R-4G75M (serv.man3). Section 2 Test procedures, LSI table (page 8-22) - Sharp Home Appliance Service Manual (repair manual). Page 6

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If incorrect readings are obtained, replace the monitor resistor.

CARRY OUT 4R CHECKS

CARRY OUT 3D CHECKS

Disconnect the leads from the motor. Using an ohmmeter, check
the resistance between the two terminals as described in the table
below.

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately 200

Ω

Turntable motor

Approximately 15.5k

Ω

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS

Table: Resistance

Resistor

Resistance

Monitor resistor

 Approx. 0.8

Ω

CARRY OUT 3D CHECKS

Before carrying out the following tests make sure the heating element is cool completely.
1. Resistance of heating element

Disconnect the wire leads to the heating element to be tested. Using ohmmeter with low resistance
range. Check the resistance across the terminals of the heating element as described in the following
table.

Table: Resistance of heating element

Parts name

Resistance

Grill heater

Approximately 29

Ω

 x 2 = 58

Ω

2. Insulation resistance

Disconnect the wire leads to the heater element to be tested, Check the insulation resistance
between the element terminal and cavity using a 500V - 100M

Ω

 insulation tester. The insulation

resistance should be more than 10M

Ω

 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
sholud be replaced.

CARRY OUT 4R CHECKS

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, the touch control panel assembly is divided into two units, Control Unit and
Key  Unit, and troubleshooting by replacement is described according to the symptoms indicated.
1.  Key Unit

The following symptoms indicate a defective key unit. Replace the key unit.
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.

2.  Control Unit

The following symptoms  indicate a defective control unit.  Replacing the control unit.