Sun Archive SCSI-Loopback-Connector:

A terminator is not the same thing as a loopback connector. The loopback connector is used only for tests. It connects various parts of the SCSI interface to other parts so you can be sure that everything works. The loopback connector for the DD-50 used by the 3/60 is constructed as follows:

Connect:

Pin# to Pin#
38 ---> 16
36 ---> 14
44 ---> 12
32 ---> 10
48 ---> 8
42 ---> 6
46 ---> 4
50 ---> 2
40 ---> 18

It is not clear why they listed them in the order that they did. However, you need to either get one of these, or make one. Get a DD-50 male shell, 18 crimp-on pins, and 9 4" lengths of wire. (Some could be shorter, but if they are 4" all should be long enough.) Shove the pins into the appropriate holes on the connector shell, and you have your loopback connector.