(Topic ID: 293288)

Bally driver board repair issue

By Ballypalooza

5 months ago

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  • 12 posts
  • 4 Pinsiders participating
  • Latest reply 5 months ago by Ballypalooza
  • Topic is favorited by 1 Pinsider


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    Darlington (resized).jpg
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    1796A2F9-C067-4224-B857-C3AC6F3C7AFA (resized).jpeg
    7A41243C-949E-475C-B835-3239AF430E36 (resized).jpeg
    SDB_Coil_Drive_Voltages (resized).png

    #1 5 months ago

    I’m working on a Bally 2518-22 SDB for a friend. He brought over a box of crap and would like me to see what I can do. I have very little experience and knowledge, but would dive in and try. I’ve been able to get 4 up and running 100% and that feels great. BUT, he has one that locks on ALL playfield coils at power up and blows playfield fuse. It came in that way. I’ve rebuilt J3 andJ4 with new pins. Checked tip102 transistors and they measure normal. Thought it might be the U2 chip on the board, it was nasty looking. Pulled one off another parts board and no change. So what would lock on all coils at power up? All driver board test points are within range.
    Thanks for any help.

    #2 5 months ago

    Can you post some pictures of this board - let's see what you're dealing with. Maybe something peculiar will stand out.

    For all coils to lock on at power-up you're looking at multiple failures.

    Disconnect connectors J1, J2, and J5 from the solenoid driver board. If your knocker is in the head, disconnect it too. This will isolate all solenoids from the driver board.

    Measure the following locations on the solenoid driver board - these are the circuit drive for the flipper enable relay. In attract mode the relay should be off. Let us know what you measure.

    SDB_Coil_Drive_Voltages (resized).png

    #3 5 months ago

    Hey Quench, thanks for offering the help.
    The board is on my homemade test bench. I unplugged J1,J2, and J5. Turned on power and system booted up in attract mode.
    With game in attract,
    U4 pin 3. 5.08v
    U4 pin 2. 2.06v
    CR15 non 2.06v
    CR15 banded. 1.31v
    Q15 tab. .59v

    With game started,
    U4 pin 3. .49v
    U4 pin 2. 2.05v
    CR15 non. 2.06v
    CR15 banded. 1.31v
    Q15 tab. .59v

    Hope this makes sense. Here’s a couple pics. I’m headed out of town for a couple days, but will be back to respond with anything you recommend. Thanks much, Damon

    1796A2F9-C067-4224-B857-C3AC6F3C7AFA (resized).jpeg7A41243C-949E-475C-B835-3239AF430E36 (resized).jpeg
    #4 5 months ago
    Quoted from Ballypalooza:

    Hope this makes sense.

    Sure does.
    The readings you have on U4 indicate it's bad. If you're familiar reading the schematics, U4 is a CA3081 transistor array chip that simply contains seven transistors.
    U4 pin 3 is the base of a transistor. It must never go above 0.9 volts. Your reading was 5 volts indicating that pin has internally gone open circuit. This results in that transistor being unable to switch off the flipper enable relay.

    When the transistor arrays fail, it's usually just a single transistor failure in the chip. For every single coil to lock on means there was some catastrophic event to damage all the transistors in the arrays, maybe the solenoid voltage got shorted to the 5V logic supply.

    These are all the base pins of the three transistor array chips on the board. Any pins that measure higher than 0.9 volts means that chip is bad.

    U1 pin 3
    U1 pin 6
    U1 pin 8
    U1 pin 10
    U1 pin 11
    U1 pin 13
    U1 pin 16

    U3 pin 3
    U3 pin 6
    U3 pin 8
    U3 pin 10
    U3 pin 11
    U3 pin 13
    U3 pin 16

    U4 pin 3 <--- You already measured this one as bad
    U4 pin 6
    U4 pin 8
    U4 pin 10
    U4 pin 11
    U4 pin 13
    U4 pin 16

    #5 5 months ago

    While you are at it, replace those original large filter capacitors. Look for Bally power supply cap kits like the deluxe kit at BigDaddy and swap them out.

    #6 5 months ago

    Just two caps so no real need for a kit for that one.
    Get a screw terminal cap for $9 and high voltage axial cap at $5 and call it good.

    #7 5 months ago

    Thank you for your help. I will work on changing U4 tonight and report back. I have done new caps on all the boards with originals existing.
    Honored to have the best offering advice. Quench, Big Al, and Ed!! Trifecta.

    #8 5 months ago

    Ok. No finish line yet for me. chip U4 change went well. Desoldered U4 off parts board and set onto SIP pins. Straightforward. Plugged in all connectors with fresh playfield fuse and powered up. I can’t confirm that ALL coils lock on, but it sounds like many do and blows playfield fuse again. Brought out the multimeter.
    Game in attract mode flipper relay off.
    U4 pin.3. .89
    U4 pin 2. .35
    CR15 non. .35
    CR15 banded. .01
    Q15 tab. 45.1

    Game mode relay on
    U4 pin3. .51
    U4 pin 2. 2.03
    CR15 non. 2.03
    CR15 banded. 1.3
    Q15 tab. .6


    40B8BBF4-B3C2-467C-B964-363103C71724 (resized).jpeg
    #9 5 months ago

    Your flipper enable relay voltages all look good now.

    Time to check the voltages on all those other pins I mentioned that control all the other coils.

    #10 5 months ago

    We have a winner!! Using your chart, I checked U1 pins and they were good. Then U3...too high. Swapped out and all is good now. I also changed out C23 cap and tested on my Paragon. It’s a 100%.

    So, I want to try to wrap my head around this the best I can. I wish I had been taught how to read a schematic rather than years of wasted Spanish. If I have a coil not functioning, and I briefly ground the correct tab and it fires the coil, that confirms connection to that coil is good. Then test the transistor, diode and resistor. If they test in line, then check U1-3-4 pins to see if a transistor is bad on one of the chips. What does U2 do? If U1,3 and 4 have 7 transistors each, that’s enough to cover the whole game.

    #11 5 months ago

    Trying to keep the explanation simple as to what U2 does but it's not easy.

    U2 is used to select one of the 15 momentary solenoids. Due to how it is implemented, U2 can select only one momentary solenoid at a time. These 15 momentary solenoids are controlled by transistors are within U1, 3 and 4: Seven transistors within U1, Seven transistors within U3 and one transistor within U4.

    Of the seven transistors within U4 -- one is controlled by U2 as a momentary solenoid control, four of the transistors are used are controlled by the "Continuous Solenoid Data" lines from the CPU board and 2 of the transistors within U4 are not used.

    The 74154 decoder (U2) is not able to switch enough current to the final output transistors. So the CA3081s and their respective 120 ohm resistors provide additional current to the final output transistor -- the SE9302s.
    Actually, the 120 ohm transistors provide the required current to turn on the output transistors, the CA3081 is responsible for turning the power 'off' to the output transistors.

    Also note that Bally has drawn the output transistors (SE9302s) improperly. These are actually "Darlington Pair" transistors which means each of those SE9302s has two tightly coupled transistors internally. So each solenoid output is actually controlled by -three- transistors. One within the CA3081 and a pair of transistors in each of the final output transistors. Had to throw that in there to add to the confusion factor. Shown below is a 'Darlington Pair" transistor.

    Darlington (resized).jpg
    #12 5 months ago

    Yes Ed, thanks. That explication was gold! Till that last paragraph. Haha. I really think that this is becoming much clearer and I will be placing a order with you soon.
    You guys are awesome. Thank you so much.

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