online I am not aware of any; I would be glad to be corrected. Unlike the early gneration of UNIBUS CPU's, these generally weren't intended for internal fault analysis and repair - module swapping and replacement was the intended approach. The LSI-11 manual (EK-LSI11-TM-003) has a tiny bit of detail on how the CPU board works (pp. 4-3 - 4-13), it's probably worth reading that before diving into the CPU board internals. Things I'd check to start with - all the power voltages, and then the clocks. If those are all OK... BTW, for any serious fault analysis on these things, you'll need a 'scope/logic analyzer. either When you say 'does not respond', what's the symptom? Is the console ODT not running (which could have any number of causes)? The whole system has to be more or less running for ODT to work. I'd start elsewhere - e.g. does your mounting box have the 'run' light? (It's driven by an output of the CPU card.) Does that display any activity? Time to look at e.g. BSYNC, etc to see if the CPU is trying to read/write the console registers. Noel