Servicing The Touch Control Panel - Electrolux FGMO205KFA Service Manual

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 infl uenced 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:
CAUTION
The high voltage transformer of the microwave
oven is still live during servicing and presents a
hazard.
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.
NOTE
To discharge the high voltage capacitor, wait for 60
seconds and then short-circuit the connection of the
high-voltage capacitor (that is the connecting lead of
the high-voltage rectifier) against the chassis with the
use of an insulated screwdriver.
Section 4 Component Teardown
4. Disconnect the leads to the primary of the power
transformer.
5. Ensure that these leads remain isolated from other
components and oven chassis by using insulation
tape.
6. After that procedure, 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 the leads to the primary of the 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.
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