Repair Procedure 10 - NCR PC4i Service Manual

LEVEL 1 DIAGNOSTICS ERROR RETURNS
Figure 5-26

Repair Procedure 10

Before starting to troubleshoot the communications
channel it
configuration switches may be checked for the proper
setting. It is also necessary to install a wrap plug
or Turnaround Test Plug (Part No. 017-0044311) for
the RS-232 port. If you do not have such a Test Plug
construct one using an RS-232 female connector with
the pins jumpered as in Figure 10-27. If you have not
already done so, refer to the "System Configuration"
section of this chapter. Most of the bit sensitive
codes that are specified in the error message refer
to the failure of the 8250 communications IC or one
of the associated line drivers. This test can be used
to determine a peripheral device (modem, printer,
etc.) connected
defective. Figure 5-25 shows the location of hardware
used by the serial communications port. To test the
data bus to the 8250 serial communications IC a
printer can be attached to the computer's printer
5-40
Serial Communications Status (2 of 2)
is r e c o m m e n d e d
to the serial
that the
(RSA-232) port is
sy s t e m