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(Topic ID: 276717)

Burned Stern MPU-200 - Saved!


By TheWiz

3 months ago



Topic Stats

  • 15 posts
  • 8 Pinsiders participating
  • Latest reply 87 days ago by TheWiz
  • No one calls this topic a favorite

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    #1 3 months ago

    This one should be interesting, wonder why it burned like that. Apparently over fused, must have shorted out the 5 volts? This from a Meteor game, maybe the meteor hit the board, lol.
    E90849F7-25DD-4BA5-9428-790BE75CEE6C (resized).jpeg

    #2 3 months ago

    Never ever seen an mpu burn up in a Stern or Bally game. Interesting.

    #3 3 months ago

    Looks like someone was trying to makes s’mores with your board.

    Time to buy a weebly-nvram mpu for $160 delivered. Just as good as an Alltek but an Alltek will run you $199 plus approximately $12 s&h.
    https://pinside.com/pinball/market/shops/1055-nvramweeblycom/01281-new-universal-bally-stern-replacement-mpu-

    #4 3 months ago

    That section of the board is where the mpu handles the coils. I'd be wary of coil voltage shorting to 5v somewhere (and quite possibly over-fused). Do the coils under the pf look okay?

    #5 3 months ago

    Not my game or board, just repairing for someone. That connector is power, pin 1 & 2 is ground, 3 & 4 5 volts and pin 6 is 43 volts. I am guessing someone got the connector on wrong and shorted 5 volts to 43 volts. If the chips are okay it won’t take much to get it going.

    #6 3 months ago

    Damn, i bet you're right. It's always connectors with these games, lol

    #7 3 months ago

    If the 5 volt got shorted to 43v, almost every chip on the board got fried.

    #8 3 months ago

    I’m going to test the chips later and see. I got my numbers backwards before. Pins 19 & 18 is ground, Pins 17 & 16 are 5 volts and pin 15 is 43 volts with pin 14 being the key. If the key plug was not in the connector it would be very easy to get the connector off 1 pin putting 43 volts and 5 volts together which would then put 5 volts to ground and you have a big mess and being over fused does not help. Considering this connector is in the hardest place to see in the back box I can see how it could happen.

    This is why you should ALWAYS check fuse values before powering up and when putting connectors on look at them first to make sure there is a key plug there, if not stick a tooth pick in it or something. Whoever did this is lucky the head did not catch on fire.

    #9 3 months ago
    Quoted from frunch:

    That section of the board is where the mpu handles the coils. I'd be wary of coil voltage shorting to 5v somewhere (and quite possibly over-fused). Do the coils under the pf look okay?

    While the j4 connector is where the solenoid signals are sent to the solenoid driver board, they are 5 volts signals. The solenoid driver board grounds the +43v that's sent to each coil directly from the rectifier board, through the under playfield fuse.

    The +43 that goes to the mpu board is just for the zero crossing signal - nothing else.

    As for the board, ouch. I'd buzz out the carbonized mess to see if it's conductive before deciding to do anything else with it. Going to be difficult to save that one.

    #10 3 months ago

    Dug out all the carbon and have my epoxy patch setting up. Tested the PIAs and memory chips, 1 PIA bad all the rest good so that is a good sign. Can’t get all the soot off the brown caps so I might just replace those, the rest cleaned up pretty good considering what it looked like before. Corrosion cleaned up, it was just starting to get to the components so some of those will need to be replaced but I am going to get it working before finishing that up.

    image (resized).jpgimage (resized).jpg
    #11 88 days ago

    Took a little scrubbing to get most of the soot off. Removed burned part of the board and filled with epoxy. Replaced sooted up caps so I could clean under them. U10 was bad and a bad U6 socket. Jumpered for 2732s and installed those. Installed NVRAM. Board boots and diagnostics work. Displays, switches and solenoids all work. Only thing left to test is to hook up the sound card to it and check that out. Not the prettiest board around but considering what it looked like before it turned out pretty good.

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    #12 88 days ago

    I really thought this was going in the trash. You did a great job bringing this back to life.
    I think I may have given up too easy on some of the boards I've replaced.
    -Mike

    #13 88 days ago

    Sound works. I’m done with this one, glad it could be saved. I’ll post a picture of the back once I get it unhooked after letting it burn in for a few hours. I had maybe 5 hours of actual work on it and around $30 in parts including the NVRAM so it was worth the effort.

    #14 88 days ago

    Great recovery, well done!

    #15 87 days ago

    Here is the back of the board.

    449837F1-2080-43EB-B584-9B9EF6499AB5.jpeg
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