Sharp R-770AM Service Manual ▷ View online
8
770AM -
PROCEDURE
LETTER
COMPONENT TEST
C
RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate 230/240 volts, if not check oven circuit.
the control unit with an A.C. voltmeter.
The meter should indicate 230/240 volts, if not check oven circuit.
Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
convection cooking operation or grill operation.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
convection cooking operation or grill operation.
DC. voltage indicated .......... Defective relay.
DC. voltage not indicated .... Check diode which is connected to the relay coil. If diode is good,
DC. voltage not indicated .... Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
Approx. 24.0V D.C.
Oven lamp / Turntable motor
RY2
Approx. 24.0V D.C.
High voltage transformer
RY3
Approx. 24.0V D.C.
Grill heating element (Top grill)
RY4
Approx. 24.0V D.C.
Bottom heating element
RY5
Approx. 24.0V D.C.
Fan motor
CARRY OUT 4R CHECKS.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit
on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
OCCURANCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present at
Check supply voltage and oven power cord.
Power terminal of CPU connector (CN-A).
2
The rated AC voltage is present at primary
Low voltage transformer or secondary circuit defective.
side of low voltage transformer.
Check and repair.
3
Only pattern at "a" is broken.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4
Pattern at "a" and "b" are broken.
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
D
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD (PWB) IS OPEN.
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for burn-
ing damage and examine the trans-
former with tester for the presence of
layer short circuit (check primary coil
resistance).
If any abnormal condition is detected,
replace the defective parts.
ing damage and examine the trans-
former with tester for the presence of
layer short circuit (check primary coil
resistance).
If any abnormal condition is detected,
replace the defective parts.
CARRY OUT 4R CHECKS.
(J1)
a
c
b
d
CN -A
RY1
D21
T1
VRS1
1
TEST PROCEDURES
9
770AM -
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units as
shown in the touch control panel circuit.
shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit
(2) Control Unit
The principal functions of these units and signals commu-
nicated among them are explained below.
nicated 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 P23 - P27.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through P74 - P77
to perform the function that was requested.
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit through P23 - P27.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through P74 - P77
to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit, tempera-
ture measurement circuit, indicator circuit, encoder circuit
and back light circuit.
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit, tempera-
ture measurement circuit, indicator circuit, encoder circuit
and back light circuit.
1) LSI
This LSI controls the temperature measurement sig-
nal, the key strobe signal, relay driving signal for oven
function and indicator signal.
nal, the key strobe signal, relay driving signal for oven
function and indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control
unit.
unit.
Symbol
Voltage
Application
VC
-5.2V
LSI(IC1)
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.
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 signals which resets the LSI to
the initial state when power is supplied.
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).
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, heating element, fan motor,
turntable motor and light the oven lamp.
turntable motor and light the oven lamp.
8) Encoder
The encoder converts the signal generated by LSI into
the pulse signal, and the pulse signal is returned to the
LSI.
the pulse signal, and the pulse signal is returned to the
LSI.
9) Back Light Circuit
A circuit to drive the back light (Light emitting diodes
LD1 - LD5).
LD1 - LD5).
10) Indicator Circuit
This circuit consists of 4-digits, 30-segments and 3-
common electrodes using a Liquid Crystal Display.
common electrodes using a Liquid Crystal Display.
11) Temperature Measurement Circuit
The temperature in the oven cavity is sensed by the
thermistor.
The variation of resistance according to sensed tem-
perature is detected by the temperature measurement
circuit and the result applied to LSI.
The result of detecting is given to LSI controlling the
relay and display.
thermistor.
The variation of resistance according to sensed tem-
perature is detected by the temperature measurement
circuit and the result applied to LSI.
The result of detecting is given to LSI controlling the
relay and display.
10
770AM -
1
C1
IN
Terminal not used.
2
VL1
IN
Power source voltage input terminal.
Standard voltage for LCD.
Standard voltage for LCD.
3-6
AN7-AN4
IN
Terminal to change cooking constant.
7
AN3
IN
Terminal not used.
8
AN2
IN
Input signal which communicates the door open/close information to LSI.
Door closed; "H" level signal.
Door opened; "L" level signal.
Door closed; "H" level signal.
Door opened; "L" level signal.
9
AN1
IN
Terminal not used.
10
AN0
IN
Temperature measurement input: OVEN THERMISTOR.
By inputting DC voltage corresponding to the temperature detected by the
thermistor, this input is converted temperature by the A/D converter built into the
LSI.
By inputting DC voltage corresponding to the temperature detected by the
thermistor, this input is converted temperature by the A/D converter built into the
LSI.
11-12
P57-P56
OUT
Timing signal output terminal for temperature measurement (OVEN).
"L" level (-5V) : Temperature measuring timing. (Oven cooking)
"H" level (GND) : Thermistor open timing.
"L" level (-5V) : Temperature measuring timing. (Oven cooking)
"H" level (GND) : Thermistor open timing.
13
P55
OUT
Fan motor driving signal.
To turn on and off the fan motor relay
RY5. "L" level during cooking, or for 5
minutes or more after grill cooking or
dual cooking. "H" level otherwise.
To turn on and off the fan motor relay
RY5. "L" level during cooking, or for 5
minutes or more after grill cooking or
dual cooking. "H" level otherwise.
14
CNTR0
OUT
Signal to sound buzzer.
A: key touch sound.
B: Completion sound.
C: When the temperature of the oven cavity
A: key touch sound.
B: Completion sound.
C: When the temperature of the oven cavity
reaches the preset temperature in the
preheating mode, or when the
preheating hold time (30 minutes) is
elapsed.
preheating mode, or when the
preheating hold time (30 minutes) is
elapsed.
15
P53
OUT
Oven lamp and turntable motor driving signal(Square Waveform : 50Hz).
To turn on and off shut-off relay (RY1). The
square waveform voltage is delivered to
the relay (RY1) driving circuit and relays
(RY2,RY3,RY4) control circuit.
To turn on and off shut-off relay (RY1). The
square waveform voltage is delivered to
the relay (RY1) driving circuit and relays
(RY2,RY3,RY4) control circuit.
16
P52
OUT
Bottom heating element driving signal.
To turn on and off the bottom element relay
(RY4). "L" level during grill (BOTTOM
HEATER, TOP AND BOTTOM) cooking or
dual (Dual 2) cooking; "H" level otherwise.
To turn on and off the bottom element relay
(RY4). "L" level during grill (BOTTOM
HEATER, TOP AND BOTTOM) cooking or
dual (Dual 2) cooking; "H" level otherwise.
17
P51
OUT
Grill heating element (TOP GRILL) driving signal.
To turn on and off the grill heating element
relay (RY3). "L" level during grill (TOP
GRILL, TOP AND BOTTOM) cooking or
dual (Dual 1) cooking; "H" level otherwise.
To turn on and off the grill heating element
relay (RY3). "L" level during grill (TOP
GRILL, TOP AND BOTTOM) cooking or
dual (Dual 1) cooking; "H" level otherwise.
18
P50
OUT
Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay
(RY2). In 100% POWER
operation, the signals hold "L"
level during microwave cooking
and "H" level while not cooking.
In other cooking modes (70%,
50%, 30%, 10%) the signal turns
to "H" level and "L" level in
repetition according to the power
level.
To turn on and off the cook relay
(RY2). In 100% POWER
operation, the signals hold "L"
level during microwave cooking
and "H" level while not cooking.
In other cooking modes (70%,
50%, 30%, 10%) the signal turns
to "H" level and "L" level in
repetition according to the power
level.
19-20
P47-P46
IN/OUT
Terminal not used.
LSI(IZA799DR)
The I/O signal of the LSI(IZA799DR) are detailed in the following table.
The I/O signal of the LSI(IZA799DR) are detailed in the following table.
Pin No.
Signal
I/O
Description
ON
OFF
During cooking, or for 5 minutes or more
after grill cooking or dual cooking
after grill cooking or dual cooking
L
GND
H.
A
B
C
H: GND
L
0.12 sec
2.4 sec
1.2 sec
1.2 sec
20 msec
During cooking
H
L
ON
OFF
During
cooking
L
GND
H.
(Grill or dual)
ON
OFF
During
cooking
L
GND
H.
(Grill or dual)
ON/OFF time ratio in Micro
cooking
(a. 32second time base)
cooking
(a. 32second time base)
ON/OFF time ratio in Micro
cooking
(a. 48second time base)
cooking
(a. 48second time base)
MICRO
ON
OFF
COOK
100%
100%
32sec.
0sec.
70%
24sec.
8sec.
50%
18sec.
14sec.
30%
12sec.
20sec.
10%
6sec.
26sec.
MICRO
ON
OFF
COOK
100%
100%
48sec.
0sec.
70%
36sec.
12sec.
50%
26sec.
22sec.
30%
16sec.
32sec.
10%
8sec.
40sec.
TOUCH CONTROL / DESCRIPTION OF LSI
11
770AM -
TOUCH CONTROL /
DESCRIPTION OF LSI
Pin No.
Signal
I/O
Description
20 msec
H : GND
L (-5V)
21
P45
OUT
Back light driving signal.
To change the brightness of the back light (Light emitting diodes LD1 - LD5). The
square waveform voltage is delivered to the back light driving circuit.
To change the brightness of the back light (Light emitting diodes LD1 - LD5). The
square waveform voltage is delivered to the back light driving circuit.
22
P44
IN/OUT
Terminal not used.
23
INT1
IN
Signal coming from encoder.
When the encoder is turned, the contacts of encoder make pluse signals. And
pulse signals are input into INT1.
When the encoder is turned, the contacts of encoder make pluse signals. And
pulse signals are input into INT1.
24
INT0
IN
Signal to synchronized LSI with commercial power source
frequency(50Hz).
frequency(50Hz).
This is basic timing for time processing of LSI.
25
P41
IN
Signal coming from encoder.
Signal similar to INT1. Pulse signals are input into P41.
Signal similar to INT1. Pulse signals are input into P41.
26
P40
IN/OUT
Terminal not used.
27
P77
IN
Signal coming from touch key.
When any one of G11 line keys on key matrix is touched, a corresponding signal
from P23 - P27 will be input into P77. When no key is touched, the signal is held
at "L" level.
When any one of G11 line keys on key matrix is touched, a corresponding signal
from P23 - P27 will be input into P77. When no key is touched, the signal is held
at "L" level.
28
P76
IN
Signal similar to P77.
When any one of G7 line keys on key matrix is touched, a corresponding signal will
be input into P76.
When any one of G7 line keys on key matrix is touched, a corresponding signal will
be input into P76.
29
P75
IN
Signal similar to P77.
When any one of G5 and G9 line keys on key matrix is touched, a corresponding
signal will be input into P75.
When any one of G5 and G9 line keys on key matrix is touched, a corresponding
signal will be input into P75.
30
P74
IN
Signal similar to P77.
When any one of G2 line keys on key matrix is touched, a corresponding signal will
be input into P74.
When any one of G2 line keys on key matrix is touched, a corresponding signal will
be input into P74.
31-33
P73-P71
IN/OUT
Terminal not used.
34
P70
IN
Connected to VC.
35
RESET
IN
Auto clear terminal.
Signal is input to reset the LSI to the initial state when power is applied. Temporarily
set to "L" level the moment power is applied, at this time the LSI is reset. Thereafter
set at "H" level.
Signal is input to reset the LSI to the initial state when power is applied. Temporarily
set to "L" level the moment power is applied, at this time the LSI is reset. Thereafter
set at "H" level.
36
XCIN
IN
Terminal not used.
37
XCOUT
OUT
Terminal not used.
38
XIN
IN
Internal clock oscillation frequency input setting.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit
with respect to XIN terminal.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit
with respect to XIN terminal.
39
XOUT
OUT
Internal clock oscillation frequency control output.
Output to control oscillation input of XOUT.
Output to control oscillation input of XOUT.
40
VSS
IN
Power source voltage: -5V.
VC voltage of power source circuit input.
VC voltage of power source circuit input.
41
P27
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G4 and G12 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G4 and G12 line keys on matrix is touched.
42
P26
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G10 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G10 line keys on matrix is touched.
43
P25
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G6 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P74 - P77 terminal
while one of G6 line keys on matrix is touched.
44
P24
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P74 - P77
terminal while one of G3 and G8 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P74 - P77
terminal while one of G3 and G8 line keys on matrix is touched.
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