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Model
R-84ST (serv.man3)
Pages
18
Size
796.65 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Part 1 Text(1-18)
File
r-84st-sm3.pdf
Date

Sharp R-84ST (serv.man3) Service Manual ▷ View online

R-84STM - 8
PROCEDURE
LETTER
COMPONENT TEST
A
TOUCH CONTROL PANEL ASSEMBLY TEST
TEST PROCEDURES
B
KEY UNIT TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance can not be performed with only a voltmeter and
ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key Unit,
and also the Control unit is divided into two units, CPU unit and Power unit, and troubleshooting by
replacement is described according to the symptoms indicated.
1.  Key Unit   Note : Check key unit ribbon connection before replacement.
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Panel
The following symptoms indicate a defective control unit. Before replacing the control unit perform the
key unit test (Procedure P) to determine if control unit is faulty.
2-1  In connection with pads
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2  In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3  Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
G 8
G 7
G 6
G 5
G 4
G 3
G 2
G 1
G12
G11
G10
G 9
ROAST BEEF / LAMB
WHOLE POULTRY
CHICKEN QUARTERS
CHICKEN QUARTERS (INSTANT COOK)
ROAST PORK
PASTA DISH
RISOTTO
GRATIN
MEAT JOINT
OVEN CHIPS
ROAST POULTRY
GRILL
MICRO.
POWER
DUAL CONV. /
GRILL
CONV.
( ˚C ) 
DOWN
LESS
MORE
UP
CLEAR
AUTO MINUTE
STOP
START
KITCHEN TIMER
CLOCK SET
KG / LB
CONVERSION
BREAKFAST
BAKED POTATOES
PIZZA
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon
cable is making good contact, verify that the stop switch operates properly; that is the contacts
are closed when the door is closed and open when the door is open. If the stop switch is good,
disconnect the flat ribbon cable that connects the key unit to the control unit and make sure the
stop switch is closed (either close the door or short the stop switch connecter). Use the Key unit
matrix indicated on the control panel schematic and place a jumper wire between the pins that
correspond to the STOP/CLEAR pad making momentary contact. If the control unit responds by
clearing with a beep the key unit is faulty and must be replaced. If the control unit does not
respond, it is faulty and must be replaced.  If a specific pad does not respond, the above method
may be used (after clearing the control unit) to determine if the control unit or key pad is at fault.
CARRY OUT 4R CHECKS.
R-84STM - 9
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
C
RELAY TEST
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.
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.
CARRY OUT 3D CHECKS.
STEPS
OCCURRENCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present between
Check supply voltage and oven power cord.
Pin Nos. 1 and 3 of the 4-pin connector (E).
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.)
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (E) on 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, grill
operation, convection operation or dual operation.
DC. voltage indicated ............. Defective relay.
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. 18.0V D.C.
Oven lamp / Turntable motor
RY2
Approx. 18.0V D.C.
High voltage transformer
RY3
Approx. 24.0V D.C.
Grill (Top) heating element
RY4
Approx. 24.0V D.C.
Bottom heating element
RY5
Approx. 24.0V D.C.
Touch control transformer
RY6
Approx. 24.0V D.C.
Fan motor
RY7
Approx. 24.0V D.C.
Convection motor
CARRY OUT 4R CHECKS.
7
9
1
RY4
(J1)
(J2)
FM
POWER
a
b
c
d
F
CN - E
CN - A
VRS1
RY6
R-84STM - 10
     TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
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, grill heating element, bottom
heating element,  convection motor, fan motor, turntable
motor, touch control transformer and  light the oven lamp.
8) Back Light Circuit
A circuit to drive the back light (Light emitting diodes LD1
- LD10).
9)  Indicator Circuit
This circuit consists 7-digits, 39-segments and 3-common
electrodes using a Liquid Crystal Display.
10) Temperature Measurement Circuit : (OVEN
THERMISTOR)
The temperature in the oven cavity is sensed by the
thermistor. The variation of resistance according to
sensed temperature is detected by the temperature
measurement circuit and the result applied to LSI.
The LSI uses this information to control the relay
and display units.
The touch control section consists of the following units as
shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit (The Control unit consists of Power unit and
CPU unit.)
The principal functions of these units and signals communi-
cated 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 from P40, P41, P72, P73 P74, P75,
P76 and P77.
When a key pad is touched, a signal is completed through the
key unit and passed back to the LSI through P44 - P47 to
perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchroniz-
ing signal circuit, ACL circuit, buzzer circuit, relay circuit,
temperature measurement circuit, indicator circuit and back
light circuit.
1) LSI
This LSI controls the temperature measurement signal,
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.
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.
4) ACL
A circuit to generate a signal which resets the LSI to the
R-84STM - 11
TOUCH CONTROL / DESCRIPTION OF LSI
LSI(IXA094DR)
The I/O signal of the LSI(IXA094DR) are detailed in the following table.
Pin No.
Signal
I/O
Description
A
B
C
H: GND
L
0.12 sec
2.4 sec
1.2 sec
1.2 sec
20 msec.
H : GND
L (-5V)
1
C1
IN
Terminal not used.
2
VL1
IN
Power source voltage input terminal.
Standard voltage for LCD.
3
AN7
IN
Terminal to change the on timing of the cook relay (RY2).
4-5
AN6-AN5
IN
Heating constant compensation terminal.
6
AN4
OUT
Terminal not used.
7
AN3
IN
Temperature measurement input: OVEN THERMISTOR.
By inputting DC voltage corresponding to the temperature detected by the
thermistor, this input is converted into temperature by the A/D converter built
into the LSI.
8
AN2
IN
Input signal which communicates the door open/close information to LSI.
Door closed; "H" level signal.
Door opened; "L" level signal.
9-10
AN1-AN0
OUT
Terminal not used.
11
P57
OUT
Timing signal output terminal for temperature measurement(OVEN
THERMISTOR).
"H" level (GND) : Thermistor OPEN timing.
"L" level (-5V) : Temperature measuring timing. (Convection cooking)
12
P56
OUT
Signal to sound buzzer.
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.
13
P55
OUT
Timing signal output terminal for temperature measurement(OVEN
THERMISTOR).
"H" level (GND) : Thermistor OPEN timing.
"L" level (-5V) : Temperature measuring timing. (Convection cooking)
14-18
P54-P50
OUT
Terminal not used.
19
P47
IN
Signal coming from touch key.
When any one of G12 line keys on key matrix is touched, a corresponding
signal from P40, P41, P72, P73, P74, P75, P76 and P77 will be input into P47.
When no key is touched, the signal is held at "L" level.
20
P46
IN
Signal similar to P47.
When any one of G11 line keys on key matrix is touched, a corresponding
signal will be input into P46.
21
P45
IN
Signal similar to P47.
When any one of G10 line keys on key matrix is touched, a corresponding
signal will be input into P45.
22
P44
IN
Signal similar to P47.
When any one of G9 line keys on key matrix is touched, a corresponding signal
will be input into P44.
23
INT1
OUT
Terminal not used.
24
INT0
IN
Signal to synchronized LSI with commercial power source
frequency(50Hz).
This is basic timing for time processing
of LSI.
25
P41
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P44 - P47
terminal while one of G8 line key on matrix is touched.
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