Sharp R-300BW Service Manual page 19

Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit, encoder
circuit, indicator circuit and potentiometer circuit.
1) LSI
This LSI controls the encoder signal, potentiometer
signal, relay driving signal for oven function, buzzer
signal and LED signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control
unit.
Symbol Voltage
VC -5.0V
3) 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.
4) ACL
A circuit to generate a signal which resets the LSI to the
initial state when power is supplied.
CONTROL PANEL ASSEMBLY
OUTLINE OF CONTROL PANEL
Application
LSI(I-1)
17
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion sound).
6) Door Sensing Switch (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 and
light the oven lamp.
8) Encoder
The encoder generates the pulse signal, and the pulse
signal is sent to the LSI.
9) Indicator Circuit
Indicator elements are the Light-emitting diodes (LD1-
LD24).
This circuit consists of 4-digits and 6 segments.
10) Potentiometer Circuit
The circuit makes setting of the power level by variable
resistance.
R-300BW