Switch matrix problems can be on the playfield in the wiring harness, or on the boards. Always good to test and determine which it is, first.

http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Switch_Matrix_Problems

If the column works with the playfield unhooked from the CPU, you either have a broken wire, or other wiring problem.

If it's still out, check every switch on Column 2 carefully to see if any are shorted to solenoids.

It's possible that a wire broke and send voltage down column 2, which at a minimum, will damage the ULN2803 on the CPU board. I believe this chip is socketed on ST:TNG, so if so, it' not too hard to resolve. It's also possible that a wire broke off the first switch in the column, and it's no longer connected and that is why they don't work.

The switch diodes can be had at a radio shack, get 1n4001 or better. The last digit refers to the voltage the diode can handle - so a 1n4007 for example is fine, or a 1n4004.

If playfield switches column2 AND switch #21 'slam tilt' + #22 'coin door closed' + #24 'always closed' don't work, I would start searching at the CPU-board.

So cabinet and playfield switches on column 2 don't work ?!

Start with visual inspection like battery corrosion, sometimes a burnmark or hole is visible on U20 (uln2803) if it has been shorted with a power source.
Then follow the wiki-pages as JohnWartjr mentioned above, start at chapter 4.21.3 Switch Matrix Problems

Same with mine. It's a "love and hate" type thing isn't it?

Hang in there. Got mine finally dialed in, and it's fantastic.

I took a look at his machine briefly. I believe this is what is happening with the switches.

All the diodes are 1N4004 (these rarely fail) you can buy them from mouser http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/1N4004/?qs=sGAEpiMZZMuQUXCJI7Y4lnwnhMohE%2fNv

Buy them in quantities of 100 and they will only be $0.053 each...sad thing is shipping will cost you a little more than that.

You can also get them from Marco http://www.marcospecialties.com/pinball-parts/1N4004 for $0.19 each. This is good to know if you just want a couple and you are already buying other parts from Marco.

ibjames ... if you find out that this is a MPU related problem, or just want your board tested...I'll repair/test your board for free (only if it has no acid damage) since I have nothing on my bench right now. Just PM me if you want to go this route.

We worked on the game for about six hours last night. The wires in the harness all seem to be fine. Our guess is that it is board related. We pulled the board and it looks okay, no major corrosion, etc. We have no clue how to use a logic probe. If your willing pin_guy we could ship it out with a return label? More than happy to compensate for your time.

The issue James posted before regarding the two banks of three yellow target switches is still present. If you hit all but one of the targets in switch edge tests it registers the target, then the trough up switch registers which is the last opto in the ball trough. Maybe the board is causing this also?

Can I take the cpu board out of my shadow or tz to put in this machine to see if the board is causing these issues?

TZ should have the same MPU as STTNG (A-12742-XXXXX) so yes, you should be able to put the STTNG ROM in it and swap it into the machine. Please keep in mind if there is problem in the playfield that took out the MPU, you could end up with two bad boards.

If you want to test the STTNG MPU, it may be better to put in into a known working machine like your TZ.

The Shadow uses a WPC-S board, so it's not going to be the same part.

Return label will be fine, I'll PM you my information. The parts are very inexpensive and I have them all on hand, I really don't think it will be that hard to fix as long as there is no acid damage.

The alkaline damage to the board, while in the early stages, appears to be fairly extensive and I've recommended replacing the board.