Yea, classic battery corrosion problem. Also make sure all the balls are in the game. If you get 7 flashes on the mpu and no boot it's usually because the ball switches are not registering.
Zabs list is spot on with a 'barn find' like this.
You can find Cap kits on ebay for these games. Assuming the battery damage is not fatal caps and solder reflows should get you going.