Okay, after a 4.5 year break, I can proudly announce that I'm done being an ignorant middle schooler. Thank you guys for being so patient with 15 y/o me
The "-5v" from having my probes backwards absolutely kills me.
I was getting ready to sell the poor thing as-is on ebay, but started looking through all of the documentation I got with it and decided it was far too interesting and important to get rid of. So I'm back at trying to fix it again.
The current status of the machine is that it displays nothing upon first startup, but a quick flick of the power switch off and on again gets it to display garbage characters (some of which slowly morph over time). I have removed all but one pair of the RAM, and the video is still corrupt. As suggested by Klyball, I swapped the RAM on the video board with the same result. Unfortunately I have no way to tell what RAM chips are good and which are bad; any suggestions on a tester? Thankfully the break key still changes the output. Where do I go from here?
Also, the video board seems to be hurt in other ways. The output starts off strong and clear, but gets more and more dim as it heats up. Or perhaps its a power supply issue?