I did something similar with an old Gottlieb (those power boards and transformers really are in a bad spot). Was soldering with the game plugged in, so when I let the solder roll drop after doing the repair - zizzle!!  Learned to unplug them when working after that!

If we get enough members willing to share their less than switched on moments, we might set up a "What not to do" Section.......could be just as useful as the helpful tips section.