Samsung G-643C User manual

SERVICE MANUAL
SAMASUNG G-643C
MODEL

2. Specifications
2-1 Table of Specifications
Samsung Electronics 2-1
TIMER 99 MINUTES 90 SECONDS
POWER SOURCE 230V 50Hz, AC
POWER CONSUMPTION MICROWAVE : 1,350W
GRILL : 1,000W
OUTPUT POWER FROM 80 TO 800W (10 LEVEL POWER)
(IEC-705 TEST PROCEDURE)
OPERATING FREQUENCY 2,450MHz
MAGNETRON OM75SH(31)
COOLING METHOD COOLING FAN MOTOR
OUTSIDE DIMENSIONS 489(W) x 275(H) x 361(D)
POWER LEVEL
%
10% 80W 4 sec 26 sec
20% 160W 7 sec 23 sec
30% 240W 10 sec 20 sec
40% 320W 13 sec 17 sec
50% 400W 16 sec 14 sec
60% 480W 19 sec 11 sec
70% 560W 22 sec 8 sec
80% 640W 25 sec 5 sec
90% 720W 28 sec 2 sec
100% 800W 30 sec 0 sec
ON TIME OFF TIME
2-2 Comparison Chart
MODEL
FEATURE
MORE/LESS ¡
AUTO COOK/DISH ¡
AUTO DEFROST ¡
TIME COOK ¡
POWER LEVEL ¡
INSTANT COOK ¡
MEMORY ¡
BOOST ¡
CHILD LOCK X
CLOCK ¡
GRILL ¡
COMBI X
G643C
G643C

3. Operating Instructions
3-1 Control Panel
Samsung Electronics 3-1
3-2 Features & External Views
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Door VentilationSlot Heater Light SafetyInterlockHoles
ControlPanel
OpenDoorPushButton
GuideRoller
MetalRack
GlassPlate
DoorLatches
Auto
10min
1min
h
10s.
min
G643C
1 min +
Auto
lbs. oz.
g
kg
489mm
356.5mm
275mm
203mm
361mm
Auto
10min
1min
h
10s.
min
G643C
1 min +
Auto
lbs. oz.
g
kg
Auto
10min
1min
h
10s.
min
G643C
1 min +
Auto
lbs. oz.
g
kg
Instant Cook Button
Auto Cook Button
Memory Button
Kg,g,more and less Button
Auto Defrost Button
Clock Setting Button
Timer Setting Button
MWO/Grill Cycle Button
Start and Boost Button
Stop Button
Grill Button
Power Level Selection Button
Cooking Timer/Standing
Timer Setting Button

4. Disassembly and Reassembly
4-1 Replacement of Magnetron, Motor Assembly and Lamp
Samsung Electronics 4-1
Remove the magnetron including the shield case,
permanent magnet, choke coils and capacitors (all
of which are contained in one assembly).
1. Disconnect all lead wires from the magnetron
and lamp.
2. Remove a screw securing the magnetron
supporter.
3. Remove the magnetron supporter.
4. Remove the air cover.
5. Remove screws securing the magnetron to the
wave guide.
6. Take out the magnetron very carefully.
7. Remove screws from the back panel.
8. Take out the fan motor.
9. Remove the oven lamp by rotating to pull out
from hole of air cover.
NOTE1: When removing the magnetron, make
sure that its antenna does not hit any
adjacent parts, or it may be damaged.
NOTE2: When replacing the magnetron, be sure
to remount the magnetron gasket in
the correct position and make sure the
gasket is in good condition.
1. Discharge the high voltage capacitor.
2. Disconnect all the leads.
3. Remove the mounting bolts.
4. Reconnect the leads correctly and firmly.
4-1 Replacement of High Voltage Transformer
Lamp
Magnetron H. V. Trans
H. V. Capacitor
Screw
Thermo S/W
Fan Motor
H. V. Trans
Screws

4-3 Replacement of Door Assembly
4-3-1 Removal of Door Assembly
4-2 Samsung Electronics
Remove hex bolts securing the upper hinge and
lower hinge. Then remove the door assembly.
Insert flat screwdriver into the gap between Door
"E" and Door "C" to remove Door "C". Be careful
when handling Door "C" because it is fragile.
Following the procedure as shown in the figure,
insert and bend a thin metal plate between Door
"E" and Door "A" until you hear the 'tick' sound.
1. Insertion depth of the thin metal plate should be
0.5mm or less.
Remove pin hinge from Door "E"
Detach spring from Door "E" and key door.
4-3-2 Removal of Door "C"
4-3-3 Removal of Door "E"
Key Door Spring
Door "E"
Disassembly and Reassembly
Upper Hinge
Lower Hinge Screw
Screw
4-3-4 Removal of Key Door & Spring

Samsung Electronics 4-3
1. Disconnect the oven from the power source.
2. Remove the 10A fuse in the fuse holder.
3. When replacing the 10A fuse, be sure to use an exact replacement part. If new 10A fuse blows out again
after replacement, check the primary interlock switch, door sensing switch and interlock monitor switch.
4. When the above three switches operate properly, check if any other part such as the control circuit board,
blower motor or high voltage transformer is defective.
1. Take out the glass tray, guide roller and coupler from
cavity.
2. Turn the oven upside down to replace the drive motor.
3. Remove a screw securing the drive motor cover.
4. Disconnect all the lead wires from the drive motor.
5. Remove screws securing the drive motor to the cavity.
6. Remove the drive motor.
7. When replacing the drive motor, be sure to remount it
in the correct position.
8. Connect all the leads to the drive motor.
9. Screw the deive motor cover to the base plate with a
screw driver.
10. Remount the coupler in the correct position.
1. Take out the outer panel
2. Disconnect the connectors from the heater ceramic
and wire leade.
3. Remove screws securing the bracket upper to the oven
cavity.
4. Remove one screw securing the bracket heater.
4-4 Replacement of Fuse
4-5 Replacement of Drive Motor
4-6 Replacement of Ceramic Heater
Disassembly and Reassembly
Screw
Drive Motor Cover Base Plate
Drive Motor
Bracket Upper
Screw
Screw
Screw
ceramic
Heater
Bracket
Heater
4-3-5 Reassembly Test
After replacement of the defective component parts of the door, reassemble it and follow the instructions below for proper
installation and adjustment so as to prevent an excessive microwave leakage.
1. When mounting the door to the oven, be sure to adjust the door parallel to the bottom line of the oven
face plate by moving the upper hinge and lower hinge in the direction necessary for proper alignment.
2. Adjust so that the door has no play between the inner door surface and oven front surface. If the door
assembly is not mounted properly, microwave energy may leak from the space between the door and
oven.
3. Do the microwave leakage test.

4-7 Replacement of Control Circuit Board
4-7-1 Removal of Ass'y Control Box
4-4 Samsung Electronics
1. Be sure to ground any static electric charge in
your body and never touch the touch control
circuitry.
2. Disconnect the connectors from the control
circuit board.
3. Remove screws securing the control box
assembly.
4. Remove the screw securing the ground tail of
the keyboard.
1. Pull the lever end of the plastic fastener and
remove the Flexible Printed Circuit(FPC) of
membrane panel.
2. Remove screws securing the control circuit
board.
3. Lift up the control circuit board from the Ass'y
control box.
4. When reconnecting the FPC connector, make
sure that the holes on the connector are properly
engaged with the hooks on the Plastic Fastener.
1. Window display should not be disassembled as
its mounting tabs will be broken. If repair work
is difficult, replace with Ass'y control panel.
2. The membrane key board is attached to the
escutcheon base with doublefaced adhesive
tape. Therefore, applying hot air such as using
of hair dryer is recommended for smoother
removal.
3. When installing new membrane key board,
make sure that the surface of escutcheon base is
cleaned sufficiently so that any problems
(shorted contacts or uneven surface) can be
avoided.
4-7-2 Remonal of Ass'y P.C.B
4-7-3 Removal of Window Display & Membrane Panel
Disassembly and Reassembly
Control Box
FPC Connector
Screw
Screw
Membrane
Panel
Window
Display

Samsung Electronics
5. Alignment and Adjustments
5-1 High Voltage Transformer
5-2 Low Voltage Transformer
5-3 Magnetron
5-1
1. Remove connectors from the transformer terminals
and check continuity.
2. Normal resistance readings are as follows:
(Room temperature = 20ûC)
1. Continuity checks can indicate only an open
filament or a shorted magnetron. To diagnose an
open filament or shorted magnetron :
2. Isolate the magnetron from the circuit by
disconnecting its leads.
3. A continuity check across the magnetron filament
terminals should indicate one ohm or less.
4. A continuity check between each filament terminal
and magnetron case should read open.
1. The low voltage transformer is located on the
control circuit board.
2. Remove the low voltage transformer from the
PCB Ass'y and check continuity.
3. Normal resistor reading is shown in the table.
PRECAUTION
1. High voltage is present at the high voltage terminals during any cook cycle.
2. It is neither necessary nor advisable to attempt measurement of the high voltage.
3. Before touching any oven components or wiring, always unplug the oven from its power source and discharge the high voltage
capacitor.
Filament Terminals
Secondary
Terminal
Primary
Terminals
MODEL G643C
Secondary Approx. 130Ω
Filament Approx.0Ω
Primary Approx.1.920Ω
Terminals Resistance
1~2(Input) 1149Ω
4~5(Output 2.9V) 12.26Ω
7~8(Output17V) 2.574Ω
Cooling Fins
Gasket Plate
Magnetron Antenna

Samsung Electronics
5-4 High Voltage Capacitor
5-5 High Voltage Diode
5-6 Main Relay and Power Control Relay
5-7 Adjustment of Primary Switch, Door Sensing Switch and Monitor Switch
5-2
1. Check continuity of the capacitor with the meter set at the highest resistance scale.
2. Once the capacitor is charged, a normal capacitor shows continuity for a short time, and then indicates 9MΩ.
3. A shorted capacitor will show continuous continuity.
4. An open capacitor will show constant 9MΩ.
5. Resistance between each terminal and chassis should read infinite.
1. Isolate the diode from the circuit by disconnecting its leads.
2. With the ohm-meter set at the highest resistance scale, measure across the diode terminals. Reverse the
meter leads and read the resistance. A meter with 6V, 9V or higher voltage batteries should be used to
check the front-to back resistance of the diode (otherwise an infinite resistance may be read in both
directions). The resistance of a normal diode will be infinite in one direction and several hundred KΩin
the other direction.
1. When mounting Primary switch and Interlock
Monitor switch to Latch Body, consult the
figure.
2. No specific adjustment during installation of
Primary switch and Monitor switch to the latch
body is necessary.
3. When mounting the Latch Body to the oven
assembly, adjust the Latch Body by moving it so
that the oven door will not have any play in it.
Check for play in the door by pulling the door
assembly. Make sure that the latch keys move
smoothly after adjustment is completed.
Completely tighten the screws holding the Latch
Body to the oven assembly.
4. Reconnect to Monitor switch and check the
continuity of the monitor circuit and all latch
switches again by following the components test
procedures.
5. Confirm that the gap between the switch
housing and the switch actuator is no more than
0.5mm when door is closed.
1. The relays are located on the PCB Ass'y. Isolate them from the main circuit by disconnecting the leads.
2. Operate the microwave oven with a water load in the oven. Set the power level set to high.
3. Check continuity between terminals of the relays after the start pad is pressed.
Precaution
For continued protection against radiation hazard, replace parts in accordance with the wiring diagram and be sure to use the
correct part number for the following switches: Primary and secondary interlock switches, and the interlock monitor switch
(replace all together). Then follow the adjustment procedures below. After repair and adjustment, be sure to check the continuity
of all interlock switches and the interlock monitor switch.
Alignment and Adjustments
Door Open Door Closed
Primary switch ∞0
Monitor switch (COM-NC) 0 ∞
Monitor switch (COM-NO) ∞0
Door Sensing S/W ∞0
Primary Interlock Switch
Lever Door(B)
Body Latch
Door Sensing
Switch
Interlock Monitor
Switch

Samsung Electronics 5-3
The output power of the magnetron can be measured by performing a water temperature rise test.
Equipment needed :
* Two 1-liter cylindrical borosilicate glass vessel (Outside diameter 190 mm)
* One glass thermometer with mercury column
NOTE: Check line voltage under load. Low voltage will lower the magnetron output. Make all temperature
and time tests with accurate equipment.
1. Fill the one liter glass vessel with water.
2. Stir water in glass vessel with thermometer, and record glass vessel's temperature ("T1", 10±1ûC).
3. After moving the water into another glass vessel, place it in the center of the cooking tray. Set the oven to high
power and operate for 54 seconds exactly. (2 seconds included as a holding time of magnetron oscillation:)
4. When heating is finished, stir the water again with the thermometer and measure the temperature ("T2").
5. Subtract T1 from T2. This will give you the water temperature rise. (∆T)
6. The output power is obtained by the following formula;
* Output (W) = 100 x ∆T
7. Normal temperature rise for this model is 9ûC to 11ûC at 'HIGH'.
NOTE 1: Variations or errors in the test procedure will cause a variance in the temperature rise.
Additional power test should be made if temperature rise is marginal.
NOTE 2: Output power in watts is computed by multiplying the temperature rise (step E) by a factor of 91
times the of centigrade temperature.
The microwave heat distribution can be checked indirectly by measuring the water temperature rise at
certain positions in the oven:
1. Prepare five beakers made of 'Pyrex', having 100 milliliters capacity each.
2. Measure exactly 100milliliters off water load with a measuring cylinder, and pour into each beaker.
3. Measure the temperature of each water load. (Readings shall be taken to the first place of decimals.)
4. Put each beaker in place on the cooking tray as illustrated in figure below. Start heating.
5. After heating for 2 minutes, measure the water temperature in each beaker.
6. Microwave heat distribution rate can be calculated as follows:
Minimum
Temperature Rise
Heat Distribution = X 100(%)
Maximum
Temperature Rise
The result should exceed 65%.
4.187 x 1000 x ∆T
Output Power = 52.3
52.3 : Heating Time (sec)
4.187 : Coefficient for Water
1000 : Water (cc)
∆T : Temperature Rise (T2-T1)
5-8 Output Power of Magnetron
5-9 Microwave Heat Distribution - Heat Evenness
Alignment and Adjustments
D
D
D/4
D/4
D/4
D/4
Cooking Tray
Beaker
CAUTION
MICROWAVE RADIATION
PERSONNEL SHOULD NOT ALLOW EXPOSURE TO MICROWAVE RADIATION FROM MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.