No matter what certain books and websites say, IMHO you should always have some kind of current limiting resistor when discharging a CRT. Otherwise, as you unfortunately discovered, the can be voltages induced in the strangest placed that will blow semiconductors. I normally use my EHT probe, it's got a internal resistance of 800M, and will discharge a CRT in a couple of seconds. The corerect point to discrhage to in just about all machines/monitors is the outer aquadag coutaing. After all, what you're discharging is the capacitor formed by the inner and outer aquadag coatings on th CRT flare. In quite a number of machines, that outer coating is connected to wire on the same connector as the CRT base wires. which means it takes a somewhat circuitous route to chassis. Hence, alas, your problems What's odd is that it's running at all.. My first thorught is you've lost some DTAck/ generation, and the processor is extending every bus cycle until it times out. That would certainly slow things down a lot. I've never been inside a Mac 512, but I've worked on a Mac+. The problem is thst most of the logic is in HAL chips (Hard Array Logic -- mask programmed gate arrays with the saem architecture as a PAL). And AFAIK there's no way to read out the 'fuse map' from a HAL (certainly I've never managed it). So I don't have the logic equations, which makes troubleshooting, and indeed repair, a little hard. I thinkl I would start wih the one chip you certainly know, the 68000. Look to see if the bus cycles (AS/ width, etc) look reasonable. -tony