2.4 REMOVING THE FRONT PANEL
Warning:
Before removing the front panel to replace a PCB, you must first remove the
auxiliary power supply and wait 5 seconds for the internal capacitors to
discharge. You should also isolate voltage and current transformer connections
and trip circuit.
Caution:
Before removing the front panel, you should be familiar with the contents of the
Safety Information section of this guide or the Safety Guide SFTY/4LM, as well
as the ratings on the equipment’s rating label.
To remove the front panel:
1.
Open the top and bottom access covers. You must open the hinged access covers by more than 90°
before they can be removed.
2. If fitted, remove the transparent secondary front cover.
3. Apply outward pressure to the middle of the access covers to bow them and disengage the hinge lug,
so the access cover can be removed. The screws that fasten the front panel to the case are now
accessible.
4. Undo and remove the screws. The 40TE case has four cross-head screws fastening the front panel to
the case, one in each corner, in recessed holes. The 60TE/80TE cases have an additional two
screws, one midway along each of the top and bottom edges of the front plate.
Do not remove the screws with the larger diameter heads which are accessible when the
access covers are fitted and open. These screws hold the relay in its mounting (panel or
cubicle).
5. When the screws have been removed, pull the complete front panel forward to separate it from the
metal case. The front panel is connected to the rest of the circuitry by a 64-way ribbon cable.
The internal circuitry is now exposed and is not protected against electrostatic discharge
and dust ingress. Therefore ESD precautions and clean working conditions must be
maintained at all times.
6. The ribbon cable is fastened to the front panel using an IDC connector; a socket on the cable and a
plug with locking latches on the front panel. Gently push the two locking latches outwards which eject
the connector socket slightly. Remove the socket from the plug to disconnect the front panel.
2.5 REPLACING PCBS
1. To replace any of the PCBs, first remove the front panel.
2.
Once the front panel has been removed, the PCBs are accessible. The numbers above the case
outline identify the guide slot reference for each printed circuit board. Each printed circuit board has a
label stating the corresponding guide slot number to ensure correct relocation after removal. To serve
as a reminder of the slot numbering there is a label on the rear of the front panel metallic screen.
3. Remove the 64-way ribbon cable from the PCB that needs replacing
4. Remove the PCB in accordance with the board-specific instructions detailed later in this section.
Note:
To ensure compatibility, always replace a faulty PCB with one of an identical part number.
MiCOM P747 Chapter 15 - Maintenance and Troubleshooting
P747-TM-EN-1 373
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