You'll probably need to give those boards the going over. I'd suggest bulletproofing it like vid's guide days to do.

Yes, removal of the batteries changes all the settings back to factory default, unless the game is powered on while you remove and replace. Free play is not a default setting.
Do not replace the batteries. There is obvious corrosion that needs to be dealt with. This will get worse until it is cleaned up properly.
Unless you really know what you are doing with board repairs you should send at least the MPU and driver boards out for rebuild.

Good luck!

Hi Deedubbs -
I think you have a bit more battery corrosion damage than you may realize. I see a lot of green, particularly in the interconnect plugs. You really should get the MPU/Driver boards before you can troubleshoot anything else.

Assuming that the credit-issue is not on the boards, and is mechanical, you could have a leaf-switch stuck closed in your coin door.

Williams system 3-7 games are generally good games to have. Follow Vid's bulletproofing guides to repair/upgrade the MPU & driver boards- you will not be sorry. Be sure to also address the power supply and sound boards, the flippers, and drop targets (if it has any) Check over all playfield solonoids and all connectors too. Think I've covered the basics-if I missed anything/given any bad advice please correct me folks.

OP. The chances are you have multiple issues with your pin. The chip above the battery holder has been affected by the leaking battery as has the 40 pin connector. The missing segments on the displays is another issue altogether.

If you plan to fix the pin yourself you need a methodical approach to fixing your problems which Vid's guide will give you.

Otherwise send the boards out for repair.

Either way good luck. Tri Zone was my first pin and is pretty good ☺ (as I'm sure you know)

There are several pinsiders who work on Williams boards. JohnWartJr, Chris Hibler and Barakandl come to mind. There are also retailers and professional service companies who do repairs on a more full time basis.
Barakandl (Andrew S.) has repaired MPUs and drivers from a couple of my Williams Sys 6/7 games for very reasonable prices. He has done great work with a very quick turnaround.
Just guessing $100-120 for rebuild of the MPU and driver boards. It will depend on how bad the corrosion damage is though.

I would suggest buying an old vcr and practicing your solder skills. If you are going to own a pin, you'll want to learn how to fix them, as it can get costly if you always have to have someone come fix it for you.