Just an FYI. I had a 68040 board which after racap and cleaning still did not boot. The behavior was that the board would start the machine, but the LED on the logic board would not light up and the screen would come on with no image. Basically an illuminated black screen. I figured it had something to do with very low level functionality if the diagnostics lights weren't working, but I rarely suspect a CPU. In the end the problem was that the CPU had 2 pins which were physically detached and stuck in the socket. The damage did not look forced actually, and to my eye looks like the package bonding actually failed which is an interesting failure mechanism.
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Brian
That sounds a lot like a thermal stress issue.
Agreed. Never seen it happen on a 68040 though.