Daewoo KOR-639R0S, Service Manual, Page: 25 / 33

24
PRINTED CIRCUIT BOARD
1. CIRCUIT CHECK PROCEDURE
1. Low voltage transformer check
The low voltage transformer is located on the P.C.B.
Measuring condition: Input voltage: 230V / Frequency: 50Hz
2. Voltage Check
- Key check point
- Check method
NOTE
1. Refer to Circuit Diagram (point 4).
2. Secondary side voltage of the low voltage transformer changes in proportion to fluctuation of power source
voltage.
3. The allowable tolerance of the secondary voltage is within ± 5% of nominal voltage.
NOTE
Each measure point must be measured with GND points.
Terminal Voltage
4-6
LOAD
12.6 V AC
NO LOAD
13.6 V AC
NO MEASURE POINT WAVE FORM REMEDY REMARK
1 MP1 -5V DC Replace VL1, EC1, C1, C6 NO LOAD
2 MP2 -12V DC Replace EC2, D8, D9, D10, C7 NO LOAD
NO CHECK POINT REMARK
1 IC 1 PIN 2, 21, 30, 34 -5VDC
2 IC 1 PIN 35
3 IC 1 PIN 31 OR 32
T : 20 ms(50Hz)
0V
-5V
T
T : 250 ns(4MHz)
0V
-5V
T