Sharp R-2277 Service Manual page 17

PROCEDURE
LETTER
Resistance of Blower motor should be approximately 52Ω.
Resistance of Stirrer motor should be approximately 8.8 kΩ.
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
M NOISE FILTER TEST
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.
N
L
MEASURING POINT
Between N and L
Between terminal N and WHITW
Between terminal L and BLK
If incorrect readings are absorbed, replace the noise filter.
CARRY OUT 4R CHECKS
N CONTROL PANEL ASSEMBLY TEST
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 two
units, Control Unit and Switch Unit, troubleshooting by unit replacement is described according to
the symptoms indicated.
1. Switch Unit
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the select buttons, a certain button produces no signal at all.
b) When touching the select buttons, sometimes a button produces no signal.
2. Control Unit
The following symptoms may indicate a defective control unit. Replacing the control unit.
2-1 Programming problems.
a) When touching the select buttons, a certain group of buttons do not produce a signal.
2-2 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.
2-3 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
Note: When defective components, (the Control Unit or Switch Unit) are replaed, the defective part
or parts must be properly packed for return in the shipping carton. with its cushion material,
in which the new replacement part was shipped to you.
TEST PROCEDURES
WHT
L
F1
Cx
L
Cy
BLK
15
COMPONENT TEST
L (min)
0.5mH
INDICATION OF OHMMETER
Open circuit
Short circuit
Short circuit
R-2277
R-2287
Cx ± 20% Cy ± 20%
0.22 µF
4700 pF