Daewoo KOC-9N2T7S, Service Manual, Page: 35 / 45

34
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
NO CHECK POINT REMARK
1
5VDC 5%
IC1 PIN 26, 27(KOC-923T9S/R)
2
IC1 PIN 28 (KOC-923T9S/R)
3 IC1 PIN 8 OR 9
12. PRINTED CIRCUIT BOARD
NOTE
1. Secondary side voltage of the low voltage transformer changes in proportion to fluctuation of power source
voltage.
2. The allowable tolerance of the secondary voltage is within 5% of nominal voltage.
NOTE: Each measure point must be measured with GND points.
Terminal
6-7
8-9
9-10
Voltage(load)
AC 17.0 V
AC 1.3 V
AC 1.3 V
Voltage(no load)
AC 19.9 V
AC 1.6 V
AC 1.6 V
T : 20 ms(50Hz)
5V
0V
T
T : 250 ns(4MHz)
5V
0V
T
NO MEASURE POINT WAVE FORM REMEDY REMARK
1 MP1 DC 5V 5% Replace ZD3, EC1(KOC-9N2T7S/R) NO LOAD
2 MP2 DC 24V 20% Replace D18-D21, EC5(KOC-9N2T7S/R) NO LOAD
Replace D18-D21, EC4(KOC-9N3T7S/R)
Replace ZD2, EC1(KOC-9N3T7S/R)