ST700 GENERAL HANDBOOK
667/HB/27880/000 Page 81 Issue 8
6.4.5 Replacement of CPU PCB
Ensure that the replacement PCB has the correct firmwares fitted and they are of the
correct variant and issue. Refer to the Works Order Specification for details.
The mounting pillars on the CPU are a nylon clip type and only require the clipping
mechanism to be released to allow the board to be removed. The pillars are retained
on the hinge plate by means of an integral clipping mechanism on the other end.
When the CPU is replaced, make sure that the clipping mechanism of the mounting
pillar is fully engaged.
Warning Care must be exercised when removing or inserting the green connectors
and their cables from the PCB, as strong extraction and insertion forces are required.
Be careful not to over flex the board, which could cause tracks to fracture and the
board to fail.
6.4.6 Replacement of Power/Phase Assembly
The Power/Phase assembly may be removed once the following have been carried
out:
Isolate the Mains to the ST700 at the master switch
Disconnect the 64-way Phase Control ribbon cable from the CPU
Unclip the earth lead from the hinged front plate
Remove the front plate
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holding the CPU (and I/O or OTU) and store carefully
Disconnect the earth wires from the fixing point in the assembly
Disconnect PL6, PL7, PL8 and SK2
Disconnect PL1 and SK1.
Warning Care must be exercised when removing or inserting the green connectors
and their cables from the PCB, as strong extraction and insertion forces are required.
Be careful not to over flex the board, which could cause tracks to fracture and the
board to fail.
Using a 10” Pozidriv No.1 screwdriver, loosen (do not remove) the four screws
holding the Power/Phase assembly to the equipment mounting plate. Lift the
assembly off the mounting plate.
Replace with the new Power/Phase assembly, checking that the part numbers are
the same, i.e. 2 phase, 4 phase or 6 phase unit.
Ensure that all links and fuses are set correctly (i.e. in the same position as the
original unit) as described in section 5.15.
Reconnect PL1, PL6, PL7, PL8, SK1, SK2 and the earth wires.
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The front plate needs to be at 90º when it is fitted or removed. Push the front plate
up and remove from the bottom hinge pin. Pull down to release the front plate from
the top hinge pin.
