Friday March 29, 2024

Repairing a Stern MPU-100 Pinball Board With Battery Corrosion Damage

Step 2: Cleaning Up Corrosion
The first thing I did was remove the battery using wire cutters on the battery leads -- I wanted that sucker gone!  Next, I started chipping away at some of the bubbled solder mask on the outside of the board.  There's large ground areas on the board on the bottom and in the middle.  In the picture below you'll see the ground areas on the back of the board that I scraped / sanded the solder mask & corrosion off of.  I used a combination of my fingernail (not recommended), small screw driver & pocket knife to get the worst off. I then sanded with some fine grain sandpaper -- make sure it's something like 100 or 150 grit sandpaper as Clay's guide recommends.

Stern After (Back)


Here's the front of the board after I scraped and sanded the bulk of the affected areas:

Stern After (Front)

You'll notice that there's still some corrosion at the bottom center of the board, this got cleaned up further.  I found the closer to the battery you got, the more difficult it was to remove the corrosion.  In fact, in some areas the battery acid had eaten entirely through the copper of the board.


Here's some closeups of the front of the board:

Stern After (Closeup Front)

There is still some more sanding to be done after the affected components are removed.

 

Stern After (Closeup Front)

In this picture, the capacitor on the right (underneath the U8 IC socket) is cracked, partially thanks to the corrosion.  Some of the pins on the IC socket broke right off with a light poke of a small screw driver.  Battery acid is no good for these components and you'll likely find some components that break off without any trouble at all.

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Comments:
Bally Fathom repairs
Posted 06/17/11 3:55AM by Anonymous Techdoser
Thanks for your info, much appreciated. - I'm repairing a Bally Fathom 1981 - MPU board looks similar condition to yours.