Electrolux MC1751E - J Touch Control Panel Assembly Test

SOI 01.05 FV 19/33 599 36 78-06
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
If a reading of the line voltage was obtained (step 7) but the motor was not
turning then it is faulty and should be replaced. If the meter indicated that the
no supply was present then the winding to the motor should be checked for
continuity or other circuit checks should be made, i.e. relays, switches.
J
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 can not be performed with only a voltmeter and ohmmeter.
In this service manual, the touch control panel assembly is in three units,
Control unit, Switch Unit, and LED Unit. Troubleshooting by unit replacement is
described according to the symptoms indicated.
Control Panel.
The following symptoms indicate a defective control unit.
1. Switch Unit. NOTE: Check switch unit lead wire harness connection
before replacement.
The following symptoms indicate a defective switch unit. Replace the
switch unit.
a) When touching the keys, a certain key produces no signal at all.
b) When touching a key, two figures or more are displayed.
c) When touching the keys, sometimes a key produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Replace the
control unit, perform the switch unit test(Procedure K) to determine if
control unit is faulty.
2-1 In connection with keys.
a) When touching a key, a certain group of keys do not produce a signal.
b) When touching a key, no keys produce a signal.
2-2.In connection with indicators.
a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding dots 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.
h) When touching a tact switch, the control unit does not respond.
2-3.Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
3. LED Unit
a) No backlight behind display.
b) Dull backlight behind display.