Daewoo KOT-170U0A User manual

Service Manual
Microwave Oven
Model: KOT-170U0A
KOT-170S0A
KOT-174S0A
KOT-175S0A
DAEWOO ELECT ONICS CO., LTD.
S/M No. : T170U0A002
http : //svc.dwe.co.kr Mar. 2002

1
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
(a)Do not operate or allow the oven to be operated with the door open.
(b)Make the following safety checks on all ovens to be serviced before activating the magnetron or other micro-
wave source, and make repairs as necessary: (1) Interlock operation, (2) Proper door closing, (3) Seal and
sealing surfaces (arcing, wear, and other damage), (4) Damage to or loosening of hinges and latches, (5)
Evidence of dropping or abuse.
(c) Before turning on power to the microwave oven for any service test or inspection within the microwave gen-
erating compartments, check the magnetron, wave guide or transmission line, and cavity for proper align-
ment, integrity, and connections.
(d)Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation
and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual
before the oven is released to the owner.
(e)A microwave leakage check to verify compliance with the Federal performance standard should be per-
formed on each oven prior to release to the owner.
TABLE OF CONTENTS
SAFETY AND PRECAUTIONS...........................................................................................................................................2
SPECIFICATIONS...............................................................................................................................................................3
EXTERNAL VIEW................................................................................................................................................................4
INSTALLATION...................................................................................................................................................................4
OPERATIONS AND FUNCTIONS.......................................................................................................................................4
DISASSEMBLY AND ASSEMBLY......................................................................................................................................5
TROUBLE SHOOTING GUIDE .........................................................................................................................................32
MEASUREMENT AND TEST............................................................................................................................................34
WIRING DIAGRAM............................................................................................................................................................41
PRINTED CIRCUIT BOARD..............................................................................................................................................45
EXPLODED VIEW AND PARTS LIST...............................................................................................................................60

2
SAFETY AND PRECAUTIONS
CAUTION :
This Device is to be Serviced Only by Properly Qualified Service Personnel.
Consult the Service Manual for Proper Service Procedures to Assure Continued Safey Operation and for
Precautions to be Taken to Avoid Possible Exposure to Excessive Microwave Energy.
CAUTION :
Microwave Radiation
Personnel Should Be Exposed to the Microwave Energy Which May Radiat from the Magnetron or Other
Microwave Generating device if it is Improperly Used or Connected. All Input and Output Microwave
Connections, Wave-Guide, Flanges and Gaskets Must be Secure. Never Operate the Device Without a
Microwave Energy Absorbing Load Attached. Never Look Into an Openwaveguide or Antenna While the Device
is Energized.
1. FOR SAFE OPERATION
Damage that allows the microwave energy (that cooks or heats the food) to escape will result in poor cooking and may
cause serious bodily injury to the operator. IF ANY OF THE FOLLOWING CONDITIONS EXIST, OPERATOR MUST
NOT USE THE APPLIANCE.(Only a trained service personnel should make repairs.)
1) A broken door hinge.
2) A broken door viewing screen.
3) A broken front panel, oven cavity.
4) A loosened door lock.
5) A broken door lock.
The door gasket plate and oven cavity surface should be kept clean.
No grease, soil or spatter should be allowed to build up on these surfaces or inside the oven.
DO NOT ATTEMPT TO OPERATE THIS APPLIANCE WITH THE DOOR OPEN. The microwave oven has concealed
switches to make sure the power is turned off when the door is opende. Do not attempt to defeat them. DO NOT
ATTEMPT TO SERVICE THIS APPLIANCE UNTIL YOU HAVE READ THIS SERVICE MANUAL.
2. FOR SAFE SERVICE PROCEDURES.
1) If the oven is operative prior to servicing, a microwave emission check should be performed prior to servicing the
oven.
2) If any certified oven unit is found to servicing, a microwave emission check should be performed prior to servicing the
oven.
(a) inform the manufacturer, importer or assembler,
(b) repair the unit at no cost to the owner,
(c) attempt to ascertain the cause of the excessive leakage,
(d) tell the owner of the unit not to use the unit until the oven has been brought into compliance.
3) If the oven operates with the door open, the service person should tell the user not to operate the oven and contact
the manufacturer and CDRH immediately.

3
Model KOT-170U, KOT-170S, KOT-174S, KOT-175S
Power Supply 120V ~ 60 Hz
Rated Current 15A (microwave oven only).
Power Consumption 1700W, Max.
Microwave Output Power (IEC 705) 1100W
Frequency 2450 MHz ±50 MHz
Outside Dimensions (WxHxD) 760x427x381 mm
Cavity Dimensions (WxHxD) 506x256.5x348 mm
Net Weight 24.5Kg
Timer Digital, 99 min 99sec
Power Selections 10 Levels
Cavity Volume 1.7 ft3
Magnetron cooling Forced air
Microwave Distribution turntable
Rectification voltage doubler, half-wave.
Door Sealing Choke System
Safety Device Cavity Thermostat open : 212/100, reset : 32/0
Bottom Thermostat open : 194/90, reset : 32/0
Hood Thermostat open : 104/40, reset : 132.8/56
Line Fuse 20 A
Door Interlock Switches Primary Interlock Switch.
Secondary Interlock Switch.
Interlock Monitor.
Magnetron type 2M218HK
High Voltage Capacitor 0.98 2.1KV AC
High Voltage Diode 350 mA, 9.0 KV
Cook-top Lamp 125V, 30W
Cavity Lamp 125V, 30W
Tray Glass
* SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.
SPECIFICATIONS

4
EXTERNAL VIEW
; REFER TO THE INSTALLATION GUIDE
INSTALLATION
; REFER TO THE INSTALLATION GUIDE
OPERATIONS AND FUNCTIONS
; REFER TO THE INSTALLATION GUIDE

5
DISASSEMBLY AND ASSEMBLY
Caution to be observed when trouble shooting
Unlike many other appliances, the microwave oven is high-voltage, high-current equipment.
It is completely safe during normal operation. However, carelessness is servicing the oven can result in an electronic shock
or possible danger from a short circuit. You are asked to observe the following precautions carefully.
1. Always remove the power plug from the outlet before servicing.
2. Use an insulated screwdriver and wear rubber gloves when servicing the high voltage side.
3. Discharge the high voltage capacitor before touching any oven components or wiring.
1) Check the grounding.
Do not operate on a two-wire extension cord.
It is imperative, therefore, make sure it is grounded properly before
beginning repair work.
2) Warning about the electric charge in the higi voltage capacitor.
for about 30 seconds after the operation has stopped an electric
charge remains in the high voltage capacitor.
When replacing or checking parts, short between oven chassis
and the negative high terminal of the high voltage capacitor by
using a properly insulated screwdrive to discharge.
4. When the 20A fuse is blown due to the operation for the monitor
switch; replace primary interlock switch, secondary interlock switch
and interlock monitor switch.
5. After repair or replacement of parts, make sure that the screws are
properly tightened, and all electrical connections are tightened.
6. Do not operate without cabinet.
CAUTION :
Service personnel should remove their watches whenever working close to or replacing the magnetron.
CAUTION :
When servicing the appliance, take a care when touching or replacing high potential parts because of electrical
shock or exposing microwave. These parts are as follows - HV Transformer, Magnetron, HV Capacitor, HV
Diode.

6
1. GENERAL
-REMOVING / REINSTALLING
-CABINET
CABINET REMOVAL
Refer to FIG. 1 for the following steps:
1. Remove the microwave oven from its mounting location and set it on a protected (padded) work surface.
2. Remove the two screws from the top of the microwave oven that secure the vent grille to the oven, and pull the top of
the vent grille out so the tabs are from their slots, and remove it.
3. Remove 1 screw from the vent motor cover.
4. Remove the remaining 6 screws from the top side and rear of the cabinet. Slide the cabinet back and unhook it from
the side tabs, then slide the power cord into the cabinet, and lift the cabinet off the oven.
Proceed to the section for the component you wish to service.
CABINET INSTALLATION
Refer to FIG. 1 for the following steps:
1. Position the cabinet over the top of the microwave oven and slide the power cord all the way through the top opening.
2. Slide the cabinet forward so that the tabs along the sides of the microwave fit into the corresponding slots in the cabi-
net and tighten the screws.
3. Install the vent grille on the oven with the two screws.
4. Install the oven in it’s mounting location.
WARNING :
Personal Injury Hazard
Disconnect from the electrical supply before servicing the unit. Failure to do so could result in electrical shock or
other personal injury.
CAUTION :
Personal Injury Hazard
Because of the weight and size of the microwave oven, two people are required to safely move and install it.
Failure to do so could result in personal injury.

7
FIG. 1

8
2.THE OPERATING CONTROL SYSTEMS
-REPLACING THE CONTROL CIRCUIT BOARD
1. Remove the two screws from the top of the microwave oven for the vent grille and remove the grille(See FIG. 1).
Refer to FIG. 2, FIG. 2-1 for the following steps:
2. Remove the screw from the front of the microwave oven for wire protector and remove the wire protector.
3. Remove the screw from the top center tab of the control panel.
4. From the top and back of the control panel, lift the top locking tab and pull the top of the panel out slightly, then lift the
bottom tabs of the panel out of the slots and pull it forward.
WARNING :
This Device is to be Serviced Only by Properly Qualified Service Personnel.
Consult the Service Manual for Proper Service Procedures to Assure Continued Safety Operation and for
Precautions to be Taken to Avoid Possible Exposure to Excessive Microwave Energy.
FIG. 2

9
4. Unplug the following connectors from the control circuit board:
a) 2-Pin connector at CN2.
b) 2-Pin connector on relay RY1.
c) 3-Pin connector at CN5.
d) 6-Pin connector at CN4.
e) 6-Pin connector at CN3 (Only sensor type model).
f) Lift the end of the locking arm on the ribbon cable at CN1, then lift the ribbon cable out of the socket.
5. Remove 4 screws from the control circuit board and lift the board off the mounting bracket.
6. Clean the surface of the new display and the inside of the control panel window with a soft, damp cloth to remove any
dirt, smudges, or lint.
7. Mount the new control circuit board to the mounting bracket with 4 screws.
8. Plug the following connectors over their control circuit board plugs so that they lock into place:
a) 2-Pin connector at CN2.
b) 2-Pin connectors on relay RY1.
c) 3-Pin connector at CN5.
d) 6-Pin connector at CN4.
e) 6-Pin connector at CN3 (Only sensor type model).
f) Insert the end of the ribbon cable into the narrow slot of connector CN1 as far as it will go(See FIG. 2-2).
Lower the locking arm so that the two small tabs fit into the cutouts of the ribbon cable, then press down so that it
locks into place.
9. Mount the control panel to the oven and wire protector with mounting screws.
10. Mount the vent grille to the microwave oven and check out the operation.
FIG. 2-1 FIG. 2-2