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MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)
37
MR850 Model Number Supply Voltage Fuse Type Part Number
MR850Jxx 115 V~ F1: 1 A 250 V FastBlow
F2: 4 A 125 V FastBlow
F3: 3 A 250 V FastBlow
F4: 3 A 250 V FastBlow
999 830 001
999 830 017
999 830 012
999 830 012
MR850Gxx 100 V~ F1: 1 A 250 V FastBlow
F2: 4 A 125 V FastBlow
F3: 3 A 250 V FastBlow
F4: 3 A 250 V FastBlow
999 830 001
999 830 017
999 830 012
999 830 012
WARNING:
Be sure to replace the fuse with the correct rating and type. Do not under any
circumstances replace F2 with anything other than a fast blow fuse of the type and rating
specified, as serious injury could result.
3. Replace fuse.
4. Close the case (section 7.2.8).
7.2.3 Replacement of Printed Circuit Boards (PCBs)
1. Open the case (section 7.2.1).
2. Disconnect all harnesses attached to the power PCB. Disconnect the mains and protective
earth wires by unscrewing the terminal blocks, and cutting the cable ties (Figure 7.4).
3. Remove PCBs, and using an appropriate tool, remove the ROM from the 32-pin socket on
the control PCB. Store the ROM in an antistatic bag or box.
4. Unpack replacement PCBs, install the ROM from the previous PCB.
5. Replace the mains fuses (F3, F4) with the correct type, and attach mains and protective
earth wires, using the cable ties provided (Figure 7.4).
6. NOTE: If revision A PCBs are being replaced with revision C PCBs or later, (look for
identification on the control board), then the wiring of the heater plate thermal cutout (and
thermistor) will need to be changed. Un-clip the four pins from the connector by using a
small flat bladed screwdriver. Re-wire the connector so the thermistor wires (white) are
located on the inner two pins, and the thermal cutout wires (black) are located on the two
outer pins.
7. Connect harnesses from the transformer and heater plate to the power PCB.
8. Close the case (section 7.2.8).
9. Update the EEPROM software version (step 5, section 7.2.6).
10. Check that the humidifier powers up normally, and complete a full performance test
(section 8).