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Model
R-8000GK
Pages
44
Size
1.16 MB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven
File
r-8000gk.pdf
Date

Sharp R-8000GK Service Manual ▷ View online

R-8000GK
6
FUNCTION OF IMPORTANT COMPONENTS
Monitor switch
Latch hook left
3rd. latch 
switch
Latch 
head
Secondary
interlock switch
(Monitored latch switch)
Door
sensing switch
(Primary interlock
  relay control switch)
Latch hook right
Latch 
head
FAN MOTOR OPERATION
After cooking is completed, the fan motors will continue for 1
minute. At the end of the cooking cycle, if the cavity air temperature
is above 111˚C, the circuit to RY5 will be maintained (by the
thermistor circuit) to continue operation of the cooling fan motor
until the temperature drops below 90˚C, at which time the relay will
be de-energized, turning off the fan motor.
DOOR OPEN MECHANISM
The door is opened by pulling the door handle down and forward,
referring to the figure D-1. When the door handle is pulled down,
the latch heads are moved upward. And then when the door
handle is pulled forward, the latch heads are released from the
latch hooks right and left. Now, the door will open.
Figure D-1. Door Open Mechanism
DOOR SENSING SWITCH, SECONDARY INTER-
LOCK SWITCH AND 3RD. LATCH SWITCH
1. When the oven door is closed, the contacts (COM-NO) must
be closed.
2. When the oven door is opened, the contacts (COM-NO) must
be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC) must
be opened.
2. When the oven door is opened, the contacts (COM-NC) must
be closed.
3. If the oven door is opened and the contacts (COM-NO) of the
secondary interlock switch and the relay RY2 fail to open, the
fuse F10A blows simultaneously with closing the contacts
(COM-NC) of the monitor switch .
CAUTION: BEFORE REPLACING A FUSE TEST THE SEC-
ONDARY INTERLOCK SWITCH, RELAY RY2 AND
MONITOR SWITCH   FOR PROPER OPERA-
TION. (REFER TO CHAPTER "TEST PROCE-
DURE".)
FUSE F10A
1. The fuse F10A blows when the contacts (COM-NO) of the
secondary interlock switch and relay RY2 remain closed with
the oven door open and when the monitor switch   closes.
2. If the wire harness or electrical components are short-
circuited, the fuse F10A blows to prevent an electric shock of
fire hazard.
HIGH VOLTAGE FUSE
The high voltage fuse blows when the high voltage rectifier or the
magnetron is shorted.
NOISE FILTER
The noise filter prevents the radio frequency interference that
might flow back in the power circuit.
THERMISTOR
The thermistor is a negative temperature coefficient type. The
temperature in the oven cavity is detected through the resistance
of the thermistor, and then the control unit causes the heater relay
to operate, thus the current to the heating elements is turned ON/
OFF. If the convection cooking or some cooking modes which use
the top / side heating elements is started and the oven temperature
does not rise above 37.8˚C, the control unit will stop the oven after
10 minutes. In this case, the thermistor may be opened.
MAGNETRON TEMPERATURE FUSE
The temperature fuse located on the waveguide flange is designed
to prevent damage to the magnetron if an over heated condition
develops in the magnetron due to cooling fan failure, obstructed air
guide, dirty or blocked air intake, etc. Under normal operation, the
temperature fuse remains closed. However, when abnormally
high temperatures are reached within the magnetron, the tempera-
ture fuse will open at 150˚C causing the oven to shut down.
HEATER TEMPERATURE FUSE
The temperature fuse located on the chassis support left is
designed to prevent damage to the chassis support left if an over
heated condition develops in the top and /or side heating
element unit
s due to convection fan failure, thermistor failure,
obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the temperature fuse remains closed.
However, when abnormally high temperature are reached within
the top and /or side heating element unit
s, the temperature fuse
will open at 150˚C causing the oven to shut down.
TOP HEATER THERMAL CUT-OUT
The thermal cut-out located on the thermal cover upper is
designed to prevent damage to the top heating element unit if an
over heated condition develops in the top heating element unit
due to convection fan failure, thermistor failure, obstructed air
ducts, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains closed.
However, when abnormally high temperature are reached within
the top heating element unit, the thermal cut-out will open at
170˚C causing the oven to shut down. When the thermal cut-out
has cooled, the thermal cut-out closes at 155˚C.
SIDE HEATER THERMAL CUT-OUT
The thermal cut-out located on the thermal cover left is designed
to prevent damage to the side heating element unit if an over
heated condition develops in the side heating element unit due
to convection fan failure, thermistor failure, obstructed air ducts,
dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains closed.
However, when abnormally high temperature are reached within
the side heating element unit, the thermal cut-out will open at
150˚C causing the oven to shut down. When the thermal cut-out
has cooled, the thermal cut-out closes at 130˚C.
TOP HEATING ELEMENT
The top heating element is located at the top of the oven cavity.
R-8000GK
7
It is intended to heat air driven by the convection fan. The heated
air is kept in the oven and force-circulated and reheated by the
top heating element.
SIDE HEATING ELEMENT
The side heating element is located at the left side of the oven
cavity. It is intended to heat air driven by the convection fan. The
heated air is kept in the oven and force-circulated and reheated
by the top heating element.
TURNTABLE MOTOR
The turntable motor rotates the turntable located in the bottom of
the oven cavity, so that the food on the turntable is cooked evenly
during cooking. The turntable may turn in either direction.
FAN MOTOR (MAGNETRON SIDE)
The fan motor drives a blade which draws external cool air. This
cool air is directed through the air vents surrounding the magn-
etron and cools the magnetron. This air is channelled through the
oven cavity to remove steam and vapours given off from the
heating foods. It is then exhausted through the exhausting air
vents at the oven cavity.
FAN MOTOR (HIGH VOLTAGE TRANSFORMER
SIDE)
The fan motor drives a blade which draws external cool air. This
cool air is directed through the air vents surrounding the power
transformer and cools the power transformer. This air is chan-
nelled through the oven cavity to remove steam and vapours
given off from the heating foods. It is then exhausted through the
exhausting air vents at the oven cavity.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where food is
not directly heated by the heating element, but is heated by forced
circulation of the hot air produced by the heating elements. The air
heated by the heating elements is circulated through the convec-
tion passage provided on the outer casing of the oven cavity by
means of the convection fan which is driven by the jet motor. It then
enters the inside of the oven through the vent holes provided on the
top and left sides of the oven. Next, the hot air heats the food on the
turntable and leaves the oven cavity through the vent in the centre
of the oven cavity back side wall. Without leaving the oven, this hot
air is reheated by the heating elements, passes through the
convection passage and enters the inside of the oven cavity again,
in a continuing cycle. In this way, the hot air circulates inside the
oven cavity to raise its temperature and, at the same time, comes
into contact with the food being cooked. When the temperature
inside the oven cavity reaches the selected temperature, the
heating elements are de-energized. When the temperature inside
the oven cavity drops below the selected temperature, the heating
elements are energized again. In this way, the inside of the oven
cavity is maintained at approximately the selected temperature.
When the convection time reaches 0, the heating elements are de-
energized and the convection fan stops operating and the oven
shuts off.
Flow of hot air:
The rotation direction of the jet motor is controlled by relay RY6.
When the convection fan rotates clockwise, the hot air from the
oven cavity left side wall blows stronger than one from the oven
cavity top wall. ( This mode is called “Convection mode”.) When
the convection fan rotates counterclockwise, the hot air from the
oven cavity top wall blows stronger than one from the oven cavity
left side wall. (This mode is called “JET mode”.)
Figure D-2. Rotation direction of convection fan
Figure D-3. Flow of hot air
Side heating
element unit
Top heating
element unit
Convection 
fan
Convection mode
JET 
mode
FRONT VIEW
Hot air
Hot air
Hot air
Convection
fan
Hot air
Oven cavity left side
Oven cavity   
top wall
Side heating
element unit
Side heating
element unit
Top heating element unit Top heating element unit
Turntable
Convection Mode
JET Mode
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing the checks.
Many of the possible causes of trouble will require that a
specific test be performed. These tests are given a proce-
dure letter which will be found in the "Test Procedure
"section.
IMPORTANT:
If the oven becomes inoperative because of a
blown fuse F10A in the secondary interlock
swith - monitor switch - primary interlock relay
RY2 circuit, check the monitor switch, relay
(RY1), primary interlock relay (RY2) and sec-
ondary interlock switch before replacing the
fuse F10A.
R-8000GK
8
RE: Replace / CK: Check
Home fuse blows when power cord is plugged into wall receptacle.
Fuse 20A
 blows when power cord is plugged into wall receptacle.
  
  
  
  
  
 does not appear in display when power cord is first plugged into wall 
receptacle.
Fuse F10A
 blows when the door is Opened.
Oven lamp does not light with door opened. 
High voltage transformer
, heating elements, turntable motor and oven lamp 
do not operate.
Oven lamp lights, but turntable motor does not operate.
T
urntable motor operates normally but cooling fan motor does not operate.
Oven does not go into a cook cycle, when ST
AR
T
 key is touched.
Low or no power is produced during microwave cooking (The food is heat-
ed incompletely or not heated at all)
Extremely uneven heating is produced in oven load (food).
Function of variable cooking does not operate properly except 100% power
.
Heating elements do not heat.
T
emperature in the oven cavity is lower or higher than preset.
Jet motor does not operate at all or properly
.
Oven operates for 10 minutes then shuts down, and "EE-6" appears. 
(THERMIST
OR F
AILURE)
"EE-10" appears. (MEMOR
Y
 F
AILURE)
"EE-9" appears. (MAXIMUM 
TIME EXCEEDED)
"CK-1" appears. (T
otal operation time (hours) of magnetron exceeds 1250 
hours.)
"CK-2" appears. (T
otal operation time (hours) of top heating element ex-
ceeds 4000 hours.)
"CK-3" appears. (T
otal operation time (hours) of side heating element ex-
ceeds 4000 hours.)
MAGNETRON
HIGH VOLT
AGE TRANSFORMER
H.V. RECTIFIER 
ASSEMBLY
HIGH VOLT
AGE CAPACIT
OR
SECONDARY
 INTERLOCK SWITCH
3RD. LATCH SWITCH
DOOR SENSING SWITCH
MONITOR SWITCH
HIGH VOLT
AGE FUSE
FUSE 20A
MAGNETRON TEMPERATURE 
FUSE
THERMAL CUT
-OUT (T
OP) 
TOP 
HEATING ELEMENT
THERMISTOR
NOISE FILTER
TOUCH CONTROL
 PANEL
TACT
 SWITCH
RELAY
 RY
-1
RELAY
 RY
-2
RELAY
 RY
-3
RELAY
 RY
-5
RELAY
 RY
-6
FUSE1 ON PWB.
SOLID-STA
TE RELAY
 (TOP)
SOLID-STA
TE RELAY
 (SIDE)
OVEN LAMP
FAN MOT
OR (MAGNETRON)
TURNTABLE MOT
OR
JET MOT
OR
LOOSE WIRING
SHORTED IN POWER CORD  
NO POWER A
T OUTLET
 
LOW VOLT
AGE
THERMAL CUT
 OUT (SIDE)
SIDE HEATING ELEMENT
FAN MOT
OR (H.V. TRANSFORMER)
T/C TRANSFORMER
FUSE F10A
JET MOT
OR CAPACIT
OR
WRONG OPERATION
MISADUSTMENT SWITCH
HEATER TEMPERATURE 
FUSE
TEST
 PROCEDURE
PROBLEM
POSSIBLE CASE 
AND DEFECTIVE P
A
R
T
S
CONDITION
OFF CONDITION
COOKING CONDITION
MICROW
A
VE COOKING
ERROR MODE
EXCEPT
 FOR MICROW
A
V
E
COOKING
AB
C
D
EE
E
F
H
J
K
M
O
G
U
V
W
W
W
W
W
E
YX
X
RE
T
T
RE
P
RE
CK
CK
CK
CK
CK
RL
N
Y
I
Q
R-8000GK
9
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL WHILE
THE OVEN IS IN OPERATION.
1.
CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
3. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check across
the magnetron filament leads should indicate less than 1 ohm.
4. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads and
chassis ground. This test should indicate an infinite resistance. If there is little or no resistance the magnetron
is grounded and must be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet) and the back plate.
7. Reconnect the power supply cord after the outer case and back plate are installed.
8. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer
case fitted).
The power output of this oven is rated using the method specified by  IEC 60705. Full details of how to curry out
this procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).
The IEC60705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.
NOTE: The following test method gives an indication of the output power only, it cannot be used to
establish the actual/rated output power. If the true output power is required, then the IEC60705
test method must be used.
Alternative simplified method:
1. Place 2  litres of cold water (between 12
°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in 
°C. Note temperature as T1.
3. Place the container in the microwave and heat the water for 1 minute and 33 seconds on full power.
NOTE: The operation time of microwave oven includes "3" sec. (3 sec. is magnetron filament heat-up
time.)
4. When the 1 minute and 33 seconds is completed, remove the  container and stir the water. Note the water
temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 90.
NOTE: The result from this test should be within the allowance of 2000cc alternative method.
(
±
10%).
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following the
procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The maximum
leakage permitted in BS EN 60335-2-25 is 50W/m
(equivalent to 5W/m
2
), however it is not normal to detect any
significant leakage, therefore, any leakage which is detected should be investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical Laboratories are
used.
Suitable leakage detectors:
CELTEC A100
APOLLO X1
A
MAGNETRON ASSEMBLY TEST
B
HIGH VOLTAGE  TRANSFORMER TEST
WARNING:
High voltage and large currents are present at the secondary winding and filament
winding of the high voltage transformer. It is very dangerous to work near this part
when the oven is on. NEVER make any voltage measurements of the high-voltage
circuits, including the magnetron filament.
1.
CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to “BACK PLATE REMOVAL”.
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