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From: krowitz@RICHTER.MIT.EDU (David Krowitz)
Newsgroups: comp.sys.apollo
Subject: DN2500 disk cables
Message-ID: <9008091420.AA24320@richter.mit.edu>
Date: 9 Aug 90 14:20:47 GMT
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It's my turn to ask for help ...

We just got a Quantum 170MB internal disk for one of our DN2500's.
Of course, it came with cables for a Macintosh, so I'll have to 
make my own cables for the DN2500. I think I understand how to
make the SCSI cable ... with the ribbon cable laying flat on the
table, one of the 50-pin connectors should be attached so that the 
notches for orienting the connector are up, and the other 50-pin
connector should be attached so that the notches are down. This
gives a cable which attaches the left side of the connector on
the CPU to the left side of the connector on the disk, which is
how the SCSI daisy chaining is done on the Macintosh cable.

From a side view, the Mac SCSI cable looks like this:

    +-------+                      
    |       |
    +-------+.....................................+-------+
                                                  |       |
                                                  +-------+

The power cable is more of a mystery to me, as the Mac power
cable has two different connectors on it, and the drive's
pins on the power cable connector aren't labled. The DN2500's
power cable uses two indentical 4-pin connectors which are
keyed to insure the proper orientation. Two of the possible
configurations are a straight accross or a X-cross. Ie. from
the top view with both connectors oriented with the notches
on top:


    +-------+                                     +-------+
    |   red |+...................................+| red   |
    |       |                                     |       |
    | black |+...................................+| black |
    |       |                                     |       |
    | white |+...................................+| white |
    |       |                                     |       |
    | green |+...................................+| green |
    +-------+                                     +-------+


                           or

    +-------+                                     +-------+
    |   red |+..............\     /**************+| green |
    |       |                \   /                |       |
    | black |+==========\ /----------------------+| white |
    |       |            X     X                  |       |
    | white |+----------/ \======================+| black |
    |       |                /   \                |       |
    | green |+**************/     \..............+| red   |
    +-------+                                     +-------+


If you have a working DN2500 with an internal disk, could
you check your cables and tell me whether I'm on the
right track?



 -- David Krowitz

krowitz@richter.mit.edu   (18.83.0.109)
krowitz%richter.mit.edu@eddie.mit.edu
krowitz%richter.mit.edu@mitvma.bitnet
(in order of decreasing preference)