Mine did that to me on Saturday! I think I just need to redo the CPU socket for mine (it was a known thing with it when I got it).
Nice write up
Always awesome to see people going deeper than just "Replace logic board"
I've started stocking up on 74,74S and 74LS parts recently - cheapest place I found was http://www.futurlec.com/IC74LS00Series.shtml
- not sure if anyone knows of better sources. Doesn't look like my order will be here until Jan 2016 though.