Daewoo KOR-631Q2A, 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 : 120V, Frequency : 60Hz
2. Voltage check
• Key check point
• Check method
PRINTED CIRCUIT BOARD
NO CHECK POINT REMARK
1 IC 1 PIN 6, 10, 11 -5 VDC
2 IC 1 PIN 22
3 IC 1 PIN 8 OR 9
NOTE :
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 nominal voltage.
Terminal Voltage
6-7
LOAD
AC 25.3 V
NO LOAD
AC 26.9 V
NO MEASURE POINT WAVE FORM REMEDY REMARK
1 MP1 DC -5V±0.25V Replace R36, R37, R39, ZD2, EC1, EC2 NO LOAD
2 MP2 DC -24V±2.0V Replace D11, 12, 13, 14, EC5, R40 NO LOAD
T:16.7ms(60Hz)
T:250ns(4MHz)