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
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.
approx. 1M ohm
2. Shapes of Electronic Components
Transistor
KRC243M
EC B
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 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,
After checking the performance of the touch control panel,
1)Disconnect the power supply cord.
2)Open the door and block it open.
3)
transformer.
4)
5)
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
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
(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
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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