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(Topic ID: 222344)

MPU 100 Missing Capacitor


By oldschoolbob

2 years ago



Topic Stats

  • 9 posts
  • 5 Pinsiders participating
  • Latest reply 2 years ago by KenLayton
  • Topic is favorited by 1 Pinsider

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#1 2 years ago

I’m working on a Stern Lectronamo. It wouldn’t boot in the game – missing 5 volts at the MPU. I have 5 volts at J4 so I pulled the board out and tested it on the bench. It booted fine. I need to replace the headers so I was looking it over so see what else needs to be done. That’s when I noticed that C80 is totally missing!

This board has been worked on before but I see it needs a lot of help. I just thought it was strange that it boots with missing parts.

Bob

IMG_2404 (resized).JPGIMG_2405 (resized).JPG
#2 2 years ago

That's a picture of a Bally -17 MPU board. Capacitor C80 should be a .01 uf @ 100v.

#3 2 years ago

You mean it's NOT the original board? I'm shocked. Just kidding - seldom do I find a game with the original boards. But how can you tell it's Bally and not Stern?

#4 2 years ago

C80 missing is not a big deal, it's just a filter cap to clean up the 5v supply slightly. There's 8 of them around the board so if one fails not much happens.

#5 2 years ago
Quoted from oldschoolbob:

But how can you tell it's Bally and not Stern?

M100 just look different. Traces with rounded edges, darker colored pcb and other stuff

#6 2 years ago
Quoted from oldschoolbob:

You mean it's NOT the original board? I'm shocked. Just kidding - seldom do I find a game with the original boards. But how can you tell it's Bally and not Stern?

If it hadn't been sanded off to get at the corrosion there'd also be a part number on the bottom right

#7 2 years ago
Quoted from oldschoolbob:

You mean it's NOT the original board? I'm shocked. Just kidding - seldom do I find a game with the original boards. But how can you tell it's Bally and not Stern?

All the Bally boards are clearly drawn using CAD (Computer Aided Design) and all the traces are straight lines with angular turns and everything nicely lined-up. Stern actually stole the board-designs, re-drawing them by hand so you get swoopy/curvy traces instead. Because the designs were basically copied (and Stern did_ get sued by Bally over this!) almost all the boards are direct, drop-in compatible, the major exception being the MPU-200 vs. AS2518-35 (though these boards can easily be converted either direction).

#8 2 years ago

Stern boards are colored dark blue whereas Bally boards are green.

#9 2 years ago

Stern boards are colored dark blue whereas Bally boards are green.

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