KÜPPERBUSCH MW 800.0 User manual

GB
Microwave
MW 800.0

Service Manual: H4-070-14-01-Z
Responsible: D. Rutz KÜPPERSBUSCH HAUSGERÄTE AG
Tel.: [phone] Kundendienst
Fax: [phone] Postfach 100 132
Date: 07.11.2000 45801 Gelsenkirchen

Service Manual MW 800.0 3
For internal use only
Contents
1. Installation requirements ..............................................................................................5
1.1 General .................................................................................................................5
1.2 Grounding instruction ...........................................................................................5
2. General Function and Leakage Tests ..........................................................................6
2.1 General functional test of the microwave .............................................................6
2.2 Microwave Leakage Test .....................................................................................7
3. Trouble shooting guide .................................................................................................8
3.1 Trouble shooting table ..........................................................................................8
3.2 Interlock switch system ........................................................................................9
4. Major component tests ...............................................................................................10
4.1 Testing the door contact monitor switch .............................................................11
4.2 Testing the safety switch ....................................................................................11
5. Wiring diagram MW 800.0 ........................................................................................... 12

4 Service Manual MW 800.0
For internal use only
General Notice
This service manual provides specific information about the operating priniciple of the microwave
MW 800.0 to the service personnel who already has the required technical knowledge concerning the
repair of microwaves.
This service manual covers all for this type relevant technical data.
The description and operating principle of the components that are already known are not mentioned in
this sevice manual. You find the description of these in the service manuals H4-070-14-01 MW 900,
MWG 1000 and MWGD 900.
Please consult these manuals if necessary.
Technical Data MW 800.0
Outside Dimensions
(L) x (H) x (W) 463 mm x 286 mm x 322 mm
Volume of cavity 18l
Weight approx. 15 kg
Features Individual setting of programme sequence
Electronic clock
Turntable
3 automatic defrost programmes
3 cooking programmes
Electrical connection 230V 50 Hz, einphasig
Microwave output Microwaves: 750W
Total consumption 1.25 kW
Microwave frequence 2450 MHz
Model MW 800.0 (E18EM)

Service Manual MW 800.0 5
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1. Installation requirements
1.1 General
1. The oven should be placed on a flat and stable surface.
2. Place the oven away from high temperature and steam sources.
3. Clearance of at least 5 cm on each side must be provided to allow adequate ventilation.
4. The microwave oven must be plugged directly to a 3-prong wall receptacle which is properly
grounded.
5. The power source must be 230V 50Hz 10A single phase.
1.2 Grounding instruction
IMPORTANT!
Disconnect power before servicing, reconnect all grounding devices.
All mechanical parts of this appliance capable of conducting electricity are grounded. In the event of an
electrical short circuit, grounding reduces the risk of electric shock. This appliance is equipped with a
cord having a grounding wire with a ground plug. The plug must be plugged into an outlet that is properly
installed and grounded.
WARNING!
Improper use of the grounding plug may result in electrical shock.
If grounding wires, screws, straps, clips, nuts or washers used to complete a path to ground are removed
for service, they must be returned to their original positions and properly fastened.
GROUNDING SPECIFICATION
Leakage current: 0.5mA max.
Ground path resistance: 0.1 ohm max.

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2. General Function and Leakage Tests
2.1 General functional test of the microwave
The following is a simple test to check if the appliance is generating microwave energy. This test is not
intended to be an accurate test. An accurate measurement of output power must be performed under
strict control following the IEC standard. In field service, accurate measurement of output power is
usually not required.
HIGH FREQUENCY LOSS
A high frequency loss test must be carried out before and after each repair or any
adjustment work
IMPORTANT!
Measuring the power output
The temperature of 1 l of water increases by 14.3 °C per minute if the power output of the appliance is
1 KW.
The power output is measured as follows:
1. The appliance and the base plate of the oven cavity must be clean.
2. Place a thin-walled glass beaker with an approximate diameter of 10 cm and containing 1 l of water
into the centre of the oven cavity, after having determined the water temperature.
3. Run the appliance for 1 minute (control the time by using a stop-watch).
4. Do not start to measure the time until the transormer starts buzzing.
5. Measure the average temperature increase, i.e. [measured temperature after 1 minute] minus
[initial temperature].
6. Divide the result by 14.3. The calculated value represents the power output in KW.
7. The power output of the appliance should be greater than 900 W - 20% (720 W) during its entire
lifetime.
8. The above measurement should be repeated fairly frequently.
Note:
This measurement just represents a rough guide. It will not be possible to carry it out with
total accuracy, meaning that the power output cannot be determined precicely.

Service Manual MW 800.0 7
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2.2 Microwave Leakage Test
Testing equipment
• 600 cc beaker
• Microwave meter
2.2.1 Testing procedure
1. Place 275 cc of water into the beaker and place it in the center of the oven.
2. Turn on the microwave oven by setting the timer ON at full power.
3. Hold the probe of the microwave meter perpendicular to the surface of the oven and scan it at the
rate of approx. 2.5 cm/sec.
4. Test the following areas for microwave leakage:
• Door and control panel
• All ventilation openings
• All lockseams
• Weld at bottom
• Bottom plate
• Oven foot
5. Maximum allowable leakage is 1mW/cm².
6. Record all data.
2.2.2 Oven leakage repair
If the microwace leakage exceeds 5 mW/cm² the service personnel should tell the owner not to operate
the oven again until the appliance has been repaired. The service personnel should notify the
manufacturer and CDRH (FDA) immediately.
1. If the measured leakage exceeds 1mW/cm2the microwave must be repaired.
2. If there is strong microwave leakage at the control element, the ventilating louvres or at the
underride of the appliance please check, if damaged parts or loose screws are the reason. If this is
the case, replace the defective parts and tighten the screws.
3. If there is strong microwave leakage at the outsides of the door, adjust door hinges and latches.
2.2.3 Open door test
With the oven in operation state, open the oven door and check if the oven is still operating. If so, the
service personnel should tell the owner not to operate the oven again and should notify the manufacturer
and CDRH (FDA) immediately.

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3. Trouble shooting guide
3.1 Trouble shooting table
Problem Points to check
Cavity lamp does not light, but other electrical
components (e.g. turntable) are working. 1. Lamp burnt.
2. Bad contact between lamp and lamp socket.
Cavity lamp does not light, all other electrical
components also do not work. 1. Power outlet has no contact to the socket.
No electric supply.
2. Fuse blown.
3. Faulty contact between fuse and fuse
holder/clip.
4. Loose door hinge, door not set properly,
adjustment of locking not correct; this leads
to blowing of the fuse.
5. Faulty connection UL-switch.
6. Short-circuit in electric circuit. Filament of
lamp blown, short-circuit of high-voltage
capacitor; this leads to blowing of fuse.
7. Faulty contact of contacts or connectors of
control element, or primary or secundary
interlock switch.
8. Defective high-voltage diode .
The microwave seems to function but the food
stays cold. 1. Defective magnetron (defective thread, thread short-circuited to earth, etc).
2. Earth conductor of high-voltage transformer
defective.
3. Filament short-circuited to earth.
4. Damaged filament.
5. Faulty contact at magnetron connectors.
6. Defective control units.
7. Damaged high-voltage diode, a humming
sound occurs.
Microwave runs for a short period of time, but then
stops. 1. Blocked cooling fan.
2. Open cooling fan motor circuit.
3. Defective cooling fan control relay.
Turntable does not turn. 1. Defective turntable motor.
2. Deformed turntable shaft.
Circuit breaker is activated. 1. Strong leakage of electrical components
(mostly motor).

Service Manual MW 800.0 9
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3.2 Interlock switch system
1. The interlock and monitor switches positions are not service adjustable. If the screws on the
hinges of the oven door are loosen, the door may not be in a correct position. In this case, the
interlock switches cannot be operated by the latch pins of the door when the door is shut. To repair
the door, remount the door and fasten the screws on the door hinges.
2. The monitor switch is provided to monitor the operation of the primary interlock switch. If the
primary switch fails to operate when the door is open, the monitor switch will form a short circuit
across the supply and the fuse in the oven will blow. Electric arc may form across the switch
contacts of the primary interlock switch, the secondary switch and the monitor switch. The
switches may then be damaged. If the fuse is blown due to the failure of the primary interlock,
repair the failed mechanical parts and replace all the interlock switches.
IMPORTANT!
After replacement of any part of the interlock and monitor circuit:
1. Check if the microswitches are turned ON and OFF by the latches as specified in the table above.
2. Apply sealant to the screws and nuts of the door hinges.
3. Check microwave leakage.
4. Check if the oven will turn off instantly when the door button is pushed to the position where the
door latches leave the interlock switches.
Oven door status Primary switch Secondary switch Monitor switch
open open open close
close close close open

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4. Major component tests
Testing the high-voltage transformer
Attention!
During cooking the high-voltage terminals of the transformer are under a voltage of 2300 V~.
When testing the transformer, keep your hands and all measuring instruments, etc. away
from these high-voltage terminals.
1. Switch off the appliance and discharge the capacitor with an insulated screwdriver.
2. Disconnect the connection lead of the capacitor from the terminal of the high-voltage transformer.
3. Connect the voltmeter to the filament terminals of the magnetron with a toothed clamp and ensure
that you always keep a good distance from the voltmeter and the wires.
4. Connect the appliance to the mains and und start the cooking process. The voltmeter must
indicate a voltage of 3.3 V~.
Caution:
Switch off the appliance before disconnecting the voltmeter.
If the measuring instrument does not indicate any voltage, you must set the correct value and check
whether a voltage of 220 V ~ (240 V) is applied to the primary winding of the transformer during the
cooking process.
1. Measure the resistance of the winding using an ohm meter
2. Primary winding 3 ohm (approx.)
3. Secondary winding 100 ohm (approx.)
4. Filament winding 0 ohm (approx.)
Anode voltage
For reasons of safety, it is neither advisable nor necessary to measure the anode voltage as the
appliance is under high voltage (approx. 4 KV).

Service Manual MW 800.0 11
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4.1 Testing the door contact monitor switch
1. Switch off the appliance, disconnect one wire at the switch and connect an ohmmeter to the switch
terminals.
2. When the door is open, the reading should indicate a short circuit. When the door is closed the
reading should indicate an infinite resistance.
3. The switch must be exchanged if the short circuit or the infinite resistance become a permanent
condition.
Note
After you have exchanged the monitor switch you must check whether the door is open
when the switch is switched on.
4.2 Testing the safety switch
Disconnect the appliance from the mains, remove the wires of terminal 1 of the switch and connect
an ohmmeter between terminals 1 and 4.
The ohmmeter should indicate a short circuit when the door is closed. When the door is open it should
indicate an infinite resistance.
If the short circuit or the infinite resistance become a permanent condition the switch should be
exchanged.
Note
After a safety switch has been exchanged it must be ensured that the switch is activated
when the door is closed.

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5. Wiring diagram MW 800.0