DAEWOO ELECTRONICS KOR-637V, Service Manual, Page: 28 / 36

27
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 : 120V / Frequency : 60Hz
2. Voltage Check
- Key check point
- Check method
Terminal Voltage LOAD NO LOAD
4 - 7 AC 12.6 AC 14.7V
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
NO MEASURE POINT WAVE FORM REMEDY REMARK
1 MP1 DC - 5V 0.25V Replace VL1, EC1 NO LOAD
2 MP2 DC - 12V 2.0V Replace EC2, D10,11,12 NO LOAD
Each measure point must be measured with GND points.
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 normal voltage.
NOTE
+_
T : 16.6ms(60Hz)
T : 250 ns(4MHz)