P74x/EN MT/N
1, P742, P743
(MT) 11-
Before fitting the replacement module check that the number on the round label adjacent to
the front edge of the PCB matches the slot number into which it will be fitted. If the slot
number is missing or incorrect write the correct slot number on the label.
The replacement module can be slotted in using the reverse procedure, ensuring that it is
pushed fully back on to the rear terminal blocks. To help confirm that the module has been
inserted fully there is a V-shaped cut-out in the bottom plate of the case that should be fully
visible. Re-fit the securing screws.
Note: The transformer and input boards within the module are calibrated
together with the calibration data being stored on the input board.
Therefore, it is recommended that the complete module is replaced to
avoid on-site recalibration having to be performed.
Refit the front panel using the reverse procedure to that given in section. After refitting and
closing the access covers on size 60TE/80TE cases, press at the location of the
hinge-assistance T-pieces so that they click back into the front panel moulding.
Once the relay has been reassembled after repair, it should be recommissioned in
accordance with the instructions in sections 1 to 8 inclusive of the commissioning and
maintenance section P74x/EN CM.
1.3.2.4 Replacement of the power supply board
The power supply board is fastened to a relay board to form the power supply module and is
located on the extreme left-hand side of all differential busbar relays.
Pull the power supply module forward, away from the rear terminal blocks and out of the
case. A reasonable amount of force will be required to achieve this due to the friction
between the contacts of the two medium duty terminal blocks.
The two boards are held together with push-fit nylon pillars and can be separated by pulling
them apart. Care should be taken when separating the boards to avoid damaging the inter-
board connectors located near the lower edge of the PCBs towards the front of the power
supply module.
The power supply board is the one with two large electrolytic capacitors on it that protrude
through the other board that forms the power supply module. To help identify that the correct
board has been removed, Figure 9 illustrates the layout of the power supply board for all
voltage ratings.
Before re-assembling the module with a replacement PCB check that the number on the
round label adjacent to the front edge of the PCB matches the slot number into which it will
be fitted. If the slot number is missing or incorrect write the correct slot number on the label.
Re-assemble the module with a replacement PCB ensuring the inter-board connectors are
firmly pushed together and the four push-fit nylon pillars are securely located in their
respective holes in each PCB.
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