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Ref. 185040646 MR730/720/700/480 Technical Manual ¯ Revision F ¯ Issued March 2001
7.0 SERVICING INFORMATION _____________________________________
7.1 INTRODUCTION
This section provides information for servicing the MR730/720/700/480 Humidifier. The electronic circuitry is contained
on two separate circuit boards, the power board and control board.
Please note the following:
• Follow ESD precautions when handling circuit boards.
• After replacing or modifying a circuit board, go through the calibration and performance tests outlined in § 5
and 6.
• After any repair involving opening of the humidifier, go through the electrical safety tests outlined in Appendix
B2.
• When replacing any screws, refer to torque settings in § 7.6.
7.2 PRINTED CIRCUIT BOARD REMOVAL
7.2.1 CONTROL PCB
The front panel and heaterplate assembly is separated from the humidifier body by removing the 4 fixing screws from the
rear of the humidifier body. The front panel assembly can now be moved aside and the two ribbon cable connectors (J1
and J2) disconnected from the rear of the control board. If the front panel is now positioned face down the three plastic
retaining latches protruding through the board can be moved in the appropriate direction to release the board. This is
facilitated if a slight upward finger pressure is maintained on either edge of the board, when the latches release, the
board will pop up leaving the push on control knobs behind in the front panel.
7.2.2 POWER PCB
Separate the case front from the humidifier body and disconnect the two ribbon cable connectors joining the Power PCB
and Control PCB (J1 and J2). Cut the cable tie holding the heaterplate and chassis wires together.
The power board and heat sink assembly can now be removed by flexing the case sides away from the top edge of the
board and moving the board forward slightly to disengage from the case. The board should now be lifted slightly to
clear the lower retaining guides and moved further forward to gain access to the various wiring harness connectors
which can now be detached. Before removing the PCB, unscrew the mains cord connections and cut the cable tie
holding the mains cord in place.
7.3 COMPATABILITY
7.3.1 HARDWARE COMPATABILITY
• If a revision D or earlier power or control PCB needs to be replaced, then both PCBs need to be upgraded together
to ensure correct performance. Revision F and later PCBs can be replaced individually.
• To upgrade both PCBs and the software use a PCB service upgrade kit. The part numbers to order are as follows:
Model Part number Model Part number
MR480 043040791 MR720 043040793
MR700 043040792 MR730 043040794
• For humidifiers with Rev F or later PCBs, you will only be required to purchase individual boards for repairs (as detailed in sect. 8.9).
• If a revision H or later power PCB needs replacing, the replacement power PCB must also be revision H or later.
Replacing revision F or earlier power PCB MR700/720/730