Building An External SCSI Connector

Pin connections for external SCSI-2 half-pitch connector:

  NOTE: Connector is VIEWED     |\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  FROM THE BACK, or inside      |  1                       49  |
  of the computer.  All odd-    |  --------------------------  |
  numbered wires go to the      |  \                        /  |
  top of the connector, and     |   ------------------------   |
  all even-numbered wires go    |  2                       50  |
  to the bottom.                |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\|

Procedure: obtain the connector from Redmond Cable. Split the 50-pin SCSI ribbon cable connectors back a couple of inches. Start with pin 1, lay it in the crimp-on pins at the upper left of the connector (again, viewed from the back of the connector). By placing the two sides of a small pair of needle-nose pliers on the wire on either side of the crimp pins, you can gently force the wire down into the V-shaped gap between them. Locate wire #2, then use the same procedure to connect it to the other side of the connector. Repeat for all 50 wires, then clip the plastic retaining clips onto the connector and give it a final squeeze to make sure all wires are making contact.

You can cut a hole in the A4000's Expansion port cover on the back of the machine to hold this new connector (a "nibbling" tool works well for this).

Don't forget proper SCSI termination: the devices at both ends of the chain should be terminated. If the internal SCSI cable leads from the controller to an internal drive, and then to this connector, the internal drive must be unterminated for this port to be functional. When used in this configuration, the external device plugged into this port needs to be terminated. Half-pitch terminators are available from Dalco; using one of these would allow you to operate the A4000 with or without an external SCSI device without having to open up the computer to change termination.