a-1502 led functioning

Tara Laptops

New member
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

Administrator
Staff member
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.
 

Tara Laptops

New member
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

Administrator
Staff member
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.
 

2informaticos

Administrator
Staff member
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.
 

Tara Laptops

New member
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

Administrator
Staff member
"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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