Avaya MCC1 Maintenance Procedures page 265

indicated in this case because the TN771 is not defective. Refer to
maintenance in Maintenance Alarms Reference (555-245-102), and ensure that a -5 volt power supply is
available.
Troubleshooting procedures
As we discussed earlier in this chapter, Packet Bus faults are usually caused by a defective circuit pack
connected to the backplane, by bent pins on the backplane, or by defective cables/terminators that make
up the Packet Bus. The first two faults cause shorts, while the third fault causes either shorts or opens.
There are four procedures for correcting Packet Bus faults. The number of procedures that are to be used
to correct faults depends upon a number of factors relevant to system performance and to the content of
the procedures themselves. For example, if the Maintenance/Test Packet Bus port is activated, and if
there is an indication of open leads on the Packet Bus (either via the
#572 failure), go directly to Procedure 4. The reason for this is that Procedures 1 through 3 try to locate
faulty circuit packs or bent pins behind circuit packs. Since these types of failures can never cause open
faults, Procedures 1 through 3 need not be implemented in this case. However, if there are both shorts and
opens, execute Procedure 4, then return to Procedure 1 if there are still shorts after the open lead
problems are resolved.
CAUTION:
Since Packet Bus fault isolation procedures involve removing circuit packs and possibly
disconnecting entire carriers, these procedure have a profound effect on service.
Therefore, if possible, implement these procedures after hours or during hours of
minimum system use.
Each of these procedures contains one or more steps that require a determination as to whether the Packet
Bus problem has been resolved. Accordingly, several condition checks must be performed. We can
present each such check in the form of a question, as follows:
• Did the Maintenance/Test circuit pack standalone mode initially indicate the existence of faulty
leads, and are these leads no longer indicated?
• Have all alarms against the Packet Bus and Packet circuit packs been resolved?
NOTE:
If all alarms are resolved, issue the
switch back into the service state by resolving any BRI problems that exist.
• Are all ISDN-BRI stations and data modules as well as any relevant ASAI adjuncts in service?
If one of these conditions is not yet met, the others need not be checked. The following sections discuss
the four procedures for correcting Packet Bus faults.
Procedure 1
Procedure 1 determines if any circuit packs that use the Packet Bus have faults.
Maintenance Procedures
December 2003
Packet and serial bus maintenance
S8100 packet bus fault isolation and repair
CARR-POW (Carrier Power Supply)
status system
clear pkt command. This command attempts to put the
command or via Test
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