KOC-1B0K9A27
- KOC-1B4K9A27 - KOC-1B5K9A27 - Daewoo Microwave Oven – How to troubleshoot – Tests –
Circuit Diagram – Faults and reasons
MEASUREMENT
OF THE MICROWAVE POWER OUTPUT
Microwave
output power can be checked by indirectly measuring the temperature rise of a
certain amount of water exposed to the microwave.
1. A
cylindrical container of borosilicate glass is used for the test. It has a
maximum thickness of 3mm, an external diameter of approximately 190mm and a
height of approximately 90mm. The mass
of the container is determined.
2. At the start of the test, the oven and the empty container are at ambient temperature. Water having an initial temperature of 10ºC ± 1ºC is used for the test. The water temperature is measured immediately before it is poured into the container.
3. A quantity of 1000g 5g of water is added to the container and its actual mass obtained. The container is then immediately placed in the centre of the oven shelf, which is in its lowest normal position. The oven is operated and the time for the water temperature to attain 20ºC ± 2ºC is measured. The oven is then switched off and the final water temperature is measured within 60s.
2. At the start of the test, the oven and the empty container are at ambient temperature. Water having an initial temperature of 10ºC ± 1ºC is used for the test. The water temperature is measured immediately before it is poured into the container.
3. A quantity of 1000g 5g of water is added to the container and its actual mass obtained. The container is then immediately placed in the centre of the oven shelf, which is in its lowest normal position. The oven is operated and the time for the water temperature to attain 20ºC ± 2ºC is measured. The oven is then switched off and the final water temperature is measured within 60s.
NOTE
1 - The water stirred is before its temperature is measured.
NOTE 2 - Stirring and measuring devices are to have a low heat capacity.
4. The microwave power output is calculated from the formula:
NOTE 2 - Stirring and measuring devices are to have a low heat capacity.
4. The microwave power output is calculated from the formula:
[P = 4,187 • mW (T2
-T1) + 0.55 • mC(T2 - T0)/t]
where:
P is the microwave power output, in watts ;
P is the microwave power output, in watts ;
mW
is the mass of the water, in grams ;
mc
is the mass of the container, in grams ;
T0 is ambient temperature, in degrees Celsius ;
T1 is the initial temperature of the water, in degree Celsius ;
T2 is the final temperature of the water, in degrees Celsius ;
t is the heating time, in seconds, excluding the magnetron filament heating-up time.
T0 is ambient temperature, in degrees Celsius ;
T1 is the initial temperature of the water, in degree Celsius ;
T2 is the final temperature of the water, in degrees Celsius ;
t is the heating time, in seconds, excluding the magnetron filament heating-up time.
The
microwave power output is stated in watts, rounded off to the nearest 50W
CAUTION
1. Water load should be measured exactly to 1 liter.
2. Input power voltage should be exactly specified voltage (Refer to SPECIFICATIONS).
3. Ambient temperature should be 20 ± 2°C (68 ± 3.6°F).
1. Water load should be measured exactly to 1 liter.
2. Input power voltage should be exactly specified voltage (Refer to SPECIFICATIONS).
3. Ambient temperature should be 20 ± 2°C (68 ± 3.6°F).
MICROWAVE
RADIATION TEST
Make
sure to check the microwave leakage before and after repair of adjustment.
2. Always start measuring of an unknown field to assure safety for operating personnel from microwave energy.
3. Do not place your hands into any suspected microwave radiation field unless the safe density level is known.
4. Care should be taken not to place the eyes in direct line with the source of microwave energy.
5. Slowly approach the unit under test until the radiometer reads an appreciable microwave leakage from the unit under the test.
2. Always start measuring of an unknown field to assure safety for operating personnel from microwave energy.
3. Do not place your hands into any suspected microwave radiation field unless the safe density level is known.
4. Care should be taken not to place the eyes in direct line with the source of microwave energy.
5. Slowly approach the unit under test until the radiometer reads an appreciable microwave leakage from the unit under the test.
1. Prepare
Microwave Energy Survey Meter, 600cc glass beaker, and glass thermometer 100°C
(212°F).
2. Pour 275cc ± 15cc of tap water initially at 20 ± 5°C (68 ± 9°F) in the 600 cc glass beaker with an inside diameter of approx. 95 mm(3.5 in.).
3. Place it at the center of the tray and set it in a cavity.
4. Close the door and operate the oven.
2. Pour 275cc ± 15cc of tap water initially at 20 ± 5°C (68 ± 9°F) in the 600 cc glass beaker with an inside diameter of approx. 95 mm(3.5 in.).
3. Place it at the center of the tray and set it in a cavity.
4. Close the door and operate the oven.
5. Measure the
leakage by using Microwave Energy Survey Meter with dual ranges, set to 2450MHz.
1) Measured radiation leakage must not exceed the value prescribed below. Leakage for a fully assembled oven with door normally closed must be less than 4mW/Cm2.
2) When measuring the leakage, always use the 5 cm (2 in.) space cone with probe. Hold the probe perpendicular to the cabinet and door. Place the space cone of the probe on the door, cabinet, door seem, door viewing screen, the exhaust air vents and the suction air vents.
1) Measured radiation leakage must not exceed the value prescribed below. Leakage for a fully assembled oven with door normally closed must be less than 4mW/Cm2.
2) When measuring the leakage, always use the 5 cm (2 in.) space cone with probe. Hold the probe perpendicular to the cabinet and door. Place the space cone of the probe on the door, cabinet, door seem, door viewing screen, the exhaust air vents and the suction air vents.
3)
Measuring should be in a counter-clockwise direction at a rate of 1 in./sec. If
the leakage of the cabinet door seem is unknown, move the probe more slowly.
4) When measuring near a corner of the door, keep the probe perpendicular to the areas making sure the probe end at the base of the cone does not get closer than 2 in. from any metal. If it does not, erroneous reading may result.
4) When measuring near a corner of the door, keep the probe perpendicular to the areas making sure the probe end at the base of the cone does not get closer than 2 in. from any metal. If it does not, erroneous reading may result.
Circuit Diagram (Schematic)
Click on the pictures to magnify
COMPONENT
TEST PROCEDURE
==> High voltage is present at the high voltage terminal of the high voltage transformer during any cooking cycle.
==> It is neither necessary nor advisable to attempt measurement of the high voltage.
==> Before touching any oven components or wiring, always unplug the oven from its power source and discharge the capacitor.
==> High voltage is present at the high voltage terminal of the high voltage transformer during any cooking cycle.
==> It is neither necessary nor advisable to attempt measurement of the high voltage.
==> Before touching any oven components or wiring, always unplug the oven from its power source and discharge the capacitor.
High
voltage transformer
1) Remove connections from the transformer terminals and check continuity.
2) Normal readings should be as follows :
Secondary winding ... Approx. 100 Ω
Filament winding ... Approx. 0 Ω
Primary winding ... Approx. 1.2 Ω
1) Remove connections from the transformer terminals and check continuity.
2) Normal readings should be as follows :
Secondary winding ... Approx. 100 Ω
Filament winding ... Approx. 0 Ω
Primary winding ... Approx. 1.2 Ω
High
voltage capacitor
1) Check continuity of capacitor with meter on the highest OHM scale.
2) A normal capacitor will show continuity for a short time, and then indicate 10MΩonce the capacitor charged.
3) A shorted capacitor will show continuous continuity.
4) An open capacitor will show constant 10MΩ .
5) Resistance between each terminal and chassis should be infinite.
1) Check continuity of capacitor with meter on the highest OHM scale.
2) A normal capacitor will show continuity for a short time, and then indicate 10MΩonce the capacitor charged.
3) A shorted capacitor will show continuous continuity.
4) An open capacitor will show constant 10MΩ .
5) Resistance between each terminal and chassis should be infinite.
High
voltage diode
1) Isolate the diode from the circuit by disconnecting the leads.
2) With the ohmmeter set on the highest resistance scale measure the resistance across the diode terminals. Reverse the meter leads and again observe the resistance reading. Meter with 6V, 9V or higher voltage batteries should be used to check the front-back resistance of the diode, otherwise an infinite resistance may be read in both directions. A normal diode's resistance will be infinite in one direction and several hundred kΩ in the other direction.
1) Isolate the diode from the circuit by disconnecting the leads.
2) With the ohmmeter set on the highest resistance scale measure the resistance across the diode terminals. Reverse the meter leads and again observe the resistance reading. Meter with 6V, 9V or higher voltage batteries should be used to check the front-back resistance of the diode, otherwise an infinite resistance may be read in both directions. A normal diode's resistance will be infinite in one direction and several hundred kΩ in the other direction.
Magnetron
For complete magnetron diagnosis, refer to "Measurement of the Microwave Power Output." Continuity checks can only indicate and open filament or a shorted magnetron. To diagnose for an open filament or a shorted magnetron,
1) Isolate magnetron from the circuit by disconnecting the leads.
2) A continuity check across magnetron filament terminals should indicate 0.1 Ω or less.
3) A continuity check between each filament terminal and magnetron case should read open.
For complete magnetron diagnosis, refer to "Measurement of the Microwave Power Output." Continuity checks can only indicate and open filament or a shorted magnetron. To diagnose for an open filament or a shorted magnetron,
1) Isolate magnetron from the circuit by disconnecting the leads.
2) A continuity check across magnetron filament terminals should indicate 0.1 Ω or less.
3) A continuity check between each filament terminal and magnetron case should read open.
Fuse
If the fuse in the primary and monitor switch circuit is blown when the door is opened, check the primary and monitor switch before replacing the blown fuse. In case the fuse is blown by an improper switch operation, replace the defective switch and fuse at the same time. Replace just the fuse if the switches operate normally.
If the fuse in the primary and monitor switch circuit is blown when the door is opened, check the primary and monitor switch before replacing the blown fuse. In case the fuse is blown by an improper switch operation, replace the defective switch and fuse at the same time. Replace just the fuse if the switches operate normally.
Interlock
switches
1) You can test continuity of safety interlock and monitor switch by using ohmmeter.
2) The switch peration is checked by zero/unlimited. The meter should indicate zero resistance.
3) The sequence of check is interlock monitor switch, primary and secondary interlock switches check.
1) You can test continuity of safety interlock and monitor switch by using ohmmeter.
2) The switch peration is checked by zero/unlimited. The meter should indicate zero resistance.
3) The sequence of check is interlock monitor switch, primary and secondary interlock switches check.
CIRCUIT
CHECK PROCEDURE
Low
voltage transformer check
The low voltage transformer is located on the P.C.B.
Measuring condition: Input voltage: 120V / Frequency: 60Hz
The low voltage transformer is located on the P.C.B.
Measuring condition: Input voltage: 120V / Frequency: 60Hz
[1.
Secondary side voltage of the low voltage transformer changes in proportion to
fluctuation of power source voltage.
2. The allowable tolerance of the secondary voltage is within ± 5% of nominal voltage.]
2. The allowable tolerance of the secondary voltage is within ± 5% of nominal voltage.]
Each
measure point must be measured with GND points.
The marks of the above corresponding voltage (+5V, +24V) are written on the PCB.
The marks of the above corresponding voltage (+5V, +24V) are written on the PCB.
Case
of no microwave oscillation
1) When touching M/W button, oven lamp turns on and Fan motor and turntable rotate, and cook indicator in display comes on.
*Cause: RELAY 1 does not operate.
1) When touching M/W button, oven lamp turns on and Fan motor and turntable rotate, and cook indicator in display comes on.
*Cause: RELAY 1 does not operate.
2)
When touching M/W button, oven lamp does not turn on and turntable does not
rotate but cook indicator in display comes on.
*Cause: RELAY 1 does not operate.
*Cause: RELAY 1 does not operate.
3)
When touching M/W button, fan motor does not rotate but turntable rotates, oven
lamp turns on and cook indicator in display comes on.
*Cause: RELAY 5 does not operate.
*Cause: RELAY 5 does not operate.
Case
of no heating of upper grill
When touching GRILL1 & COMBI button, oven lamp turns on and Fan motor and turntable rotate, and cook indicator in display comes on.
*Cause: RELAY 2 does not operate.
When touching GRILL1 & COMBI button, oven lamp turns on and Fan motor and turntable rotate, and cook indicator in display comes on.
*Cause: RELAY 2 does not operate.
Case
of no heating of lower grill
When touching GRILL2 & COMBI button, oven lamp turns on and Fan motor and turntable rotate and cook indicator in display comes on.
*Cause: RELAY 7 does not operate.
When touching GRILL2 & COMBI button, oven lamp turns on and Fan motor and turntable rotate and cook indicator in display comes on.
*Cause: RELAY 7 does not operate.
Case
of no heating of convection grill
When touching CONVECTION button, oven lamp turns on and Fan motor and turntable rotate and cook indicator in display comes on.
*Cause: RELAY 3 does not operate.
When touching CONVECTION button, oven lamp turns on and Fan motor and turntable rotate and cook indicator in display comes on.
*Cause: RELAY 3 does not operate.
Case
of no stopping of the count down timer
When the door is opened during operation, the count down timer does not stop.
When the door is opened during operation, the count down timer does not stop.
[Check
the stage(ON,OFF) of the door open monitor switch by resistance measurement. Replace door open monitor switch if found
faulty.
