Sharp R-1880LS Service Manual page 38

R-1880LS/LST
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.
) When soldering, ground the technician as shown in the figure
and use grounded soldering iron and work table.
2. Shapes of Electronic Components
Transistor
2SB1238
B
C
E
3. 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 MI-
CROWAVE OVEN IS STILL LIVE DURING SERVICING
PRESENTS A HAZARD.
Therefore, when checking the performance of the touch control
panel, put the outer cabinet on the oven to avoid touching the
high voltage transformer, or unplug the primary terminal (con-
nector) of the high voltage transformer to turn it off; the end
of such connector must be insulated with an insulating tape.
After servicing, be sure to replace the leads to their original
locations.
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-re-
lated 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, therefore, 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)
SERVICING
(2) Servicing the touch control panel with power supply
4. Servicing Tools
approx. 1M ohm
1) Soldering iron: 30W
) Oscilloscope: Single beam, frequency range: DC - 10MHz type
3) Others: Hand tools
Transistor
DTA123ES
5. Other Precautions
KRA101M
1) Before turning on the power source of the control unit, remove
KRC101M
KRC243M
C B
) Connect the connector of the key unit to the control unit being
E
3) After aluminium foil is removed, be careful that abnormal
4) A ttach connectors, electrolytic capacitors, etc. to PWB, making
5) Be sure to use specified components where high precision is
38
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 dummy resistor(s) with
resistance equal to that of the controls are used.
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).
Tools required to service the touch control panel assembly.
(It is recommended to use a soldering iron with a grounding
terminal.)
or more advanced model.
the aluminium foil applied for preventing static electricity.
sure that the lead wires are not twisted.
voltage due to static electricity etc. is not applied to the input
or output terminals.
sure that all connections are tight.
required.