First Unplug the machine right now before you fry something or make the machine worse without doing some pre tests.

Now go to these two websites and read on how to proceed in diagnosing and fixing that machine. This will save you time and money.

http://www.pinwiki.com/wiki/index.php?title=Bally/Stern

http://techniek.flipperwinkel.nl/ballyss/rep/index1.htm

If you get stuck post back.

Mike

Start by isolating and rebuilding the power supply/rectifier board.

Then rebuild ALL connectors on ALL boards. This is absolutely mandatory and absolutely time-consuming and tedious.

FIRST, clip that battery off of the MPU! NOW!

Can't stress this enough. Looks like your MPU is still undamaged by battery corrosion--which is very lucky--usually those old, factory installed batteries have eaten up the MPU by now. Clip it off right now, before you do anything else, and you'll save yourself so much trouble.

The MPU will work fine without the battery, it just wont save any settings when powered off. After you get the game working, you can install one of the other 'battery replacement' solutions for saving memory (like backup memory cap, NVRAM, or off-board batteries, etc), or leave it off if you don't care about saving the settings.

That MPU looks nice. Cut that time bomb off right now

Yep.
Snip, snip... done.

The boards in that machine actually look quite nice. At that age, you may have a few connector issues and may need to repin a few plugs. Might need to recap the main power board as well. While at it - pay particular attention to a few wires added to the solenoid/driver board in the links posted by packie.

Once you get machine running, you may need to recap sound board as well.