Sharp R-2397 service manual Shapes of Electronic Components, Servicing of Touch Control Panel

R-2397

Pin No.	Signal	I/O	Description
1-3	A0-A2	IN	Connected to GND.
4	VSS	IN	Connected to VC(-5V).
5	SDA	IN/OUT	Serial data input/output : input/outputs data to IC1.
6	SCL	IN	Clock signal input : input/outputs sireal data at every one pulse.
7	TEST	IN	Connected to VC(-5V).
8	VCC	IN	Connected to GND.

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 pre- cautions should be strictly followed. CMOS LSI have extremely high impedance at its input and output termi- nals. 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.

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	Transistor			Transistor
2SB953	2SA1561			DTA114YS
	2SB1238			DTB143ES
E C B	E C B			DTD143ES
		E	C	B KRA101M

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 avail- able 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 PRESENTS A HAZ- ARD.

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 (connector) of the high voltage trans- former 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-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, 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) 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.

(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 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).

4.Servicing Tools

Tools required to service the touch control panel assem- bly.

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 connector 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 preci- sion is required.

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