Replacement Of Manual Panel Pcb - Siemens ST750 General Handbook

ST750 G H
ENERAL ANDBOOK
• 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 5.13.
Reconnect PL1, PL6, PL7, PL8, SK1, SK2 and the earth wires.
Replace the hinged front plate holding the CPU PCB and, if fitted, the I/O or OTU
PCB.
Replace all the cables to the CPU. Clip the earth lead to the front plate.
Restore power to the ST750.
Note: The new Power/Phase assembly is supplied with a chassis door fitted. It is
not necessary to replace the door when the Phase Drive PCB has failed. The old
Power/Phase assembly should be returned to Siemens Poole with the replacement
door.

7.4.7 Replacement of Manual Panel PCB

First unplug the cable connecting the manual panel to the CPU PCB.
The manual panel is held to the main Cabinet Assembly by a number of screws that
need to be removed. After removing these screws the panel may remain held in
place by the sealing strip. Ease the panel away from the housing, gradually working
from one corner, taking care not to scratch or otherwise damage it.
The replacement panel should be mounted with a new sealing strip to prevent water
ingress. After fitting, reconnect the cable to the CPU PCB.
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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.
667/HB/33750/000 Page 103 Issue 6