Sharp R-450C, Service Manual

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14
R-450C
TOUCH CONTROL PANEL ASSEMBLY
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.
Key Unit
The key unit is composed of a matrix, signals generated
in the LSI are sent to the key unit through P10-P17.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through AN11,
AN10, AN9, P42, P41 and AN8 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, synchro-
nizing signal circuit and back light circuit.
1) ACL
This circuit generates a signal which resets the LSI to
the initial state when power is supplied.
2) Indicator Circuit
This circuit consists of 40 segments and 16 common
electrodes using a Liquid Crystal Display.
The Liquid Crystal Display (LCD) is drived by LCD
driver IC3.
3) Power Source Circuit
This circuit generates voltages necessary in the con-
trol 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 -5V LSI(IC1)
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 clock
circuit.
It accompanies a very small error because it works on
commercial frequency.
7) Door Sensing 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 diodes
LD10-LD19).