24
MMD24S
MMD24B
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.
) 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 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,
) 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,
) 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.
TOUCH CONTROL PANEL SERVICING
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.
(2) 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
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 it is also possible to check
the sensor-related controls of the touch control panel
by using the dummy resistor(s).
3. Servicing Tools
Tools required to service the touch control panel
assembly.
) Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)
2) Oscilloscope: Single beam, frequency range: DC-
0MHz type or more advanced model.
3) Others: Hand tools
4. Other Precautions
) 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. M ohm
