When my Data General Eclipse MV9800 system, arrived I was rather excited to find a number of DG SCSI II controllers in the chassis. One of these was presented to the outside world via a DB50 connector. Great I thought until I tried to use it with a standard SCSI DB50 to CN50 cable – it did not work! VIP Mario kindly sent me various pictures from a phone of some pages from the Inferno manual he had on Fiche, specifically the back-plane cabling and it was apparent that DG did not adopt the SCSI standard when presenting this DB50 to the outside world. Perhaps they had a cunning new cabling design that would revolutionise SCSI or maybe they wanted to make sure you bought the DG DB50 to CN50 cable – who knows 🙂
So the challenge was to either convert the DG DG50 presentation by making a new DB50/CN50 cable or convert/make a new back-plane to DB50 cable that would conform to SCSI standards – I opted the the latter.
VIP Mario came up trumps again (Thanks Mario) as he offered to send me a 100pin connector and the crimp pins to allow me to make the internal cable.
To reduce the amount of crimping I opted to use a ribbon cable and a DB50 IDC connector (not cheap!) which just left the back-plain end to sort out. The first job was to test each of the 50 conductors to ensure good conductivity and place each one in its correct position in the back-plane connector – I tied a not in each cable to stop them drifting back out. I could then cut each cable to ensure I kept an orderly (as possible) arrangement of cables entering the connector.
And here we have it my finished cable which presents the SCSI signals to the outside world on the pins they should be presented on!
If you would like to make one yourself the back-plane and DB50 pin outs can be found here: https://www.datageneral.uk/repository/data-general-hardware/005-038601-scsi-ii-controller-6786-6787/
My MV/9800 resotoration pages can be found here: https://www.datageneral.uk/restorations/mv9800-system/