Daewoo KOC-870T0S User manual

Service Manual
Microwave Oven
Model: KOC-870T0S
KOC-875T0S
DAEWOO ELECTRON CS CO., LTD.
S/M No. : C870T0S003
✔ Caution
: In this Manual, some parts can be changed for improving, their
performance without notice in the parts list. So, if you need the
latest parts information,please refer to PPL(Parts Price List) in
Service Information Center (http://svc.dwe.co.kr).

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 microwave power for any service test or inspection within the microwave generating com-
partments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, 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
performed on each oven prior to release to the owner.
TABLE OF CONTENTS
PROPER USE AND SERVICE PRECAUTIONS 2
SPECIFICATIONS 3
NAMES AND FUNCTION OF PARTS 4
CONTROL PANEL 5
OPERATION 6
INTERLOCK MECHANISM FUNCTIONS AND ADJUSTMENTS 7
PRECAUTIONS FOR DISASSEMBLY AND REPAIR 9
DISASSEMBLY AND ASSEMBLY 10
TROUBLE SHOOTING GUIDE 18
MEASUREMENT 24
COMPONENT TEST PROCEDURE 26
WIRING DIAGRAM 27
SCHEMATIC DIAGRAM 28
EXPLODED VIEWS AND PARTS LIST 31
PRINTED WIRING BOARD 32
P.C.B. CIRCUIT DIAGRAM 39
P.C.B. LOCATION NO. 40

2
PROPER USE AND SERVICE PRECAUTIONS
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 opened. 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) This microwave oven weight 17.6kg (38.9 lbs.) and must be placed on a horizontal base strong enough to support
this weight.
2) The oven should be placed as far from high temperature source and vapour as possible.
3) The power supply cord is about 1.1m (3.6ft) long. Earthing is required when connecting the power source.
4) Maximum power consumption of this oven is approximately 2.6Kw(230V). It is suggested that the unit is operated on
such power line (about 13 amperes) that can provide more power than this rating.
5) Object must not be placed on the top enclosure so as not to obstruct air flow for ventilation.
The wires in this mains lead coloured in accordance with the following code.
Green-and-yellow : Earth
Blue : Neutral
Brown : Live
As the colours of the wires in the mains lead of this appliance may not correspond with the coloured markings
identifying the terminals in your plug, proceed as follows:
The wire which is coloured green-and-yellow must be connected the the terminal in the plug which is marked with
the letter ‘E’ or by earth symbol or green-and-yellow.
The wire which is coloured blue must be connected to the terminal which is marked with the letter ‘N’ or coloured
black.
The wire which is coloured brown must be connected to the terminal which is marked with the letter ‘L’ or coloured
red.
WARNING : This appliance must be earthed.
NOTE : This oven is designed for counter-top use only.
IMPORTANT

3
MODEL KOC-870T0S KOC-870T5S
POWER SUPPLY 230V ~ , 50Hz 240V~, 50Hz 230V~, 50Hz
MICROWAVE POWER CONSUMPTION 1,550 W 1,550 W 1,550 W
OUTPUT POWER 900 W (IEC 705) 900W(IEC 706) 900 W (IEC 705)
FREQUENCY 2,450 MHZ 2,450MHz 2,450MHz
GRILL POWER CONSUMPTION 1,150 W 1,200 W 1,150 W
CONVECTION POWER CONSUMPTION 1,550 W 1,600 W 1,550 W
AUTO COOK POWER CONSUMPTION 2,600 W 2,650 W 1,950 W
OUTSIDE DIMENSIONS (W X D X H ) 501 X 398 X 320 mm (19.7 X 15.7 X 12.6 in.)
CAVITY DIMENSIONS (W X D X H) 310 X 310 X 229 mm (12.2 X 12.6 X 9.0 in.)
NET WEIGHT 17.6 kg (38.9 Ibs.)
TIMER 60 minutes
SELECT FUNCTION Microwave/Grill /Convection /Combination
MICROWAVE POWER LEVEL 10 stages
* Specifications subject to change without notice.
332
294 320
501
210
402
Grill
M/W
Combi +1 min
Pie Temp +10 sec
GRILL COMBI WEIGHT
DEFROST
TIME
AUTO
COOK PIE TEMP COOK
kg
1. Roast Beef
2. Roast Pork
3. Roast Chicken
4. Fish Fillets
5. Vegetable
Auto Cook
TIME/WEIGHT
Speedy
-
+
Clock
Defrost
M/W
STOP/
CLEAR START
Fig. 1 Front View Fig. 2 Side View
SPECIFICATIONS
EXTERNAL VIEWS

4
3 5 64
2
1 9 8
8
10
7
11
Grill
M/W
Combi +1 min
Pie Temp +10 sec
GRILL COMBI WEIGHT
DEFROST
TIME
AUTO
COOK PIE TEMP COOK
kg
1. Roast Beef
2. Roast Pork
3. Roast Chicken
4. Fish Fillets
5. Vegetable
Auto Cook
TIME/WEIGHT
Speedy
-
+
Clock
Defrost
M/W
STOP/
CLEAR START
1 DOOR SEAL- Door seal maintains the microwave
within the oven cavity and prevents microwave leakage.
2 DOOR HOOK - When door is closed, it will automatically
lock shut. If door is opened while oven is operating,
magnetron tube will immediately stop operating.
3 DOOR SCREEN - Allows viewing of food. Microwave
cannot pass through perforations in screen.
4 GRILL HEATER- Turns on when grill and simulta-
neous cooking is selected.
5 OVEN LAMP- Automatically turns on during oven
operating.
6 SAFETY INTERLOCK SYSTEM
7 CONTROL PANEL
8 TURNTABLE TRAY - Rotates during cooking and
ensure even distribution of Microwaves. It can also be
used as a cooking utensil.
9 OVEN FRONT PLATE
0 ROTATING BASE- This fits over the shaft in the center
of the oven’s cavity floor. This is to remain in the oven for
all cooking. It should only be removed for cleaning.
q UNDER HEATER
NAMES AND FUNCTION OF PARTS

5
CONTROL PANEL
When blinking, the oven is
operating in COMBI cooking. When blinking, the oven is
operating in WEIGHT
DEFROST.
When blinking, the oven is
operating in TIME DEFROST.
When blinking, the oven is
operating in weight input
mode.
Cooking time is increased
by 1 minute.
Cooking time is increased
by 10 seconds.
FUNCTION BUTTON
Used to select desired oven
operation.;Grill, Combi, Pie
Temp, Auto Cook, M/W,
Defrost.
Stop/Clear Button-Used to select
desired oven operation.;Grill, Combi,
Pie Temp, Auto Cook, M/W,Defrost.
Start Button-Used to start the
selectee cycle.
Speedy Cook Button-
Used to set desired time.
(Time increases by 30 seconds
from 30 seconds to 5 minutes.)
Guide Lamp-
When blinking, it informs you to
be ready to operate dial knob.
Dial Knob-
Used to set the cooking time,
time of day and weight input.
When blinking, the oven is
operating in GRILL
When blinking, the onve is
operating in MICROWAVE
COOK
When blinking, the oven is
operating in AUTO COOK.
When blinking, the oven is
operating in PIE COOK.
Microwave Button-Used to
select the variable microwave
power level. If this button is
pressed for more than 1.3
seconds, number is scrolled
up automatically.
Temp Button Used to set
desired temperature. If this
button pressed for more than
1.3 seconds, number is scrolled
up automatically.
Clock Button-Used to set
time.
When blinking, the oven is
operating in CONVECTION
(TEMP COOK)
Grill
M/W
Combi +1 min
Pie Temp +10 sec
GRILL COMBI WEIGHT
DEFROST
TIME
AUTO
COOK PIE TEMP COOK Kg
1. Roast Beef
2. Roast Pork
3. Roast Chicken
4. Fish Fillets
5. Vegetable
Auto Cook
TIME/WEIGHT
Speedy
-
+
Clock
Defrost
M/W
STOP/
CLEAR START

6
TO STOP THE OVEN WHILE THE OVEN IS OPERATING
1. Press (STOP / CLEAR) button.
- The (STOP) indicator starts blinking.
- You can restart the oven by touching (START) button.
- Touch once more to erase all instruction except clock.
2. Open the door
- You can restart the oven by closing the door and touching button.
ERASING INSTRUCTIONS
•Touch (STOP/CLEAR) button to erase all instructions you set previously.
•Opening the oven door during cooking dose not erase cooking instruction.
•If you touch button during operation, the cooking instructions is all erased.
OPERATION
NOTE : Oven stops operating when door open.

7
The door lock mechanism is a device which has been specially designed to completely eliminate microwave radiation when
the door is opened during operation, and thus to perfectly prevent the danger resulting from the leakage of microwave.
(1) Primary interlock switch
When the door is closed, the hook locks the oven door.
If the door is not closed properly, the oven will not operate.
When the door is closed, the hook pushes the lever downward.
The lever press the button of the primary interlock switch to bring it under ‘ON’condition.
INTERLOCK MECHANISM FUNCTIONS AND ADJUSTMENTS
Mounting
screw
Upper Hook
Primary
interlock
switch

8
(2) Monitor interlock switch
When the door is closed, the hook pushes the lever forward, and pushes the Latch Lever downward the lever press the
button of the interlock monitor switch to bring it under ‘OFF’condition. The latch Lever press the button on the secondary
interlock switch to bring it under ‘ON’condition.
- Adjustment
Interlock monitor switch
When the door is closed, the monitor switch should be opened before other switches close.
When the door is opened, the monitor switch should be closed after other switches open.
Adjustment steps :
a) Loosen the two mounting screws.
b) Adjust the interlock switch assembly position.
c) Make sure that the latch lever moves smoothly after adjustment is completed.
d) Completely tighten the two mounting screws.

9
PRECAUTIONS FOR DISASSEMBLY AND REPAIR
- Cautions 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 in servicing the oven can result in an electric 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 war rubber gloves when servicing the high voltage side.
(3)Warning about the electric charge in the high voltage capacitor. When inspecting and repairing the high voltage side,
always short the capacitor terminals and make sure of discharge.
1. Check the earthing.
Do not operate on a 2-wire extension cord.
The microwave oven is designed to be used when earthed.
It is imperative, therefore, to makes sure it is earthed
properly before beginning repair work.
2. Warning about the electric charge
in the high voltage capacitor.
For about 30 seconds after the operation stops, 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 screw driver to discharge.
(4)When the 15Amp fuse(870T5S: 12Amp) is blown out due to the operation of the monitor switch; replace secondary
interlock switch and monitor switch. Refer to 17 page for the necessary adjustment.
(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 repairing the magnetron.
WARNING : When servicing the appliance, need a care of touching or replacing high potential parts because of
electrical shock or exposing microwave. These parts are as follows - H.V. Transformer, magnetron,
H.V. Diode, H.V. Capacitor.

10
1. To remove cabinet. (Refer to Fig. 1)
1) Remove three screws on cabinet back.
2) Push the cabinet backward.
2. To remove guide wind assembly. (Refer to Fig. 2)
1) Release two screws ¤Ł.
2) Remove back-cover ¤Ø.
3) Pull the fan ¤ºto the motor shaft.
4) Release two screws ¤which secure the motor shaded pole ¤Œ.
5) Reverse the above steps for reassembly.
DISASSEMBLY AND ASSEMBLY
Fig. 1
Fig. 2
54 3
21

11
3. To remove H.V. transformer. (Refer to Fig. 3)
1) Remove four screws 1which secure the
H.V. Transformer bracket to the base plate.
2) Remove the H.V. Transformer 2.
High voltage circuit wiring
2
1
H.V. Trans
H.V. Copacitor
Mognetron
H.V.Diode
H.V.Fuse

12
4. To remove magnetron. (Refer to Fig. 4)
1) Remove one screws ¤Łwhich secure the magnetron ¤.
2) Remove the magnetron.
3) Reverse the above steps for reassembly.
CAUTION : Never install the magnetron without the metallic gasket plate which is packed with each magnetron to
prevent microwave leakage. Whenever repair work is carried out on magnetron, check the microwave
leakage. It shall not exceed 4mW/cm
2
for a fully assembled oven with door normally closed.
Wave guide Magnetron antenna
Metallic gasket plate
Fig. 4
12
Magnetron antenna
Metallic
gasket
plate
Cooling fin
<Magnetron>
Filament terminal

13
5. To remove control panel assembly. (Refer to Fig. 5, 6)
(1) Remove a screw holding control panel assembly to the oven
front plate.
At the same time, draw forward the control panel assembly
from oven front plate.
(2) Remove the Dial knob ¤æ
(3) Remove nine screws ¤æ which secure the main and sub
PCB assembly ¤,¤to control panel ¤Ø.
(4) Remove buttons ¤Œ,¤º,¤,¤.
(5) Remove the Window display ¤Ł, and Decorator Panel ¤.
REF NO. PART CODE PART NAME DESCRIPTION Q’TY REMARK
1 3511602500 DECORATOR C-PANEL ABS 1
2 3515501300 WINDOW DISPLAY PMMA 1 SMOG
3 3516716310 CONTROL-PANEL ABS 1
4 3516906000 BUTTON FUNCTION ABS 1
5 3516905900 BUTTON FUNCTION ABS 1 KOR-816
6 3516905800 BUTTON START ABS 1 KOR-816
7 3516906100 BUTTON FUNCTION ABS 1
8 PKBPMSQ200 PCB SUB AS KOC-970T1S 1
9PKMPMSP700 PCB MAIN AS KOC-870T0S 1
KOC-870T0S
PKMPMSP720 KOC-870T5S
KOC-870T5S
10 7121030811 SCREW TAPPING T2S PAN 3X8 MFZN 9
11 3513403810 KNOB VOLUME ABS 1 KOR-816
Fig. 5
Fig. 6
✔ Caution: In this Service Manual, some parts can be changed for improving, their performance without notice in the parts list. So, if you need the
latest parts information, please refer to PPL(Parts Price List) in Service information Center(http://svc.dwe.co.kr)

14
6. To remove door assembly. (Refer to Fig. 7)
1) Remove two screws 1which secure to hinge.
2) Remove door assembly 2.
3) Remove door above for reassembly taking case to
replace fixing glue.
7. To remove door part. (Refer to Fig. 8)
(1) Remove the Gasket door 7.
(2) Remove the Door seal Ass’y 5.
(3) Remove the Hook 8and Spring 9.
(4) Remove the Supporter barri-s *0 3.
(5) Remove the Barrier Screen 2.
(6) Remove the Handle 0from the Frame door 3.
2
1
REF NO. PART CODE PART NAME DESCRIPTION Q’TY REMARK
1 3512203520 FRAME DOOR ABS XR-401 1
2 3517004510 BARRIER-SCREEN*O GLASS 3.2T 1
3 3515305300 SUPPORTER BARRI-S*O PBT 1
4 3515203600 STOPPER HINGE*T AS KOC-970T1S 1
5 3511709000 DOOR SEAL AS KOC-871C0S 1
6 3517004400 BARRIER-SCREEN*I GLASS 3.0T 1
7 3512301300 GASKET DOOR PBT 1
8 3513101300 HOOK POM 1
9 3515101300 SPRING HOOK PW1 1
10 3512601500 HANDLE DOOR ABS XR-401 1
11 7S341W40B1 SCREW TAPPING T2S PAN 4X12 PW SE 2
Fig. 7
Fig. 8
8
9
0
q
1 2 3 4 5 6 7
✔ Caution: In this Service Manual, some parts can be changed for improving, their performance without notice in the parts list. So, if you need the
latest parts information, please refer to PPL(Parts Price List) in Service information Center(http://svc.dwe.co.kr)

15
8. Method to reduce the gap between the door seal and the oven front surface.
(1) To reduce gap located on part ‘A’.
1) Remove the cabinet.
2) Loosen a screw on top door hinge,
then push the door to contact the
door seal to oven front surface.
3) Tighten a screw.
(2) To reduce gap located on part ‘B’.
1) Loosen a screw on bottom hinge, then push the door to contact the door seal to oven front surface.
2) Tighten a screw.
(3) To reduce gap located on part ‘C’.
1) Remove the cabinet.
2) Loosen a screw on interlock switch assembly located bottom of oven body.
3) Draw the interlock switch assembly inward as possible to engage with hook on the door bottom.
4) Tighten a screw.
(4) To reduce gap located on part ‘D’.
1) Remove the cabinet.
2) Loosen a screw on interlock switch assembly located top of oven body.
3) and 4) are same as step (3).
A D
B C
Grill Combi +1 min
Pie Temp +10 sec
1. Roast Beef
2. Roast Pork
3. Roast Chicken
4. Fish Fillets
5. Vegetable
Auto Cook
TIME/WEIGHT
Speedy
-
+
Clock
Defrost
M/W
STOP/
CLEAR START
NOTE : Small gap may be acceptable if the microwave leakage does not exceed 1mW/cm
2
.
NOTE : The door on a microwave oven is designed to act as an electronic seal preventing the leakage of microwave
energy from the oven cavity during the cook cycle. This function does not require that the door be air-tight,
moisture (condensation) - Tight or light-tight. Therefore, the occasional appearance of moisture, light or the
sensing of gentle warm air movement around the oven door is not abnormal and do not of themselves,
indicate a leakage of microwave energy from the oven cavity. If such were the case, your oven could not be
equipped with a vent, the very purpose of which is to exhaust the vapor-laden air from the oven cavity.

16
9. To remove tray motor and under Heater. (Refer to Fig. 9)
1) Cut the tray motor cover parts from the base plate (Refer to Fig. 9).
2) Remove two screws 7which secure the tray motor 6and supporter to tray motor bracket 4.
3) Remove three screws 1and under heater assembly 2in cavity.
1
2
3
45
6
7
CUTTING(5EA)
Grill
M/W
Combi+1min
PieTemp+10sec
GRILLCOMBI
WEIGHT
DEFROST
TIME
AUTO
COOKPIETEMP
COOK
kg
1. Roast Beef
2. Roast Pork
3. Roast Chicken
4. FishFillets
5. Vegetable
Auto Cook
TIME/WEIGHT
Speedy
-
+
Clock
Defrost
M/W
STOP/
CLEARSTART
Fig. 9

17
10. To remove grill heater assembly. (Refer to Fig. 10)
1) Remove the cabinet.
2) Release two screws 1, and remove the Top cover 2.
3) Release a screws 3, and remove Air Guide outlet 4.
4) Release the above steps for reassembly.
Fig. 10
3
4
2
1

18
(TROUBLE 1) Oven does not operate at all ; any inputs can not be accepted.
TROUBLE SHOOTING GUIDE
Condition Check Result Cause Remedy
Fuse blows Check continuity of
interlock monitor switch
with door closed
(COM¡ŒNC)
Check continuity of both
primary and secondary
interlock switch with door
closed
Check continuity of
primary winding of low
voltage transformer
Disconnect high voltage
fuse and operate the unit
Continuity
No
Continuity
Continuity
Continuity
0 Ωor
infinite
Fuse again
blows
Approx.
150~210
(normal)
Replace
Replace
Replace
Replace
(COM¡ŒNC)
Note 1.
Note 1.
(COM¡ŒNC)
Malfunction of
interlock
monitor switch
No
Continuity
Malfunction of
interlock switch
Check continuity of
primary interlock switch
contact with door partially
open until interlock
monitor switch contact
close
(COM ¤QNC close)
Replace
Note 1.
Shorted contacts
of primary interlock
switch.
Defective low
voltage transformer
Defective high
voltage transformer
Following the procedure below to check if the oven is defective or not.
1. Check earthing before trouble checking.
2. Be careful of the high voltage circuit.
3. Discharge the high voltage capacitor.
4. When checking the continuity of the switches, fuse or high voltage transformer, disconnect one lead wire from these parts
and check continuity with the AC plug removed. To do otherwise may result in a false reading or damage to your meter.
NOTE : When electric parts are checked, be sure the power cord is not inserted the wall outlet.
Check wire harness, wiring, and connected of the terminals, and power cord before check the parts listed
below.

19
(TROUBLE 2) Grill Heater (Top heater) does not heat (Food will not become hot).
Condition Check Result Cause Remedy
Replace
Outlet has
proper voltage.
Fuse does not
blow.
Check
continuitymagnetron
No
Continuity
Defective magnetron
Replace
Check continuity of
noise filter board
No
Continuity
Defective line filter
board
Condition Check Result Cause Remedy
Adjust or
replace
Grill heater is
not heated Check continuity of primary interlock
switch
No
Continuity
Malfunction of Primary
Interlock Switch
Adjust or
replace
Check continuity of
secondary interlock
switch
No
Continuity
Malfunction of
secondary interlock
switch
Replace
Check continuity of
heater
No
Continuity
Defective heater
Replace
Check D.C. voltage
being supplied to
RELAY (RY2) coil
0V
Defective touch control
circuit
Replace
Approx.
13VDC
Faulty contacts of
RELAY (RY2) or open
relay coil
Adjust.
No
Continuity
Normal
Open power supply
cord
Adjust.
Check continuity of
power supply cord
Defective touch control
circuit
NOTE1 : All these switches must be replaced at the same time, please refer to page 17 for adjustment instructions