Sharp R-2498G (serv.man5) Service Manual ▷ View online
15
R-2498G
L (min)
Cx
±
20%
Cy
±
20%
0.5mH
0.22
µ
F
4700 pF
MEASURING POINT
INDICATION OF OHMMETER
Between N and L
Open circuit
Between terminal N and WHITW
Short circuit
Between terminal L and BLK
Short circuit
If incorrect readings are absorbed, replace the noise filter.
CARRY OUT 4R CHECKS.
L
N
L
L
F1
Cy
BLK
WHT
Cx
N
CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI etc. Therefore, unlike
conventional microwave ovens, proper maintenance cannot 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 Switch Unit, troubleshooting by unit replacement is described according to the symptoms indicated.
1. Switch Unit
conventional microwave ovens, proper maintenance cannot 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 Switch Unit, troubleshooting by unit replacement is described according to the symptoms indicated.
1. Switch Unit
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the select buttons, a certain button produces no signal at all.
b) When touching the select buttons, sometimes a button produces no signal.
a) When touching the select buttons, a certain button produces no signal at all.
b) When touching the select buttons, sometimes a button produces no signal.
2. Control Unit
The following symptoms may indicate a defective control unit. Replacing the control unit.
2-1 Programming problems.
a) When touching the select buttons, a certain group of buttons do not produce a signal.
2-2 Display problems.
a) For a certain digit, all or some segments do not light up.
b) For a certain digit, brightness is low.
c) Only one indicator does not light.
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.
b) For a certain digit, brightness is low.
c) Only one indicator does not light.
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 problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
b) Cooking is not possible.
Note: When defective components, (the Control Unit or Switch Unit) are replaed, the defective part
or parts must be properly packed for return in the shipping carton. with its cushion material, in
which the new replacement part was shipped to you.
which the new replacement part was shipped to you.
O
SWITCH UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Remove the switch unit from the control panel, referring to control panel removal.
3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector
2. Remove the switch unit from the control panel, referring to control panel removal.
3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector
CN-F as described in the following table by using ohmmeter when the switches are released and
depressed.
depressed.
Switches
Terminals
Released
Depressed
SW1
F1 - F4
O.C.
S.C.
SW2
F1 - F5
O.C.
S.C.
SW3
F2 - F4
O.C.
S.C.
SW4
F2 - F5
O.C.
S.C.
SW5
F3 - F4
O.C.
S.C.
4. If incorrect readings are obtained, replace the defective switch.
5. CARRY OUT 4R CHECKS.
5. CARRY OUT 4R CHECKS.
O.C. : Open Circuit
S.C. : Short Circuit
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
16
R-2498G
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
P
RELAY TEST
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on the
PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given below
for repair.
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 J9 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)
S1
S2
2
3
P
TI
C31
D23
+
–
VRS1
(J9)
(J8)
OL, BM
POWER
7
5
3
1
D21
CN–A
a
c
b
d
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.
Q
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
BOARD(PWB) IS OPEN
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 5 and 7 of the connector (A) on the control
unit with an A.C. voltmeter. The meter should indicate 230-240 volts, if not check control unit circuity.
unit with an A.C. voltmeter. The meter should indicate 230-240 volts, if not check control unit circuity.
RY1, RY2 and RY3 Relay Test
These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
DC. voltage indicated ................................ Defective relay.
DC. voltage not indicated .......................... Check diode which is connected to the relay coil. If diode
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,Blower motor and Stirrer motor
RY2
APPROX. 17.5V D.C.
Power transformer 1
RY3
APPROX. 17.5V D.C.
Power transformer 2
CARRY OUT 4R CHECKS.
17
R-2498G
CONTROL PANEL ASSEMBLY
OUTLINE OF CONTROL PANEL
The control section consists of the following units as shown
in the touch control panel circuit.
in the touch control panel circuit.
(1) Control Unit
(2) Key Unit
(2) Key Unit
The principal functions of these units and the signals com-
municated among them are explained below.
municated among them are explained below.
1. Control Unit
Signal of key touch and oven function control are all
processed by one microcomputer.
processed by one microcomputer.
1) Power Supply Circuit
This circuit changes output voltage at the secondary
side of the low voltage (T1) transformer to volatges
required at each part by full wave rectifying circuit,
constant voltage circuit, etc..
side of the low voltage (T1) transformer to volatges
required at each part by full wave rectifying circuit,
constant voltage circuit, etc..
2) ACL Circuit
This is an Auto-clear Circuit, i.e., a reset circuit, which
enables IC1 to be activated from initial state.
enables IC1 to be activated from initial state.
3) Power SYNC Signal Generating Circuit
This is a circuit for generating power SYNC signal by
virtue of the secondary side output of transformer T1.
This signal is used for a basic frequency to time process-
ing and so on.
virtue of the secondary side output of transformer T1.
This signal is used for a basic frequency to time process-
ing and so on.
4) Clock Circuit
This is a circuit for controlling clock frequency required
for operating IC1.
for operating IC1.
5) IC1 (Main Processor)
This is a one-chip microcomputer, responsible for con-
trolling the entire control unit.
trolling the entire control unit.
6) Display Circuit
This is a circuit for driving display tubes by IC1 output.
7) Switch Input Circuit
This is a circuit for transmitting switch input information
to IC1.
to IC1.
8) Sound-body Driving Circuit
This is a circuit for driving sound body by IC1 output.
9) Relay Driving Circuit
This is a circuit for driving output relay by IC1 output.
10) Stop Switch Circuit
This is a circuit for driving IC1 to detect door opening/
closing.
closing.
11) Exhaust Air Temperature Detecting Circuit
This is a circuit for transmitting output change of thermis-
tor (Exhaust Air Temperature Sensor) to IC1.
tor (Exhaust Air Temperature Sensor) to IC1.
12) High Voltage Monitoring Circuit.
This circuit detects problems in the magnetron / high
voltage circuit by sensing a variation in the current
flowing through the primary winding of the high voltage
transformer.
During heating, the primary current of the high voltage
transformers also flows through the primary winding of
the current transformers CT1 and CT2. This causes a
current to be induced in the secondary windings of CT1/
CT2 and results in an AC voltage which is determined
by R30/R31.
This AC voltage is then half wave rectified by D30/D31
and smoothed (filtered) by C30/C31.
This AC voltage is the input to the AN3 and AN4 ports of
IC1, which determines if there is a magnetron / high
voltage problem.
voltage circuit by sensing a variation in the current
flowing through the primary winding of the high voltage
transformer.
During heating, the primary current of the high voltage
transformers also flows through the primary winding of
the current transformers CT1 and CT2. This causes a
current to be induced in the secondary windings of CT1/
CT2 and results in an AC voltage which is determined
by R30/R31.
This AC voltage is then half wave rectified by D30/D31
and smoothed (filtered) by C30/C31.
This AC voltage is the input to the AN3 and AN4 ports of
IC1, which determines if there is a magnetron / high
voltage problem.
HIGH VOLTAGE TRANSFORMER
HIGH VOLTAGE CIRCUIT
MAIN BODY SIDE
MAIN BODY SIDE
T/C SIDE
CT1 or CT2
RY2 or RY3
R30 or
R31
R31
R34 or
R35
R35
D30 or
D31
D31
R32 or
R33
R33
Vc
C30 or C31
IC1
AN3 or
AN4 PORT
AN3 or
AN4 PORT
D32 or
D33
D33
Figure T-1. High Voltage Monitoring Circuit
13) Magnetron Temperature Detecting Circuit.
This is a circuit for transmitting output change of thermis-
tor (Magnetron Temperature Sensor) to IC1.
tor (Magnetron Temperature Sensor) to IC1.
14) Intake Air Temperature Detecting Circuit.
This is a circuit for transmitting output change of thermis-
tor (Intake Air Sensor) to IC1.
tor (Intake Air Sensor) to IC1.
2. Switch Unit
The switch unit is composed of a matrix circuit in which
when a switch it touched, one of signals P43 - P45
generated by the LSI, is passed through the switch and
returned to the LSI as one of signals P50 - P51.
when a switch it touched, one of signals P43 - P45
generated by the LSI, is passed through the switch and
returned to the LSI as one of signals P50 - P51.
3. 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.
18
R-2498G
1
VCC
IN
Connected to GND.
2
VEE
IN
Anode (segment) of Fluorescent Display light-up voltage: -35V.
Vp voltage of power source circuit input.
Vp voltage of power source circuit input.
3
AVSS
IN
Reference voltage input terminal.
A reference voltage applied to the A/D converter in the LSI. Connected to DC. (-5V)
A reference voltage applied to the A/D converter in the LSI. Connected to DC. (-5V)
4
VREF
IN
Reference voltage input terminal.
A reference voltage applied to the A/D converter in the LSI. Connected to GND.
A reference voltage applied to the A/D converter in the LSI. Connected to GND.
5-6
AN7-AN6
IN
Terminal to switch the specification.
7
AN5
IN
Temperature measurement input: INTAKE 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.
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
AN4
IN
A/D input for troubleshooting Magnetron 1.
9
AN3
IN
A/D input for troubleshooting Magnetron 2.
10
AN2
IN
Temperature measurement input: EXHAUST 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.
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.
11
AN1
IN
Temperature measurement input: MAGNETRON 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.
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.
12
P60
IN
Input signal which communicates the door open/close information to LSI.
Door closed; "H" level signal (0V).
Door opened; "L" level signal (-5.0V).
Door closed; "H" level signal (0V).
Door opened; "L" level signal (-5.0V).
13
P55
OUT
Power supply output at thermistor detecting circuit.
(Output -5V in cooking only, but apply high impedance to others to prevent thermistor
from electrolytic corrosion ocurrence.)
(Output -5V in cooking only, but apply high impedance to others to prevent thermistor
from electrolytic corrosion ocurrence.)
14-16
P54-P52
OUT
Terminal not used.
17
P51
IN
Signal coming from switch unit.
When either one of switches SW2 and SW4 on the switch unit is pressed, a correspond-
ing signal out of P44 and P43 will be input into P51.
When either one of switches SW2 and SW4 on the switch unit is pressed, a correspond-
ing signal out of P44 and P43 will be input into P51.
18
P50
IN
Signal similar to P51.
When either one of switches SW1,SW3 and SW5 on the switch unit is pressed, a
corresponding signal out of P43,P44 and P45 will be input into P50.
When either one of switches SW1,SW3 and SW5 on the switch unit is pressed, a
corresponding signal out of P43,P44 and P45 will be input into P50.
19
P47
OUT
Signal to sound buzzer.
This signal is to control the 2.5kHz
continuous signal.
A: Switch touch sound.
B: Completion sound.
This signal is to control the 2.5kHz
continuous signal.
A: Switch touch sound.
B: Completion sound.
20
P46
OUT
Terminal not used.
21
P45
OUT
Switch strobe signal.
Signal is applied to the switch unit. A pulse signal is input to P50 terminal while switch
SW5 is pressed.
Signal is applied to the switch unit. A pulse signal is input to P50 terminal while switch
SW5 is pressed.
22
P44
OUT
Switch strobe signal.
Signal is applied to the switch unit. A pulse signal is input to P50 or P51 terminal while
switch SW3 or SW4 is pressed.
Signal is applied to the switch unit. A pulse signal is input to P50 or P51 terminal while
switch SW3 or SW4 is pressed.
23
P43
OUT
Switch strobe signal.
Signal is applied to the switch unit. A pulse signal is input to P50 or P51 terminal while
switch SW1 or SW2 is pressed.
Signal is applied to the switch unit. A pulse signal is input to P50 or P51 terminal while
switch SW1 or SW2 is pressed.
24
P42
IN
Signal coming from encoder.
When the encoder is turned, the contacts of encoder make pulse signals. And pulse
signals are input into P42.
When the encoder is turned, the contacts of encoder make pulse signals. And pulse
signals are input into P42.
25
INT1
IN
Signal coming from encoder.
Signal similar to R42. Pulse signals are input into INT1.
Signal similar to R42. Pulse signals are input into INT1.
DESCRIPTION OF LSI
LSI(IZA648DR)
The I/O signal of the LSI(IZA648DR) is detailed in the following table.
The I/O signal of the LSI(IZA648DR) is detailed in the following table.
Pin No.
Signal
I/O
Description
A
B
0.12 sec
1.2 sec
1.2 sec
GND
-5V
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