Daewoo N230S, Service Manual

Page: 26 / 33

25
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
PRINTED CIRCUIT BOARD
NO CHECK POINT REMARK
1 IC 1 PIN 2, 21, 30, 34 -5 VDC
2 IC 1 PIN 35
3 IC 1 PIN 31 OR 32
NOTE :
Each measure point must be measured with GND point.
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.
0V
-5V
0V
-5V
Terminal Voltage
4-7
LOAD
AC 12.6 V
NO LOAD
AC 14.7 V
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, D12, 13, 14 NO LOAD
T:20ms(50Hz)
T:250ns(4MHz)