Switching Power Circuit Failure - NEC MultiSync LCD1920NX User And Service Manual

5. Switching power circuit failure

Is +12V power source available?
(IC18 pin7, 8)
YES
Is +5Vx ok? (This is all TTL IC
power source)
Make sure that the voltage of
between IC22 pins 7, 8 and GND
approximately 5V.
YES
Is VLCD approximately 5V?(This
is panel power source)
1Make sure that the voltage of
between IC22 pin 5 and pin6 to
GND approximate 5V.
Failed
Check power of IC18 Pin 5 and
Pin 6 is 5V. (This is ADC, Scalar,
LVDS power source)
YES
Next page
1) Make sure that the voltage of between IC18 pin1
and GND approximate +5V.
2) Make sure that the voltage of between IC22 pin5
and GND approximate +5V
3) Make sure that the voltage of between IC22 pin7
and GND approximate +5V.
4) Make sure that the voltage of between IC18 pin5
and GND approximate +5V.
NO
1) Check Adapter.
2) Check F1 (fuse).
3) Check JP01.
NO
NO
1) Check IC20 Pi 7 approximately +5.1V. (ZD04)
2) Check IC21 and IC22 if broken.
3) Check D19, L33, IC12, IC20 if any one break.
NO
1) Check IC20 Pin 5 approximate +5V.
2) Check IC19 and IC22 if broken.
3) Check D20, L34, IC12, IC20 if any one is broken?
NO
1) Check IC25 Pin 3 (CPU) if Low-level.
2) Check IC18 ok?
6-10
Failure point
Is IC22 Pin 1 +5V?
YES
Check over voltage protection circuit
work? (IC20 pin14 High level)
Failure point
Is IC22 Pin 3 about +5V?
YES
Check over voltage protection circuit
work? (IC20 Pin13 High level)
Failure point
Failure point
Failure point
Failure point