Hi,

I recently picked up a Force II machine. This is my first pinball project. I have a fair amount of past experience involving electronics and soldering. The game does not boot. I'm currently sorting out my various power issues. But in the interim, I'm interested in some system80 gurus' advice on what to do with my MPU. Here's the front and back of the board:
front (resized).jpg
back (resized).jpg

For starters, the MPU<->DriverBoard was soldered together. The bottom of the cabinet contained the original connector (with broken pins), so I'm planning rebuild it and clean up the solder from the boards.

Someone previously removed the battery, however there is some damage that needs to be addressed:
bat damage (resized).jpg
What all needs to be replaced? I was thinking of doing the 2 ICs, 3 resistors, and the crystal. Do the traces need some sort of work typically?

Next, some components looked like they got hot at one point, see below. Is it something I should be concerned with?
hot (resized).jpg
hot2 (resized).jpg

Additionally in the photo above, someone soldered in some jumpers connecting PROM1 to PROM2 and drilled out some traces. Note: the jumpers do not follow the original traces. I'm pretty confused on this and what the purpose was, especially considering PROM2 is empty.

Lastly, the power connector (A1J2) is rough. The copper pad is loose and flaky. Is this something that can be fixed?
power (resized).jpg

Is this board worth fixing? Or should I be considering getting a replacement?
Any and all advice or suggestions are appreciated!
Thanks

First and foremost, thanks for the response GPE!

U6 does look different on the front of the board, so makes sense that it has been replaced. However, those 3 wires are on PROM1 and PROM2 (not U6). Any idea what they could be for? Really suspicious since some traces are drilled out as well.

I believe that is Z12 and the alcohol worked great. Good call!

Lastly, what are your thoughts on the main power conntector (A1J1). Any way to repair the flaking pad?

The impatient side of me is quick to want to replace the MPU. But ultimately, there is no rush and I'm going to try repair first and learn some things along the way. I had not seen the LISY80 project. I already have 3 RPis running things in my home (8 chime MIDI doorbell, 3d printer, and garagedoor), so the thought of controlling the pinball with a RPi (and/or Arduino) did cross my mind if all else failed. So it's really awesome to see the project in existence! But yea, for now, going to try and repair.

No worries about the mixed up parts! I greatly appreciate the help. Only corrected for clarity and my own sanity.
As for the J1 connector. Here is a closer pic:
j1 (resized).jpg

I very gently raised the copper pad for visibility. It is still attached. Is there a fix? Can it be glued back down? If so, what type of glue? I have some CA glue from RC stuff laying around.

As for re-tinning. I know the exposed copper is no-good and will corrode. I assume more than just my power connector needs to be re-tinned? How do you tell? Is it as simple as, if you see the copper, than it needs to be re-tinned? When I go to re-tin, do I use generic solder? Or is there some special solder to be used?

Thanks for all the help thus far!

Just fixed up A1J4 that had the directly soldered wires. De-soldered the wire first, fluxed + solder wick the excess solder, and then lint-free alcohol cleaning. The front cleaned up very nicely:
front a1j4 (resized).jpg

The back almost did, however, some of the pads lifted (just like that power pad):
back a1j4 (resized).jpg

Now I'm very interested in hearing how to address lifted/loose pads. Haha. After doing this, re-tinning makes more sense.