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820-3115 - lcd shadowing & not sleeping when lid closes

I

imoree

New member
Hello Again, this was my brand new 2012 model laptop after 13 months until my cat jumped up and spilled my water over laptop.
immediately pulled apart and dried out with hot air station and removed battery. After a few days i tried to boot up but no backlight. Ended up replacing l8550 , but shadowing is occuring under the screen.
Checked all resistors to lvds and they are all reading correctly. The lid, i tested smc_lid circuit and everything seems to check out ok. I am definately at a lost on this one.
 
Alan.L

Alan.L

Member
Check led returns resistors. Also check if there are any continunty from these resistors to lcd connector.
 
I

imoree

New member
diode mode on all led return lines check out ok √√√
reistors all 0.1 or 0.3Ω -- maybe replace the lvds cable? the l8550 i replaced was brand new from package not a donor board.
 
2informaticos

2informaticos

Administrator
Staff member
"open - 3.4 Volts
Closed - 3.4 volts."
This is the reason for no sleeping problem...

But SMC_LID high doesn't affect backlight.
Do you get steady 25V for backlight?
I recommend you to reflow LP8550 and (very) gently press on top of it.
Seeing it "dancing" is the best way to assure good solders.
I suspect a bad solder on it.

Duke told you check resistance to ground on all return lines; should be all around 600-650, in diode mode.
You didn't reply with the value; let us see what means OK for you...
 
I

imoree

New member
checked resistance to ground but didnt post results and there were within range . Also checked traces. I believe i will reflow the 8550 as i didnt see it dancing for certain.
have backlight , but wont sleep when lid closed, do i need to change ir/sleep sensor? would water have damaged that as well?
no way to test until i get a new one.
 
2informaticos

2informaticos

Administrator
Staff member
Measure directly on hall sensor pins.
Should have 3v on two pins.
If not, there is a broken trace.
The other pin must beep with ground.
Use a magnet and see if any pin reacts.
 
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