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CHAPTER 9.

R395N(S)

TOUCH CONTROL PANEL ASSEMBLY

[1] OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following units.

(1) Key Unit

(2) Control Unit (The Control Unit consists of Power Unit and LSI Unit).

The principal functions of these units and the signals communicated among them are explained below.

1. Key Unit

The key unit is composed of a matrix, signals generated in the LSI are sent to the key unit through P51-P57.When a key pad is touched, a signal is

completed through the key unit and passed back to the LSI through AN2 - AN5 to perform the function that was requested.

2. Control Unit

Control unit consists of LSI, reset circuit, indicator circuit, power source circuit, relay circuit, buzzer circuit, synchronizing signal circuit, absolute

humidity sensor circuit and back light circuit.

1) Reset Circuit

This circuit generates a signal which resets the LSI to the initial state when power is supplied.

2) Indicator Circuit

This circuit consists of 25 segments and 4 common electrodes using a Liquid Crystal Display.

3) Power Source Circuit

This circuit generates voltages necessary in the control unit from the AC line voltage.In addition, the synchronizing signal is available in order to

compose a basic standard time in the clock circuit.

4) Relay Circuit

A circuit to drive the magnetron, fan motor, turntable motor and light the oven lamp.

5) Buzzer Circuit

The buzzer is responsive to signals from the LSI to emit audible sounds (key touch sound and completion sound).

6) Synchronizing Signal Circuit

The power source synchronizing signal is available in order to compose a basic standard time in the clockcircuit.It accompanies a very small error

because it works on commercial frequency.

7) 2nd. Interlock Relay Control Switch

A switch to "tell" the LSI if the door is open or closed.

8) Back Light Circuit

A circuit to drive the back light (Light emitting diodesLD1- LD4).

[2] SERVICING FOR TOUCH CONTROL PANEL

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.

2) When soldering, ground the technician as shown in the figure and use grounded soldering iron and work table.

2. 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 HAZ-

ARD.

Therefore, before checking the performance of the touch control panel,

approx. 1M ohm

9 – 1

R395N(S)