R-354M (serv.man4). Complete - Sharp Home Appliance Service Manual (repair manual). Page 9

R354M - 9

The touch control section consists of the following
units.

(1) Key Unit (The key unit consists of a FPC

membrane and a Graphic sheet.)

(2) Control Unit (The Control Unit consists of

Power Unit and CPU Unit).

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

Key Unit
The key unit is composed of a matrix, signals
generated in the LSI are sent to the key unit
through P20, P21, P22, P23, P24, P25, P26 and
P27.
When a key pad is touched, a signal is
completed through the key unit and passed back
to the LSI through P43, P44, P45 and P46 to
perform the function that was requested.

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

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

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

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can
be tested  using an ohmmeter set to its highest range. Connect the ohmmeter across the
terminal of the high voltage rectifier and note the reading obtained. Reverse the meter leads
and note this second reading.
The normal resistance is infinite in one direction and more than 100 k

Ω

 in the other direction.

CARRY OUT 4R CHECKS.

NOTE:

FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE
BATTERIES OF THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT
LEAST 6 VOLTS, BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE
SHOWN IN BOTH DIRECTIONS.

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.

Symbol

Voltage

Application

VC

-5.2V

LSI(IC1)

A circuit to drive the magnetron, fan motor, turnta-
ble motor and  light the oven lamp.

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

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

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

A circuit to drive the back light (Light emitting
diodes LD1- LD5).

OUTLINE OF TOUCH CONTROL PANEL