My Quadra 650, which was severely battery bombed but amazingly still functions after quite a bit of cleaning, has two 512 KB VRAM SIMMs from Garrett's Workshop installed, but the OS isn't offering me thousands of colors at 832x624; it only offers me 256 colors. This points to a problem with either the sockets themselves or the traces around them. Following such tiny traces to check continuity is problematic at best since I have only my eyes and my reading glasses to work with, and I don't know where each trace is headed. If someone has the schematics for the board, could those please be shared? It would make checking continuity as simple as checking each end of the path.
It's also possible that the SIMMs themselves have a problem, but I don't have a way to check right now because my Performa 476 decided to die on me. I suspect the PSU, but the caps I ordered based on RECAP-A-MAC turned out to not be for my model of PSU. I found the correct guide on Mac84.net, so I can get to that when I can afford to get more caps.
It's also possible that the SIMMs themselves have a problem, but I don't have a way to check right now because my Performa 476 decided to die on me. I suspect the PSU, but the caps I ordered based on RECAP-A-MAC turned out to not be for my model of PSU. I found the correct guide on Mac84.net, so I can get to that when I can afford to get more caps.