NEC MultiSync 20WGX2 Service Manual page 107

1 1 1.4 1.4 Check Check the U the USB IC SB IC
Is 3.3V supplied to I319 Vcc pin Is 3.3V supplied to I319 Vcc pin
3,7,11,15,19,23,27,33,39,45,55? 3,7,11,15,19,23,27,33,39,45,55?
Does X302 oscillate Does X302 oscillate
(24 MHz) ? (24 MHz) ?
Does it have the output of the High Level Does it have the output of the High Level
(more than 4.75V) from I318, I320 (more than 4.75V) from I318, I320
Pin 5 and 8? Pin 5 and 8?
Failure point Failure point
I318, I320 failure I318, I320 failure
OK OK
OK OK
OK OK
Proceed Proceed "9. Check "9. Check the DC/DC
NG NG
converter circuit" section. converter circuit" section.
Does the output of Does the output of
X302 satisfy a threshold X302 satisfy a threshold
NG NG
level ( High:more than level ( High:more than
2.2V,Low:less than 2.2V,Low:less than
0.8V) ? 0.8V) ?
OK OK
Failure point Failure point
I308 failure I308 failure
NG NG Does I318, I320 short ? Does I318, I320 short ?
OK OK
Failure point Failure point
Faulty operation of the over Faulty operation of the over
current protection function. current protection function.
6 - 16 6 - 16
the DC/DC
Failure point Failure point
NG NG
X302 failure X302 failure
Failure point Failure point
NG NG
I318, I320 I318, I320
failure failure