Fisher & Paykel MR730, MR720, MR480, MR700 technical manual Fault Location

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7.4.1HEATERPLATES WITH SCREW-IN STANDOFFS

For products after S/N:9773XXX19731, the heaterplate standoffs were changed to shoulder bolts that screwed directly into the heaterplate.

When fitting these heaterplates,‘click’ the heaterplate springs into the recesses on the heaterplate (by rotating them while pushing down), then align the springs with the holes in the case front and screw in the self tapping standoffs into the heaterplate.

7.5FAULT LOCATION

If neither the digital display nor any of the front panel LED’s are on and no power appears to be reaching the transformer primary, check that the mechanical overheat protector on the heaterplate has not cut out. This may be checked by depressing the red reset button. (See § 7.4).

Determine if all power supplies are operational and all fuses are intact. If the power supplies are OK but the display is blank, check the watch dog output (pin 12, U5g). A high output here will blank the display, turn on the humidifier fault LED indicator and isolate the heater circuits but not necessarily stop the processor. Check for the presence of a 33 to 40 ms period square wave at PB7 (pin 1 U5b). If the watch dog output is high and the 33 to 40 ms clock is present a fault in the watch dog circuitry is indicated but if port PB7 is not changing state there is a fault elsewhere.

7.6SCREW TORQUE SETTINGS

Below is a guide to screw torques used on the humidifier, use this as a guide for tightening of screws on the humidifier (exact torques are not required).

Ref	Screw	Application	Driver	Torque(in/oz)	Torque
					(Nm)
	CHASSIS
14	Screw #8 x ½" Pan Phil TY25 S/S	Case Front/Body	Phillips	85-113	0.6 to
					0.8
18	Screw M4 x 8 Pan Phil Taptite	Chassis Earth Screws	Phillips	240-270	1.7 to
					1.9
21	Screw M6 x 25 Csk Allen S/S	Mounting Bracket	Allen	248-276	1.75 to
					1.95
22	Screw M4 x 14 Pan Pozi Taptite	Mains Cord Clamp	Pozidriv	198-240	1.4 to
			e		1.7
26	Screw M6 x 16 Allen S/S Button	Chassis Earth Screw	Allen	248-276	1.75 to
	Head				1.95
27	Screw M3 x 5 Pan Phil Taptite	Heaterplate Standoffs	Phillips	99-113	0.7 to
					0.8
	HEATERPLATE
2	Screw M4 x 8 Pan Phil Taptite	Heaterplate	Phillips	212-254	1.5 to
		Earth/Element			1.8
5	Screw M3 x 5 Pan Phil Taptite	Thermistor/Thermostat	Phillips	99-113	0.7to 0.8
		Heaterplate

Ref. 185040646 MR730/720/700/480 Technical Manual ¯ Revision F ¯ Issued March 2001