Electrolux MC2660E (EU) Service Manual page 20

J TOUCH CONTROL PANEL ASSEMBLY TEST
K SWITCH UNIT TEST
SOI 05.06 FV
TEST PROCEDURES
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 four units,
Control unit, Switch Unit, LED Unit and Relay Unit. Troubleshooting by unit
replacement is described according to the symptoms indicated.
1. Switch Unit. NOTE: Check switch unit lead wire harness connection
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. Before replace
the control unit, perform the switch unit test (Procedure L) 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.
If the display fails to clear when the STOP key is depressed, first verify the lead
wire harness is marking good contact, verify that the stop switch operates properly;
that is the contacts are closed when the door is closed and open when the door is
open. If the stop switch is good, disconnect the lead wire harness that connects the
switch unit to the control unit and make sure the stop switch is closed (either close
the door or short the stop switch connecter). Use the switch unit matrix indicated on
the switch unit circuit and place a jumper wire between the pins that correspond to
the STOP key making momentary contact. If the control unit responds by clearing
with a beep the switch unit is faulty and must be replaced. If the control unit does
not respond, it is a faulty and must be replaced. If a specific key does not respond,
the above method may be used (after clearing the control unit) to determine if the
control unit or switch unit is at fault.
before replacement.
20/34 599 36 78-44