R-23AM. Revised (including ) - Sharp Home Appliance Service Manual (repair manual). Page 15

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If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

If incorrect readings are absorbed, replace the noise filter.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of noise filter. Using an ohmmeter, check between the
terminals as described in the following table.

Between N and L

Approx. 680 k

Ω

Between terminal N and WHIT

Short circuit

Between terminal L and BLK

Short circuit

CARRY OUT 3D CHECKS.

If the high voltage fuse F4 (or F5) is blown, there could be a short in the  high voltage rectifier or the magnetron
MG1 (or MG2). Check them and replace the defective parts and the high voltage fuse F4 (or F5).

CARRY OUT 4R CHECKS.

F3 : WEAK POINT

NOISE FILTER

NOISE SUPPRESSION COIL

DISCHARGE RESISTOR 680 k

Ω 1/2W

DISCHARGE RESISTOR 10 M

Ω 1/2W

LINE CROSS CAPACITOR 0.22

µF/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

L

BLK

WHT

N

The touch control panel consists of circuits including semiconductors such as LSI etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a
voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into three
units, Control Unit,  Switch Unit and Encoder Unit troubleshooting by unit replacement is described
according to the symptoms indicated.
1. Switch Unit    Note : Check the lead wire harness connections among big and small switch units

and control unit before replacement.

The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching the buttons, sometimes a button produces no signal.

2. Encoder        Note : Check the lead wire connection between encoder and control unit before

replacement.

The following symptoms indicate a defective encoder. Replace the encoder.
a) When rotating the encoder, the cooking time can not be entered.

3. Control Unit

The following symptoms may indicate a defective control unit. Replacing the control unit. Before
replacing the control unit, perform the switch unit test (Procedure N) to determine if control unit is
faulty.

3-1 Programming problems.

a) When touching the buttons, a certain group of buttons do not produce a signal.

3-2 Display problems.

a) For a certain digit, all or some segments do not light up.
b) For 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.

3-3 Other possible problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.