
AC Repair and Adjustment Procedures
FRP 8: Top Module Rail Replacement
HMM-168-A
Cray Research/Silicon Graphics Proprietary
55
10. Study the replacement rail assembly to determine which cables and wires
you will replace along with the rail. Refer to the defective rail and record
the connections that these wires make.
Replacement upper PEM rails come with new torus ribbon cables, a new
PEM-to-WACS cable (P/N 15214200), and a new PEM-to-scan pigtail
(P/N 15214300).
11. Compare the replacement rail assembly to the defective rail to determine
which wires (clock wires only in almost all cases) you will remove from
the defective rail before you remove the rail from the cabinet. Record the
locations where these wires connect to the rail connectors.
Replacement PEM rails do not come with attached clock wires. In
, you will disconnect the existing clock wires from the defective
rail. Later you will connect these clock wires to the new rail.
12. Carefully disconnect the associated logic (torus) wiremat connections that
you must remove along with the rail. (Refer to
FRP 10
.)
13. Disconnect the associated boundary scan connections in the wiremat. (In
most cases, the only boundary scan connections to the rail take place via
the PEM-to-scan pigtail [P/N 15214300], which contains 5 pluggable
connections in the wiremat.)
NOTE:
The scan master PEM, in slot 1 of cabinet 0, also contains
direct connections that you must remove as described in
FRP 13
.
14. Disconnect the WACS connection at the control interconnect bulkhead:
a. Locate the WACS harness connection above the module slot where
you are removing the rail.
b. Use a small flatblade screwdriver to remove the two screws that secure
the WACS harness connector, then remove the connector.
c. Use a 5-mm socket wrench to remove the two screws that secure the
PEM-to-WACS connector to the top of the module exhaust plenum.
Then lower the PEM-to-WACS cable into the wiremat.
15. Carefully disconnect the clock wires from the defective rail. Removing
clock wires is an intricate process; refer to
FRP 12
for details.
16. Prepare the wires and cables, which attach to the defective rail, for
removal with the rail: