Servicing The Touch Control Panel - Electrolux EI27MO45GSA Technical & Service Manual

Component Teardown

Servicing The Touch Control Panel

Precautions For Handling Electronic Components
This unit uses CMOS LSI in the integral part of the
circuits. When handling these parts, the following
precautions should be strictly followed. CMOS LSI have
extremely high impedance at its input and output
terminals. For this reason, it is easily influenced by the
surrounding high voltage power source, static electricity
charge in clothes, etc. and sometimes it is not fully
protected by the built-in protection circuit.
In order to protect CMOS LSI.
1. When storing and transporting, thoroughly wrap
them in aluminium foil. Also wrap all PW boards in
aluminium foil.
2. When soldering, ground the technician and use a
grounded soldering iron and work table.
Servicing of Touch Control Panel
The following are procedures to permit servicing of the
touch control panel of the microwave oven and the
precautions you must take when doing so. To perform
the servicing, power to the touch control panel is
available either from the power line of the oven itself or
from an external power source.
A. Servicing the touch control panel with power
supply of the oven:
Therefore, before checking the performance of the touch
control panel:
1. Disconnect the power supply cord and then remove
the outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect leads to the primary of power transformer.
5. Ensure leads remain isolated from other components
and oven chassis by using insulation tape.
6. Re-connect the power supply cord.
After checking performance of the touch control panel:
1. Disconnect the power supply cord.
2. Open the door and block it open.
3. Reconnect leads to the primary of power transformer.
4. Reinstall the outer case (cabinet).
5. Reconnect the power supply cord after the outer
case is installed.
6. Run the oven and check all functions.
a) On some models, the power supply cord between
the touch control panel and the oven itself is so
short that the two can't be separated. For those
models, check and repair all the controls (sensor
related ones included) of the touch control panel
while keeping it connected to the oven.
b) On some models, the power supply cord between
the touch control panel and the oven proper is long
enough that they may be separated from each other.
For those models, it is possible to check and repair
the controls of the touch control panel while keeping
it apart from the oven proper; in this case you must
short both ends of the door sensing switch (on PWB)
of the touch control panel with a jumper, which
activates an operational state that is equivalent to
the oven door being closed. As for the sensor-related
controls of the touch control panel, checking them is
possible if dummy resistor(s) with resistance equal to
that of the controls are used.
B. Servicing the touch control panel with power
supply from an external power source:
Disconnect the touch control panel completely from the
oven proper, and short both ends of the door sensing
switch (on PWB) of the touch control panel, which brings
about an operational state that is equivalent to the oven
door being closed. Connect an external power source to
the power input terminal of the touch control panel, then
it is possible to check and repair the controls of the touch
control panel; it is also possible to check the sensor
related controls of the touch control panel by using the
dummy resistor(s).
Servicing Tools
Tools required to service touch control panel assembly.
1. Soldering iron: 30W (It is recommended to use a
soldering iron with a grounding terminal.)
2. Oscilloscope: Single beam, frequency range:
DC - 10MHz type or more advanced model.
3. Others: Hand tools
Other Precautions
1. Before turning on power source of the control unit,
remove the aluminium foil applied for preventing
static electricity.
2. Connect the connectors of the key unit to the control
unit, being sure that the lead wires are not twisted.
3. After aluminium foil is removed, be careful that
abnormal voltage due to static electricity etc. is not
applied to the input or output terminals.
4. Attach connectors, electrolytic capacitors, etc. to
PWB, making sure that all connections are tight.
5. Be sure to use specified components where high
precision is required.
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