Isolating and Repairing Packet-Bus Faults
Issue 1 May 2002
4-107555-233-143
If the packet-bus problem is present when the circuit pack is inserted, but is
resolved when the circuit pack is removed, either the circuit pack or the backplane
pins in that slot caused the problem. If the backplane pins are intact, replace the
circuit pack. Keep in mind that there may be more than one failure cause.
In ‘‘Procedure 2: Removing and Reinserting Port Circuit Packs’’, you may try one
circuit pack at a time, or multiple circuit packs simultaneously. The allowable level
of service disruption should guide this choice. If the entire port network can be
disrupted, trying large groups of circuit packs will save time. If traffic is heavy,
trying one circuit pack at a time is slow but will minimize outages.
If the TN771D’s stand-alone mode does not indicate packet-bus faults, perform
Procedure 2 for only the port circuit packs (purple slots) listed in Table 4-8 on
page 4-106 in Procedure 1. In this case, you need not check for problems with
the backplane pins. It is sufficient to determine whether the problem is resolved
by removing circuit packs.
If you decide to remove multiple circuit packs, consider working with an entire
carrier at a time to more quickly and reliably determine which circuit packs are not
the source of trouble. Any circuit packs (packet or non-packet) that have been
recently inserted should be checked first. Packet circuit packs should be checked
before non-packet circuit packs.
1. Remove one or several circuit packs.
2. Determine whether the packet-bus fault is still present. If not, go to step 4.
3. If the packet-bus fault is still present:
a. Determine whether the backplane pins in the removed circuit pack’s
slot are bent using the output from the Maintenance/Test circuit
pack’s stand-alone mode and the backplane illustrations that appear
earlier in this discussion.
b. If the backplane pins are bent:
Power down the carrier (see ‘‘Replacing a BIU or Rectifier’’ on page
4-9), straighten or replace the pins, reinsert the circuit pack and
restore power. Repeat step 2 for the same circuit pack.
c. If the backplane pins are not bent:
Reinsert the circuit pack(s), and repeat this procedure for the next
set of circuit packs.
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