The best thing about old computers is they're so damn simple, and there are a ton of projects out there to enhance them - for $50 you can get a BlueSCSI which gives you hard drive/optical/network emulation on many machines.
Also, new tools are way more capable and cheap - all you need to fix an old computer with a sub-50mhz bus clock is a multimeter/scope, soldering iron, and other bits, which can easily be purchased new for $200.
Also, new tools are way more capable and cheap - all you need to fix an old computer with a sub-50mhz bus clock is a multimeter/scope, soldering iron, and other bits, which can easily be purchased new for $200.