Procedure J: Motor Winding Test; Procedure K: High Voltage Fuse Test; Procedure L: Noise Filter Test; Procedure M: Touch Control Panel Assembly Test - Sharp R-990KS Service Manual

R990K(W)
Room Temp...................20°C - 30°C
Resistance.....................Approx. 350kΩ - 155kΩ
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.

[10] Procedure J: MOTOR WINDING TEST

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
Approximately 295 Ω
Fan motor
Turntable motor Approximately 19.2 kΩ
Approximately 210 Ω
Convection fan motor
Damper motor Approximately 11 kΩ
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.

[11] Procedure K: HIGH VOLTAGE FUSE TEST

CARRY OUT 3D CHECKS.
If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.
Check them and replace the defective parts and the high voltage fuse.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE REPLACEMENT.

[12] Procedure L: NOISE FILTER TEST

CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise filter. Using an ohmmeter, check
between the terminals as described in the following table. If incorrect readings are
obtained, replace the noise filter unit.
MEASURING POINT
Between N and L
Between terminal N and WHITE
Between terminal L and RED
CARRY OUT 4R CHECKS.
[13] Procedure M: 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, the touch control panel assembly is divided into two
units, Control Unit and Key Unit and troubleshooting by unit replacement is described according to the symptoms indicated.
1. Key Unit. Note: Check key unit ribbon connection before replacement.
The following symptoms indicate a defective key unit. Replace the key unit.
1) When touching the pads, a certain pad produces no signal at all.
2) When touching a number pad, two figures or more are displayed.
3) When touching the pads, sometimes a pad produces no signal.
2. Control Unit.
The following symptoms indicate a defective control unit. Replace the control unit. Before replacing the control unit, perform the Key unit test (Pro-
cedure N) to determine if control unit is faulty.
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) 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.
Resistance
INDICATION OF OHMMETER
Open circuit
Short circuit
Short circuit
N
NOISE SUPPRESSION COIL
LINE BYPASS CAPACITOR
0.0022μ /AC 250V
WHT
8 – 4
NOISE FILTER
LINE CROSS CAPACITOR 0.22μ / AC 250V
LINE BYPASS CAPACITOR
0.0022μ /AC 250V
L
FUSE
F10A
RED