Natalie The Nerd has been archiving information needed to reverse engineer classic Nintendo handhelds and is hosting the information on her wiki for free. This information includes scans of the PCB’s, as well as scans with the protective layer removed and the copper visible. Natalie also has schematics and CPU pinouts for a few of them as well. If you’re repairing broken motherboards, or are creating new products for use with these systems, this information will likely be very helpful:
wiki: https://wiki.nataliethenerd.com/
Main Site: https://nataliethenerd.com/
While other projects like the “Strip Club” PCB scanning archive have existed for awhile (and are also extremely helpful), it’s great to have this info in a wiki-style site. Natalie also sells very cool products, like the Poco Plus that’s a drop-in replacement for the Game Boy Color (just transplant a CPU and RAM from the original), which includes modern mods already built-in. I’m a big fan of stuff like this, as there’s tons of totally trashed handhelds out there, that most likely have CPU’s and RAM that can be salvaged. You can use motherboard like that, as well as new cases, buttons, etc to essentially built a modern, “brand new” Game Boy, with only the main proprietary chips required.
Check out the site and wiki for more info.