R-90GCK (serv.man7). Test procedure - Sharp Home Appliance Service Manual (repair manual). Page 4

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1. CARRY OUT 3D CHECKS.
2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless

the temperature of the magnetron reaches approximately 150˚C. An open temperature fuse
indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially
the cooling duct and cooling fan.

3. CARRY OUT 4R CHECKS.

CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERA-

TURE, REPLACE TEMPERATURE FUSE.

1. CARRY OUT 3D CHECKS.
2. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the

temperature of the thermal cut-out reaches approximately 170˚C. The thermal cut-out resets
automatically at approximately 155˚C. If thermal cut-out has opened under normal condition,
replace the same item as in the parts list.
An open thermal cut-out indicates overheating of the top heating element unit. Check for restricted
air flow to the top heat element  unit through the vent holes of the oven cavity, especially the heater
duct upper and convection fan.

3. CARRY OUT 4R CHECKS.

CAUTION: IF THE THERMAL CUT-OUT INDICATES AN OPEN CIRCUIT AT ROOM TEMPERA-

TURE, REPLACE THERMAL CUT-OUT.

1. CARRY OUT 3D CHECKS.
2. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the

temperature of the thermal cut-out reaches approximately 150˚C. The thermal cut-out resets
automatically at approximately 130˚C. If thermal cut-out has opened under normal condition,
replace the same item as in the parts list.
An open thermal cut-out indicates overheating of the side heating element unit. Check for
restricted air flow to the side heat element  unit through the vent holes of the oven cavity, especially
the heater duct left and convection fan.

3. CARRY OUT 4R CHECKS.

CAUTION: IF THE THERMAL CUT-OUT INDICATES AN OPEN CIRCUIT AT ROOM TEMPERA-

TURE, REPLACE THERMAL CUT-OUT.

1. CARRY OUT 3D CHECKS.
2. Make sure the heating element is fully cooled and test as follows;

a. Disconnect wire leads from the heating element and measure the resistance with an ohmmeter.

On the R x 1 scale, the resistance between the heating element terminals should be approximately
37.2

Ω

.

b. Disconnect wire leads from the heating element  and measure the insulation resistance with

500V - 100M

Ω

 insulation resistance meter. The insulation resistance between heating element

terminal and cavity should be more than 0.5M

Ω

.

3. If the meter does not indicate above resistance, replace the top heating element.
4. CARRY OUT 4R CHECKS.

1. CARRY OUT 3D CHECKS.
2. Make sure the heating element is fully cooled and test as follows;

a. Disconnect wire leads from the heating element and measure the resistance with an ohmmeter. On the

R x 1 scale, the resistance between the heating element terminals should be approximately 55.7 

Ω

.