Sharp R-990KS User Manual

R990K(W)
8 – 3
[5] Procedure E: SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the following table.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R
CHECKS.
[6] Procedure F: FUSE F10A
CARRY OUT 3D CHECKS.
1. If the fuse F10A is blown, there could be shorts or grounds in electrical parts or wire harness. Check them and replace the defective parts or repair
the wire harness.
2. If the fuse F10A is blown when the door is opened, check the upper latch switch, lower latch switch and monitor switch.
If the fuse F10A is blown by incorrect door switching, replace the defective switch(es) and the fuse F10A.
CARRY OUT 4R
CHECKS.
CAUTION: Only replace fuse with the correct value replacement.
[7] Procedure G: TEMPERATURE FUSE AND TERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the temp. fuse or thermal cut-out. Then using an ohmmeter, make a continuity test across the two termi-
nals as described in the table below.
If incorrect readings are obtained, replace the temp. fuse or thermal cut-out.;
An open circuit temperature fuse 150°C (MG)/ thermal cut-out 145°C (MG) indicates that the magnetron has overheated, this may be due to resis-
tricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
An open circuit thermal cut-out 150°C (CONV.) indicates that the convection motor has over heated, this may be due to convection motor locked.
An open circuit thermal cut-out 95°C (FM) indicates that the fan motor winding has overheated, this may be due to blocked ventilation or locked cool-
ing fan.
CARRY OUT 4R
CHECKS.
[8] Procedure H: CONVECTION HEATER TEST
CARRY OUT 3D CHECKS.
Before carrying out the following tests make sure the heater is fully cool.
1. Resistance of heater
Disconnect the wire leads to the heater to be tested. Using ohmmeter with low resistance range.
Check the resistance across the terminals of the heater.
The resistance of heater is approximately 37.5 ohms.
2. Insulation resistance
Disconnect the wire leads to the heater to be tested. Check the insulation resistance between the element and cavity using a 500V - 100M ohms
insulation tester. The insulation resistance should be more than 10M ohms in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heater is probably faulty and should be replaced.
CARRY OUT 4R
CHECKS.
[9] Procedure I: THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect connector-E from the CPU unit. Measure the resistance of the thermistor with an ohmmeter. Connect the ohmmeter leads to Pin No’s E-3
and E-4 of the thermistor harness.
Table: Terminal Connection of Switch
Plunger Operation Common terminal to Normally open terminal Common terminal to Normally close terminal
Released Open circuit Short circuit
Depressed Short circuit Open circuit.
Table: Temperature Fuse and Thermal cut-out Test
Parts Name
Temperature of “ON” condition
(closed circuit).
Temperature of “OFF” condition
(open circuit).
Indication of ohmmeter (When room
temperature is approx. 20°C.)
Temperature fuse 150°C (MG) This is not resetable type. Above 150°C Closed circuit
Thermal cut-out 145°C (MG) This is not resetable type. Above 145°C Closed circuit
Thermal cut-out 150°C (CONV.) Below 130°C Above 150°C Closed circuit
Thermal cut-out 95°C (FAN) Below 75°C Above 95°C Closed circuit

Sharp R-990KS Specifications

General

Brand	Sharp
Model	R-990KS
Category	Microwave Oven
Language	English