AOC Vibrant VL7A9DA Service Manual page 17

PANEL-POWER CIRCUIT
check R225 should have response from 12V to 0V
When we switch the power switch from on to off
OK,R225 have response
Measured the U202 pin 5,6,7,8= 5 V?
OK
OK
I
NVERTER Control Relative Circuit
Measured the inveter connector CN303
Pin 1=12V, pin 3 on/off control=5V (on)
NG, still no screen
Replace INVERTER to new-one, and
Check the screen is normal ??
OK
OSCILLATOR BLOCK
Measured U201 Oscillator output R215= 50mhZ ?
OK, has transition
Measured X300 Crystal output R340= 20mhZ ?
U200-DATA OUTPUT
Measured PCLK(L207)
PVS,PHS (pin 73,74 from U200 )
Is there have any transition?
Pclk around 47MHz to 57MHZ ,
PVS=60.09Hz , PHS around 67 KHz ??(refer to
input signal=640x480@60 Hz 31k, and LED is
green)
OK
NG
NG, no Voltage
NG
NG
OK
Check the PPWR panel power relative circuit,
R223, Q200,U202(pin 5,6,7,8)
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 U200-GMZAN1
Check U202 pin 1,2,3,4= 5V
NG
Check U304 relative circuit.(R905,T 300..)
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 on-off,
Replace the MCU
Replace INVERTER-module
& Re-do white balance
NG,no transition
Replace Oscillator U201
NG,no transition
Replace Crystal X300
NG , no transition
Replace GMZAN1 (U200) or replace
MAINBOARD.
If MainBoard being replace , please
do the DDC – content reprogrammed
Ye
Replace U202 ( Nmos, SI9933)