I dumped a lot ( A LOT! ) of money into a Gottlieb Volcano.
Found a wonderful guy who sold me a practically brand spanking new inner backglass he had hanging in his gameroom for 20 years. Bought a set of the PBR repro plastics. Did a complete playfield restoration with clearcoat. Cleaned all under playfield assemblies, polished every nut bolt and screw. Replacement drop targets, flipper rebuild, new rubbers, the whole works. Rebuilt power supply, did all ground mods, and pull up resistor mods. Added caps to solenoids to prevent sparking/arcing, and even added in-line fuses to the coils that aren't CPU controlled (slings, kickers). Only thing I didn't touch was the cabinet as I really don't have the tools or knowledge to do cabinet restoration.
Sold it to a System 80 collector from MN. Real nice guy. He seemed to like it
https://picasaweb.google.com/110151734903422637614/VolcanoBefore
https://picasaweb.google.com/110151734903422637614/VolcanoTouchedUpAndClearcoated
https://picasaweb.google.com/110151734903422637614/VolcanoAfter
https://picasaweb.google.com/110151734903422637614/VolcanoBackglass