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Ref. 185040646 MR730/720/700/480 Technical Manual ¯ Revision F ¯ Issued March 2001
If you are fitting a Revision H or later power PCB to a Humidifier that has a revision F or earlier control PCB , you
will have to ensure correct phase polarity on the transformer secondary wires. To check for correct polarity, turn the
humidifier on, if the humidifier displays F-2, then the polarity of one of the transformer secondaries needs to be changed.
This is accomplished as follows:
i. Unplug the power supply and then unplug the transformer secondary connector (Connector J9) from the power
PCB.
ii. Then carefully remove the two yellow wires from the connector housing by depressing the locking tabs on the
back of the connector terminals and pulling the wires out of the housing.
iii. Insert the yellow wires in to the connector housing in reverse order to what they were before. See below.
NEW WIRING AFTER
POLARITY SWAPPED
EXISTING WIRING
YELLOW
YELLOW
WHITE
WHITE
YELLOW
YELLOW
WHITE
WHITE
SECONDARY
SECONDARY
J9
J9
Replacing revision F or earlier power PCB MR480
If the existing power PCB is Rev. F or earlier, there will be an earth wire from the secondary harness of the transformer to
the chassis. Unclip this wire from the transformer connector and unscrew it from the chassis. The Rev. J replacement
power PCB will have an earth wire attached to the PCB. Fit the end of this earth wire to the earth stud on the chassis.
7.3.2 MR480 TRANSFORMERS
For MR480’s , the transformer secondary wiring changed when Rev. J PCB started. When replacing the transformer,
follow the instructions supplied in the transformer replacement kits to ensure compatability.
7.3.3 SOFTWARE COMPATABILITY
Software versions 1.0 and 2.0 can be upgraded to version 3.0 in their existing PCBs.
Software version 1.0 should be replaced with version 3.0 if the PCB’s are upgraded. Software versions 2.0 and 3.0 are
compatable with all PCB revisions.
7.4 HEATERPLATE
To reset the 118 °C over temperature cutout, separate the case front from the case body, then push the reset button
(through a small hole under the heaterplate in the front panel case assembly).
To replace the heaterplate:
1 Separate the case front from the humidifier body.
2 Unclip the Power PCB from the case body (see § 7.2.2 above).
3 Unplug the heaterplate wires from the Power PCB (connectors J3 and J7).
4 Unscrew the earth screw on the chassis for the heaterplate earth wire.
5 Unplug the ribbon cables from the Power PCB to the Control PCB (connectors J1 and J2). The front case
assembly is now separate from the case body.
6 Detach the heaterplate from the case front by unscrewing the three screws which secure it to the case front.
7 Assembly is the reverse of the above procedure.