AOC LM520i, Service Manual

Page: 16 / 40

16
PANEL-POWER CIRCUIT
I
NVERTER Control Relative Circuit
SCILLATOR BLOCK
U200-DATA OUTPUT
OK,R225 have
check R824 should have response from 14V t
0V
When we switch the power switch from on t
Check the PPWR panel power relative circuit,
R223、Q200、Q201(pin2)
In normal operation, when LED =green, R223
should =0 v,
If PPWR no-response when the power switch
Turn on and turn off, replace the U501-GMZAN1
NG
Measured the Q201 pin 2= 3.3 V?
Replace Q201 ( Nmos)
NG, no Voltage
OK,
Replace INVERTER-module
& Re-do white balance
Replace INVERTER to new-one, and
Check the screen is normal ??
Measured the inveter connector CN303
Pin 1=14V, pin 3 on/off control=5V
(on)
NG, still no screen
Check the Bklt-On relative circuit, R315, Q304,
R311,
In normal operation, when LED =green,
R315 Bklt-On should =0 v,
If Bklt-On no-response when the power switch turn
NG
NG
OK
OK
Measured U201 Oscillator output R215= 50mhZ ?
Replace Oscillator U201
NG , no
transition
OK, has
transitio
Measured X300 Crystal output = 20mhZ ?
Replace Crystal X300
NG ,no
transition
OK
Check Q201 pin 3= 3.3V
Yes
Measured PCLK(L207)
PVS,PHS (pin 73,74 from U200 )
Is there have any transition?
Pclk around 28MHz to 40 MHZ , PVS=60.09Hz ,
PHS around 50KHz-52 KHz ??(refer to input
signal=640x480@60 Hz 31k, and LED is green)
Replace GMZAN1 (U200) or replace
MAINBOARD.
NG , no
transition
If Main Board being replace , please
do the EDID programming
OK