I think by the time I'm done, I might have a new thread in this forum for fixing every type of Mac...haha.
Last June I bought a non-working Color Classic on eBay. I tried to turn it on and nothing happened. Yes, I had the power switch on the back turned on, and I was pressing the keyboard power button. The Color Classic does not require a PRAM battery to start, so it had nothing to do with the non-present battery.
I looked at the logic board, and sure enough...leaky caps. Luckily, the leakage didn't seem too bad. I removed all the caps and ICs nearby the caps (which was smart, because nearby ICs had some capacitor goo underneath). I cleaned as well as I could with 99% isopropyl alcohol. I also tested all vias nearby capacitors by testing continuity between components on the top and bottom that were connected by the vias.
U7 is the CUDA chip, and the broken via is part of the crystal circuit for the CUDA chip. So basically, the CUDA chip wasn't being clocked, explaining why there was a power on problem.
Finding all the vias was tough. My strategy was to take a picture of the top and bottom of the board, and match up vias by color coding them in an image editor. It ended up working pretty well and made it easier to test everything! The vias on the Color Classic board are a lot smaller than they look in the pictures. In my particular case, here's how I fixed it:
After replacing all the caps with tantalums and applying that patch, I now have a working Color Classic. Woohoo!