Daewoo MCB780W Service Manual page 29

3. When there is no microwave oscillation
1) When touching START pad, oven lamp does not turn on.
Fan motor do not rotate, but cook indicator in display comes on.
* Cause : RELAY 2 does not operate.
- Check method
STATE
RELAY 2 ON
RELAY 2 OFF
2) When touching START pad, oven lamp turns on.
Fan motor and turntable rotate and cook indicator in display comes on.
* Cause : RELAY 1 does not operate.
- Check method
STATE
RELAY 1 ON
RELAY 1 OFF
4. When the door is opened during operation, the count down timer does not stop.
refer to Circuit Diagram (Point 1)
-Check method
STATE
1) DOOR OPEN
2) DOOR CLOSED
CHECK NO
1 Check the stage (ON, OFF) of the door open monitor switch by
resistance measurement.
5. When the digital clock does not operate properly.
refer to Circuit Diagram (Point 5)
POINT
A
* If clock does not keep exact time, you must check resistor R15, 16 zener diode ZD1.
refer to Circuit Diagram (Point 3)
POINT
refer to Circuit Diagram (Point 2)
POINT
POINT
METHOD
WAVE FORM
28
A
-5VDC
GND
A
-5VDC
GND
A
OPEN
CLOSE
T:16.7ms(60Hz)
B
GND
-12VDC
B
GND
-12VDC
B
-5VDC
GND
REMEDY
Replace door open monitor
switch.