Quoted from mjthompson:
I've had my WH2O torn down for far too long (over a year). It's a re-import from Denmark that I've had for 15 years. I finally decided to do a thorough shop job (not a restore) to get rid of the smoke smell (yes still). I took the playfield and all the boards out. I'm in the process of putting the boards back in the head. Is it best to test the boards first without connecting any harnesses/ribbon cables and then slowly add everything back in? I have switch & lamp matrix testers that I got last black friday so it seems like it would be best to test that way first. I searched the forums but didn't find anything that described a systematic approach like this.
What I like to do is hook everything up except the playfield. Most issues I've had have been playfield related. There are two harnesses from the cabinet, one is power from the transformer (you'll need that for anything to work) and the other is to all the cabinet components (you'll need that for the coin door switches to work for testing).
You'll need the speaker panel with display hooked up.
You'll need the ribbon cables hooked up as they send signals between the boards.
Lastly, there's a smaller cable that connects power between all the boards. You'll need that too.