Sharp R-90GCH Service Manual page 22

R-90GCH
PROCEDURE
LETTER
Difference in power supply voltage will also affect the oven temperature. The Household power supply
voltage may sometimes become lower than the rated voltage and cause under-cooking. If the power
supply voltage is 10% lower than the rated voltage, longer cooking time is required by 10% to 20%.
U MOTOR WINDING TEST
1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL".
3. Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.
If incorrect readings are obtained, replace the motor.
4. CARRY OUT 4R CHECKS.
V TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a
voltmeter and ohmmeter. In this service manual, troubleshooting by unit replacement is described
according to the symptoms indicated.
Before testing,
1) CARRY OUT 3D CHECKS.
2) Disconnect the leads to the primary of the high voltage transformer.
2) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
1. Tact switch
NOTE ;
1) Reinstall the outer case (cabinet).
2) Reconnect the power supply cord after the outer case is installed.
3) Run the oven and check all functions.
The following symptoms indicate a defective tact switch.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
If the tact switch is defective.
1) CARRY OUT 3D CHECKS.
2) Replace the CPU unit.
3) CARRY OUT 4R CHECKS.
2. Control Unit
The following symptoms indicate a defective control unit. Before replacing the control unit,
perform the tact switch test (Procedure W) to determine if control unit is faulty. Reconnect the
power supply cord. And check for followings.
2-1 In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f ) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
TEST PROCEDURES
COMPONENT TEST
Table: Resistance of Motor
Motors
Fan motor FM
Turntable motor TTM
Damper motor DM
20
Resistance
Approximately 77 Ω
Approximately 12 kΩ
Approximately 11 kΩ