http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Game_resets
Pinwiki has a good reset section.
And I'm sorry to say you likely screwed it up worse. Easy to do board damage when you replace things, especially the big capacitors. Easy to lose through board continuity or damage solder pads and traces.
And your problem may not have even been on the board.
If it were me, I'd send the board to an expert and get that fixed, and then figure if you have anything else going on with the game.
LTG : )