SOI 12.06 FV 30/43 599 37 42-75
SERVICING
1. 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
containing them in aluminium foil.
2) When soldering, ground the technician as
shown in the figure and use grounded soldering
iron and work table.
2. Servicing of Touch Control Panel
We describe the 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.
(1) Servicing the touch control panel with
power line 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 outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
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 the performance of the touch control
panel,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) Re-connect the leads to the primary of the
power transformer.
4) Re-install the outer case (cabinet).
5) Re-connect 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 is long
enough that they may be separated from each other.
For those models, therefore, it is possible to check
and repair the controls of the touch control panel
while keeping it apart from the oven; in this case you
must short both ends of the door sensing switch (on
PWB) of the touch control panel with a jumper, which
brings about 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 the dummy resistor(s) with resistance
equal to that of the controls are used.
(2) Servicing the touch control panel with power supply
from an external power source:
Disconnect the touch control panel completely from
the oven, and short both ends of the door sensing
switch (SW3: STOP SWITC on PWB) of the touch
control panel, which activates 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.
3. Servicing Tools
Tools required to service the touch control panel
assembly.
1) Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)
2) Others: Hand tools
4. Other Precautions
1) Before turning on the 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.
approx. 1 M ohm
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