

    I had a capacitor on a pop bumper on my Mata Hari that caused similar issues. Game worked perfectly with new alltek board but had issues with original board. I simply cut the capacitor and it fixed it.

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