Further PDP-11/05 debugging -- core memory faults

I think the H214 is 8K x 16, and the H215 is the 8K x 18. I thought about rerouting a few times, but never attempted it.

On Sat, Sep 27, 2014 at 11:59 PM, Josh Dersch <derschjo at gmail.com> wrote: > On 9/27/2014 2:11 PM, Tony Duell wrote: > >> Further investigation reveals that the connection between FD1 on the >>> card edge connector (the XS05 signal) and pin 7 of the 2501 at E22 is >>> broken. This, I believe, is a matrix wire (or "magnet wire" from the >>> engineering drawings) meaning that I've got a broken wire somewhere in >>> the core mat. >>> >> I would just trace the tracks, both visually an with an ohmmeter, from >> the edge conector pin to the core mat and from the core mat to the diode >> array. Just in case. >> > I'll double check things. My inspection is not made any easier by the > amount of dust covering this thing. I dare not attempt to clean it up, but > it makes finding faults visually pretty difficult. > > >> Incidneatlly, no matter what it says on the cover over the core mat, you >> can take it off quite easily without damage. Just don't drop it on the >> corse. >> >> If it is the core address wire in the mat, you may have big problems. >> Some of these mats had the cores cast onto the array of wires, no >> pre-made cores that were threaded with the wires. In which case, >> replacing the wire might be impossible. >> >> My first throught was 'have a go anyway. If you wreck the board, well, it >> doesn't work now'. And then I thoguth that no, you should treat it with >> care. Even if you don't have the skill to fix it now, you might do so i >> nthe future. Or somebody else might have a go. In any case, you don't >> want ot make thigns worse. >> > I do have a semi-crazy idea: The H214 I have is 8Kx18 bits (i.e. > parity). If I were to disable parity on the control boards and reroute one > of the parity-related lines for this damaged section, maybe I could get a > complete 8Kx16? > > I'll have to do a bit more research... > > - Josh > > > > >> -tony >> >> >>