Ref: 17300003
Title: Making Diagnostics Loopback Plugs for the 3Server
date: 5/3/91

Copyright 3Com Corporation, 1991.  All rights reserved.

Loopback Plugs

Server diagnostics tests require Ethernet, serial, and LocalTalk
loopback plugs.  If loopback plugs are not available, you can make
them as described in the following sections.  For a more complete
discussion of these diagnostics tests, see the 3Server Technical Reference
and Service Manual for the 3Server/500 or the 3Server386 (3S/400) server.


BNC Loopback Plug

Make a BNC loopback plug by attaching a 50-ohm terminator to each end of a
thin Ethernet T-connector.  Install the loopback plug on the BNC connector
on the server's rear panel.


COM Port Loopback Plug

The IBM loopback plug (P/N 8529208) for testing serial ports has
a different pinout configuration than 3Com's loopback plug.  The
IBM loopback plug will not work in testing the 3Server serial
ports.  Connect the pins in a DB25 connector as shown.

          2    --   3
      4,5,8    --   22
          6    --   20
         17    --   24


Parallel Port Loopback

Attach a parallel printer to the parallel port.


LocalTalk Loopback Plug

Make a loopback plug by connecting pin 6 to pin 8 and pin 3 to pin 5 on
a LocalTalk plug.  Install the plug on the LocalTalk connector on the
server's back panel.

