Service manual

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 55, 56 +5 VDC
2 IC 1 PIN 35
3 IC 1 PIN 26 OR 27
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.
+5V
0V
+5V
0V
Terminal Voltage
4-7
LOAD
AC 13.5 V
NO LOAD
AC 32.0 V
NO MEASURE POINT WAVE FORM REMEDY REMARK
1 MP1 DC +5V±0.25V Replace ZD4, D5, EC3, R30 NO LOAD
2 MP2 DC +11.3V±2.0V Replace Q9, R32, ZD5 NO LOAD
3 MP3 DC +11.3V±2.0V Replace EC4, Q10, R34, ZD6 NO LOAD
T:20ms(50Hz)
T:250ns(4MHz)