REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
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Wednesday 6 February 2019

DAEWOO KOC-1B5K9A27 MICROWAVE OVEN - TESTS – CIRCUIT DIAGRAM – FAULTS AND REASONS – TROUBLESHOOTING

Daewoo KOC-1B5K9A27 Microwave Oven - Tests – Circuit Diagram – Faults and reasons – Troubleshooting

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.
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: 
[P = 4,187 • mW (T2 -T1) + 0.55 • mC(T2 - T0)/t]
where:
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.
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).
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.
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.
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.
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.
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 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
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.
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.
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.
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.
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.
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
[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.]
Each measure point must be measured with GND points.
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.
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.
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.
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.
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.
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.
Case of no stopping of the count down timer
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.