UPGRADING REPAIRING PCs

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Building a Parallel Loopback Plug
Several loopback plugs are used for parallel ports because of the different
testing procedures performed by the various diagnostic programs.
If you have the correct pinouts, you can build your own, or
you can purchase them directly from the diagnostic software company,
either with the software or separately.
Most use the IBM style loopback, but some use the style that originated
in the Norton Utilities diagnostics. Check with your diagnostic
software vendor to see which of these loopback designs is the correct one
for your system, or if a different design is needed.
The following wiring is necessary to construct your own loopback
or wrap plugs to test a parallel port:
• IBM 25-Pin Parallel (Male DB25P) Loopback Connector
(Wrap Plug). Connect the following pins:
1 to 13
2 to 15
10 to 16
11 to 17
• Norton Utilities 25-Pin Parallel (Male DB25P) Loopback
Connector (Wrap Plug). Connect the following pins:
2 to 15
3 to 13
4 to 12
5 to 10
6 to 11
Chapter 7—Parallel Ports, Printers, Scanners, and Drives
Troubleshooting Parallel Ports
Table 7.3 Resolving Parallel Port Problems
Symptoms Cause(s) Solution
Device on port not Wrong parallel- Check device manual; probably
recognized; can’t port setting need to change port to EPP,
configure printer;
printer won’t print
ECP, or EPP/ECP mode.
Wrong cable If you’re using EPP or ECP, you must use
an IEEE-1284 cable.