If it still has the original closed frame IC sockets, those can have broken prongs under the socket frame that you can't see. Sometimes you can carefully lift off the plastic frame and inspect the socket prongs.

It is possible to damage the IC socket by trying to inspect it like this, so don't attempt this unless you're comfortable replacing the sockets.

Yep, the Brown Scanbe sockets have to go if they are on the board still.

Bally stopped using the brown crap sockets before - 35 MPUs came out.

Not saying that it still couldn't be socket issues. The closed frame augat brand sockets are pretty terrible as well.

Replace the brown sockets with nice new machine pin sockets, making sure not to damage any traces underneath.
Then try your PIA chips and see what happens

https://pinside.com/pinball/forum/topic/vids-guide-quick-bally-driver-board-repair-bulletproofing/page/2

I'd give the whole board a good bulletproofing

When replacing the PIAs/sockets, you've got to be extra careful not to bridge the small traces between the legs of the PIA. That'll definitely keep you at 2 flashes.

nothing.... just means you bent the leg. Straighten it out and hope it doesnt snap.

I was having same problem on one board, check traces from ALL chips from the top. See on schematic where the traces goes and test it with DMM. If you find a bad trace trplace it with wire.

Wise idea. But don't be afraid to learn either. This stuff is mostly just having the right tools and getting a feel for temperature settings and how long to leave the iron in one spot. A great place to start if you are into guitars at all is with a simple stompbox kit, like an overdrive. It'll give you a good idea of whether you even want to learn this stuff in the first place.