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Model
R-82FBSTM (serv.man2)
Pages
46
Size
1.57 MB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven
File
r-82fbstm-sm2.pdf
Date

Sharp R-82FBSTM (serv.man2) Service Manual ▷ View online

R-82FBSTM - 16
PROCEDURE
LETTER
COMPONENT TEST
J
BLOWN FUSE 20A
I
NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as
described in the following table.
CARRY OUT 3D CHECKS.
If the fuse 20A is blown, there is a short or ground in electrical parts or wire harness. Check them and
replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION:
Only replace fuse 
with
 the correct value replacement.
K
BLOWN FUSE F8A
CARRY OUT 3D CHECKS.
1. If the fuse F8A  is blown when the door is opened, check the monitored latch switch and monitor
switch.
2. If the fuse F8A is blown by incorrect door switching replace the defective switch(es) and the  fuse
F8A.
3. If the fuse F8A is blown, there could be  a short in the asymmetric rectifier or there is a ground in
the wire harness. A short in the asymmetric rectifier may have occurred due to a short or ground in
H.V. rectifier, magnetron, high voltage transformer or H.V. wire. Check them and replace the
defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION:
Only replace fuse 
F8A
 with the correct value replacement.
L (min)
Cx ± 20%
Cy ± 20%
R1
R2
1.0mH
0.22µF
4700pF
10 MΩ
680kΩ
MEASURING POINTS
INDICATION OF OHMMETER
Between N and L
Approx. 680 kΩ
Between terminal N and WHITE
Short circuit
Between terminal L and RED
Short circuit
If an incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
L
GRILL HEATING ELEMENT (TOP) AND BOTTOM HEATING ELEMENTS TESTBOARD (PWB)
IS OPEN
CARRY OUT 3D CHECKS.
Before carrying out the following tests make sure the heating element is cool completely.
1. Resistance of heating element.
Disconnect the wire leads to the heating element to be tested.  Using ohmmeter with low resistance
range. Check the resistance across the terminals of the heating element as described in the
following table.
F8A
20A
WHT
RED
R1
R2
N
Cx
Cy
L
L
L
Table: Resistance of heating element
Parts name
Resistance
Grill heating element (top)
Approximately 48 Ω
Bottom heating element
Approximately 92 Ω
2. Insulation resistance.
Disconnect the wire leads to the heating element to be tested. Check the insulation resistance
between the element terminal and cavity using a 500V - 100MΩ insulation tester.  The insulation
resistance should be more than 10 MΩ in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heating element is probably
faulty and should be replaced.
CARRY OUT 4R CHECKS.
TEST PROCEDURES
R-82FBSTM - 17
M
CONTROL PANEL ASSEMBLY TEST
The 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 control panel assembly is divided into two units, Control Unit and Jog  switch
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. Jog switch Unit  Note : Check Jog switch unit wire harness connection before replacement.
The following symptoms indicate a defective Jog switch unit. Replace the Jog switch unit.
1-1. Tact switch
a) When touching the buttons, a certain button produces no signal at all.
b) When touching the buttons, sometimes a button produces no signal.
1-2. Potentiometer
a) When rotating the potentiometer, the cooking mode can not be selected.
1-3. Encoder
a) When rotating the encoder, the cooking time or the weight of food can not be entered.
2. Control Panel
The following symptoms indicate a defective control unit. Before replacing the control unit,
perform the Jog switch unit test (Procedure N) to determine if control unit is faulty.
2-1  In connection with buttons
a) When touching the buttons, a certain group of buttons do not produce a signal.
b) When touching the buttons, no buttons 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.
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES
N
KEY AND JOG UNIT TEST
If the display fails to clear when the STOP button is depressed, first verify the cable is making good
contact, verify that the stop switch operates properly; that the contacts are closed when the door is
closed and open when the door is open. If the stop switch is good, disconnect the cable that connects
the Jog switch unit to the control unit and make sure the stop switch is closed (either close the door
or short the stop switch connector). Use the Jog switch unit matrix indicated on the control panel
schematic and place a jumper wire between the pins that correspond to the STOP button making
momentary contact. If the control unit responds by clearing with a beep the Jog switch unit is faulty and
must be replaced. If the control unit does not respond, it is faulty and must be replaced. If a specific
button does not respond, the above method may be used (after clearing the control unit) to determine
if the control unit or Jog switch unit is at fault.
CARRY OUT 4R CHECKS.
J-6
J-3
J-3
J-4
J-7
J-8
J-4
J-7
J-8
J-5
J-2
J-1
J-6
J-5
J-2
J-1
SW11
SW12
SW13
SW9
SW10
SW5
SW4
SW7
SW1
SW2
SW3
STOP
POWER
AUTO
SW8
SW6
HELP
R-82FBSTM - 18
PROCEDURE
LETTER
COMPONENT TEST
P
PROCEDURES TO BE TAKEN WITH THE FOIL PATTERN ON THE PRINTED WIRING
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..
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)
NOTE: *At the time of these repairs, make a visual
inspection of the varistor for burning dam-
age and examine the transformer with tester
for the presence of layer short circuit (check
primary coil resistance).
If any abnormal condition is detected, re-
place the defective parts.
CARRY OUT 4R CHECKS.
CN-A
CN-E
D12
7
(J1)
D13
VRS1
a
c
d
b
TEST PROCEDURES
O
RELAY TEST
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
R-82FBSTM - 19
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.
(1) Jog Switch Unit
(2) Control Unit (The Control unit consists of Power unit
and CPU unit.)
The principal functions of these units and signals commu-
nicated among them are explained below.
Jog Switch Unit
The jog switch unit is composed of a matrix, signals
generated in the LSI are sent to the jog switch unit from
P40, P41, P76 and P77.
When a button is touched, a signal is completed through
the jog switch unit and passed back to the LSI through P50
- P53 to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, reset circuit, buzzer circuit, indicator
circuit, encoder circuit,potentiometer circuit, temperature
measurement circuit and back light circuit.
1) LSI
This LSI controls the temperature measurement sig-
nal, tact switch 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) Reset Circuit
A circuit to generate a signals which resets the LSI to
the initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
audible sounds (tact switch touch sound and comple-
tion sound).
6) Stop Switch
A switch to “tell” the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, top and bottom heating ele-
ment, convection motor, fan motor, turntable motor,
touch control transformer 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.
9) Potentiometer Circuit
The circuit makes setting of the cooking mode by
variable resistance.
10) Back Light Circuit
A circuit to drive the back light (Light emitting diodes
LD1 - LD10).
11) Indicator Circuit
This circuit consists 7-digits, 39-segments and 3-com-
mon electrodes using a Liquid Crystal Display.
12)Temperature Measurement Circuit : (OVEN THER-
MISTOR)
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.
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