I've always been a big Stern video game fan, still own a Minefield upright and picked up another Minefield board a month ago. The board was sold as untested, was hopeful it would work, but it came up with video issues as shown below.
The board did appear to play, just hadscrambled video that was scrolling a bit as well. Minefield boards are basically modified Scramble boards (and probably other classic Stern games). Dug out my Scramble schematics and after 10 minutes realized that my VSYNC signal was missing at 8L and 9D, but present at 8L. Quick visual inspection showed a damaged trace that I jumpered. The board's video looked much better but was still rolling and not locking in. Tried it on another monitor and it did the same thing. Checked my work and there was also a second trace that the gouge took out. Fixed this one as well and the board fired up perfectly as you can see.
One of the golden rules of board repair is always do a visual inspection prior to starting work, I did do one, but apparently not well enough as I didn't catch the broken trace until some troubleshooting work.