R-658KM - Sharp Home Appliance Service Manual (repair manual). Page 16

R65

8WM

9 – 1

R657(W)

Service Manual

 

The control section consists of the following units as shown in the
touch control panel circuit.

(1) Key Unit

(2) Control Unit

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

The key unit is composed of a matrix, signals generated in the LSI are
sent to the key unit through P30 - P37. When a key pad is touched, a
signal is completed through the key unit and passed back to the LSI
through P14 - P17 to perform the function that was requested.

Control unit consists of LSI, power source circuit, relay circuit, back
light circuit, synchronizing signal circuit, reset circuit, buzzer circuit,
and indicator circuit.

1) LSI

This LSI controls the tact switch strobe signal, relay driving signal,
for oven function and indicator signal.

2) Power Source Circuit

This circuit generates voltage necessary in the control unit.

3) Synchronizing Signal Circuit

The power source synchronizing signal is available in order to com-
pose a basic standard time in the clock circuit. It accompanies a
very small error because it works on commercial frequency.

4) Reset Circuit

A circuit to generate a signal which resets the LSI to the initial state
when power is supplied.

5) Buzzer Circuit

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

6) Stop Switch

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

7) Relay Circuit

To drive the magnetron, fan motor, turntable motor, heating ele-
ment, and light the oven lamp.

8) Indicator Circuit

This circuit consists of 4-digits, 12-segments and 3-common elec-
trodes using a Liquid Crystal Display.

9) Back Light Circuit

A circuit to drive the back light (Light emitting diodes LD1 - LD4).

Symbol

Voltage

Application

VC

+5V

LSI(IC1)