While not on a 780 back plane, about 50 years ago, I was basically in
charge of some 26 PDP16M computers. Periodically, one of the chips would
be found with the top blown off. At some point, I pulled the computer
and examined the backplane filled with wirewrap wires.
The solution turned out to be fairly simple... a -15V bus was about
.001" near one of the wirewrap posts. A slight moving of that bus away
from the wirewrap post solved that problem. I have to assume it was a
temperature related problem since increasing that spacing solved the
problem.
Unrelated to the computer problem, another source of angst was
intermittently one of those computers would crash. That one took
probably a year to find... one of the interface M series pullup cards
had a pulldown card installed in its place.
I should mention all the above took place on a newly install system.
Marvin
