a-1502 led functioning

Is there any video which can give full information of the functioning of step by step signal of the led of a 1502. (820-4924). I have dim display. Replaced brightness ic. All voltages missing. If possible pls provide how this circuit works. thanks
 

2informaticos

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You've focused wrong the problem.
As per posted voltages, your eDP output is not even enabled.
You cannot expect backlight, if no image first.

3V at pin 5 and 5V at pins 28-30 (J8300) must appear first; at least in the first few seconds, when machine chimes.

BTW, I was considerring you've measured voltages with internal LCD connected.

Try this BIOS, as is.
 
i flashed the bios with the one you send. I am getting dim display. Voltages onj8300 are as below
1- 0v 3- 5v, 4-5v, 5-2.54v , 6-2.53v, 7-2.53v, 8-0v , 9-2.53v, 10-2.51v , 28,29,30 - 5.16v
 

2informaticos

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Any fault history available?

Post U8310 voltages.
Check diode mode to ground at pin 1 of J8300; w/ and w/o LCD connected.
ALso check Q7700 voltages.
 
u8310 vin - 3.3v on- 3.3v vout - 2.5v
pin 1 with lcd connected - 1.222ohms w/o - same
q7700 pin4 - 12.49v , pin3 - 12.59v 1,2.5,6 - 0v
 

2informaticos

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Jumper why???
Change U8310.

I asked about diode mode reading, not ohm at J8300 pin 1.
Red probe connected to ground, of course.
 

2informaticos

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You can't get ohm value in diode mode; do not write "ohm" after diode mode reading, nor "V".
Don't make same confusion again; that made me think you measured ohm scale, not diode.

Do you get internal image for sure?
DP_INT_HPD and LCD_PSR_EN present?

Remember to check image/backlight signals and voltages ALWAYS with internal LCD connected.
 
yes i am getting image. question mark blinking.
yes i measured in diode mode . forward ie: red probe ground and black on pin 1 - 1.225 is the reading . reverse ie: black is ground and red on pin 1 - infinite. This is same even in ok board.
DP_INT_HPD and LCD_PSR_EN present . I have not checked this signals. I will chk and give you update.
 

2informaticos

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"EDP_BKLT_EN , EDP_PANEL_PWR , all three signals are missing
-----------------------
LCD_PSR_EN --- 0v"
Then is impossible to get L8300 voltage, so no image possible!
PLEASE, post accurate information.
 
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