On Sun, Apr 24, 2016 at 1:06 PM, Mark G Thomas <[email protected]> wrote:
> Hi, > > So far, the only M8330 prints I have found are extremely fuzzy, so I cannot > make out the IC identifiers or match them up to the equally fuzzy > schematic. > You do know about bitsavers.org, yes? Al has lots of very clear scans of DEC prints. Keep in mind, though, that these are hand drawn prints - sometimes you have to zoom to 150% or 200% to make out particular letters/digits. > By board-inspection I identified the 74S74 "run" flip-flop, and in fact I > can un-stick the RUN state by briefly grounding CLR, but still cannot > DEP or EXAM from the front panel -- it gets stuck back with RUN on if I > hit either DEP or EXAM again. > > The power supply voltages are right-on. I've reseated and repositioned > the boards. The connectors are very clean. Wiggling boards doesn't change > any of the symptoms. Wiggling switches doesn't affect anything. This is > a very clean 8/e. > Check not only your voltages, but your power waveforms. Also, I remember having an issue involving a race condition with the DC OK line, which is not often considered when one is checking power supply voltages. If the +5 rail isn't solid *before* DC OK comes up, this will lock up things. Have fun -- Ian K7PDP -- Ian S. King, MSIS, MSCS, Ph.D. Candidate The Information School <http://ischool.uw.edu> Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical Narrative Through a Design Lens Archivist, Voices From the Rwanda Tribunal <http://tribunalvoices.org> Value Sensitive Design Research Lab <http://vsdesign.org> University of Washington There is an old Vulcan saying: "Only Nixon could go to China."
