IBM ThinkVision L170, Service Manual

Page: 32 / 54

IBM L170 Service Manual
32
2.PANEL-POWER CIRCUIT
3.I
NVERTER Control Relative Circuit
check R302 should have response from 0V to 5V
When we switch the power switch from on to off
NG
Check the PPWR panel power relative circuit,
Q301, Q302(pin 5,6,7,8)
In normal operation, when LED =green, R302
should =0 v,
OK,R308 have response
NG, no Voltage
Measured the Q302 pin 5,6,7,8= 5 V?
Check U202 pin 1,2,3,4= 5V
OK
OK
Replace Q302 ( Nmos, SI9933)
Yes
Measured the inveter connector CN401
pin 1 on/off control=5V (on)
pin2 PWM signal control dim 0V-5V
NG
Check the Bklt-On relative circuit, R404, R414, R415,
In normal operation, when LED =green,
R415 Bklt-On should =5 v,
If Bklt-On no-response when the power switch turn on-off,
Replace U203 GM5120/2120
NG, still no screen
Replace Power board to new-one, and
Check the screen is normal ??
OK
NG
Replace Power board
& Re-do white balance