Sharp R-930CS Service Manual page 32

R-930CS
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 imped-
ance 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 some-
times 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. Shapes of Electronic Components
Transistor
B
C
E 2SB910M
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
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 trans-
former.
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 trans-
former.
4) Re-install the outer case (cabinet).
TOUCH CONTROL PANEL SERVICING
approx. 1M ohm
Transistor
DTA123ES
KRA101M
KRA223M
KRC243M
C B
E
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 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).
4. 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) Oscilloscope: Single beam, frequency range: DC-10MHz
type or more advanced model.
3) Others: Hand tools
5. 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.
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