Read Sharp R-67STM (serv.man9) Service Manual online
R67STM
9 – 2
[2] SERVICING FOR CONTROL PANEL
1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the circuits. When han-
dling these parts, the following precautions should be strictly followed.
CMOS LSI have extremely high impedance at its input and output ter-
minals. 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.
dling these parts, the following precautions should be strictly followed.
CMOS LSI have extremely high impedance at its input and output ter-
minals. 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 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 control panel
We describe the procedures to permit servicing of the control panel of
the microwave oven and the precautions you must take when doing
so. To perform the servicing, power to the control panel is available
either from the power line of the oven itself or from an external power
source.
the microwave oven and the precautions you must take when doing
so. To perform the servicing, power to the control panel is available
either from the power line of the oven itself or from an external power
source.
1. Servicing the control panel with power supply of the oven:
CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE MICRO-
WAVE OVEN IS STILL LIVE DURING SERVICING AND
PRESENTS A HAZARD.
PRESENTS A HAZARD.
Therefore, before checking the performance of the 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, reconnect the power supply cord.
After checking the performance of the 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 control
panel and the oven itself is so short that the two can't be sepa-
rated. For those models, check and repair all the controls (sen-
sor-related ones included) of the control panel while keeping it
connected to the oven.
rated. For those models, check and repair all the controls (sen-
sor-related ones included) of the control panel while keeping it
connected to the oven.
b) On some models, the power supply cord between the control
panel and the oven proper is long enough that they may be sep-
arated from each other. For those models, therefore, it is possi-
ble to check and repair the controls of the 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 con-
trol panel with a jumper, which brings about an operational state
that is equivalent to the oven door being closed.
arated from each other. For those models, therefore, it is possi-
ble to check and repair the controls of the 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 con-
trol panel with a jumper, which brings about an operational state
that is equivalent to the oven door being closed.
2. Servicing the control panel with power supply from an exter-
nal power source:
Disconnect the control panel completely from the oven, and short
both ends of the door sensing switch (on PWB) of the 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 control panel, then it is possible to check and
repair the controls of the control panel.
both ends of the door sensing switch (on PWB) of the 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 control panel, then it is possible to check and
repair the controls of the control panel.
3. Servicing Tools
Tools required to service the control panel assembly.
1) Soldering iron: 60W
(It is recommended to use a soldering iron with a grounding termi-
nal.)
nal.)
2) Oscilloscope: Single beam, frequency range: DC - 10MHz type or
more advanced model.
3) 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 connector of the switch 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 ter-
minals.
minals.
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. 1M ohm
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