Looking for DEC M7264-CB Troubleshooting Documentation

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu May 9 12:41:46 CDT 2019

    > From: Mister PDP

    > I was wondering if any in depth troubleshooting material existed 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.

    > When powered on, the CPU does not respond to the Run/Halt switch either
    > on the front panel or via the console.

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.


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