The upside-down capacitor in mid-‘90s Macs, proven and documented by hobbyists
"Am I the first person to discover this?" is a tricky question when it comes to classic Macs, some of the most pored-over devices on the planet. But there's a lot to suggest that user paul.gaastra, on the 68kMLA vintage Mac forum, has been right for more than a decade: One of the capacitors on the Apple mid-'90s Mac LC III was installed backward due to faulty silkscreen printing on the board.
It seems unlikely that Apple will issue a factory recall for the LC III—or the related LC III+, or Performa models 450, 460, 466, or 467 with the same board design. The "pizza box" models, sold from 1993–1996, came with a standard 90-day warranty, and most of them probably ran without issue. It's when people try to fix up these boards and replace the capacitors, in what is generally a good practice (re-capping), that they run into trouble.
The Macintosh LC III, forerunner to a bunch of computers with a single misaligned capacitor. Credit: Akbkuku / Wikimedia CommonsDoug Brown took part in the original 2013 forum discussion, and has seen it pop up elsewhere. Now, having "bought a Performa 450 complete with its original leaky capacitors," he can double-check Apple's board layout 30 years later and detail it all in a blog post (seen originally at the Adafruit blog). He confirms what a bunch of multimeter-wielding types long suspected: Apple put the plus where the minus should be.