AC Repair and Adjustment Procedures
FRP 9: Bottom Module Rail Replacement
HMM-168-A
Cray Research/Silicon Graphics Proprietary
61
8.
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 lower PEM rails come with new torus ribbon cables and
new GigaRing cables. Replacement lower clock rails come with a new
clock-to-WACS cable (P/N 57263800).
9.
Disconnect the cables that you will remove along with the rail:
a. Disconnect the associated logic (torus) connections in the wiremat.
(Refer to
FRP 10
.)
b. Disconnect the associated GigaRing connections from the I/O
bulkhead. (PEM rails only.) Use a 1/4-in. socket wrench to remove the
two jackpost screws that secure the GigaRing connector to the I/O
bulkhead.
c. If you are removing the bottom clock rail, disconnect the clock WACS
connection at the I/O bulkhead. Two small flathead screws secure the
WACS cable to the bulkhead.
d. If you are removing the bottom clock rail, record and disconnect the
associated clock wires using a leadless 0.3-mm mechanical pencil
(refer to
FRP 12
).
NOTE:
Removing clock wires is an intricate process; refer to
FRP 12
for details.
10. Use the hex wrench to loosen (but not remove) the shoulder screw from
the power supply end of the rail. Be careful of the power supply
connectors and the digital ground plane.
11. Remove the shoulder screw from the other end of the rail.
CAUTION
When you remove a bottom rail,
ensure that it does not drop through
the slot when you attempt to remove it.