ACER AN515-51G no display

[Garibean]

Hi

Here i am again, stucked during my repair journey, again with a laptop that does turn on but shows no display.

ACER A515-51G motherboard LA-E892P REV 1C

I tried 3 different BIOS just to be sure but nothing...
I disabled On board RAM (of course i have an other stick of ram inserted), did the UMA procedure to exclude the DGPU

Here what i have so far :

+5VALWP : 5.20V
+3VALWP : 3.3V
+3VS : 3.3V
DRAMRST : 0V
+VCC_CORE : 0V
AC_PRESENT : 3.3V
VGACORE : 0.9V
VGACORE_EN : 5.2V
PLT_RST : 0V
PLT_RST_BUF# : 0V
pch_pwrOK : 3.2V
PSYS : 0V
H_CPUPWRGD : 0V
+VCCIO :1V

Schematics : https://www.badcaps.net/forum/showpo...37&postcount=1
Boardview : https://www.badcaps.net/forum/showpo...13&postcount=5

Any ideas ?

[mcplslg123]

Re: ACER AN515-51G no display

No pint measuring PLTRST# when even vcore is absent. What about 1.2V/1.8V/2.5V rails?UC5-voltage on pin 1-2/6-7/8-9/13-14?
UC6,pin6 voltage?
UQ1-Working?
VCCSA present?

[Garibean]

Re: ACER AN515-51G no display

Nothing seems to stand out, maybe the 11V and 10.5V from UQ1 but i don't know what is it

+2.5v : 2.5v
+1.8vs : 1.8v
+1.2p : 1.22v

uc5
1 : 1v
2 : 1v
6 : 1.8v
7 : 1.8v
8 : 1.8v
9 : 1.8v
13 : 1v
14 : 1v

uc6
6 : 1v

uq1
1 : 5.2v
2 : 5.2v
3 : 3.3v
4 : 5.2v
5 : 3.28v
6 : 3.31v
7 : 3.3v
8 : 3.3v
9 : 3.3v
10 : 10.5v
11 : Gnd
12 : 11.06v
13 : 5.2v
14 : 5.2v

vccsa : 1.04v

[mcplslg123]

Re: ACER AN515-51G no display

Ec_vccst_pg ??
Vr_on-??

[mcplslg123]

Re: ACER AN515-51G no display

Measurement at post#3 are all correct. Share resistance to GND on Vcore coil also.

[Garibean]

Re: ACER AN515-51G no display

ec_vccst_pg ??
Vr_on-??

ec_vccst_pg = 1.0v
vr_on = 3.29v

PL907 VCCSA = 38 ohm
PL904 vcccore = 14 ohm
PL906 vccgt = 12 ohm

I forgot to say, sometimes, the board does not start. The board turns on for 5 sec then turn off. I do not know what to think about that

[Garibean]

Re: ACER AN515-51G no display

Little update, i checked the PQ903 MOSFET, it's a AON6314, i measured 16ohm between drain and source, could it be the problem ? it looks like a low side mosfet

[Techtiger]

Re: ACER AN515-51G no display

Little update, i checked the PQ903 MOSFET, it's a AON6314, i measured 16ohm between drain and source, could it be the problem ? it looks like a low side mosfet

Since the low side Fet it may be necessary to remove it and test again. By doing so, you can determine if the Fet is the root cause of the problem and find a solution to fix it
& find out why H_CPUPWRGD : 0V

[Garibean]

Re: ACER AN515-51G no display

Since the low side Fet it may be necessary to remove it and test again. By doing so, you can determine if the Fet is the root cause of the problem and find a solution to fix it
& find out why H_CPUPWRGD : 0V

I removed it and replaced it with an other one, nothing changed... i'm clueless on this one :/
it maybe was useless to measure this mosfet because the drain part of the mosfet is connected to cpu and there is a low resistance to the cpu anyway :/

i don't know what to do, i'm a beginner with laptop repair so i learn everyday, but sometimes i'm stuck like this and it's frustrating i just want to toss to the bin the whole board ^^'

(little edit i have 3 ohm and the cpu and not 10 of ohm)

[Techtiger]

Re: ACER AN515-51G no display

Trace the pin 74 SIO SYS_PWROK what voltage do you have there

[mcplslg123]

Re: ACER AN515-51G no display

If you have a SIO programmer, flash SIO.

[Garibean]

Re: ACER AN515-51G no display

Trace the pin 74 SIO SYS_PWROK what voltage do you have there

I have 3.29V on SYS_PWROK !
Little update but now the amber led for charging does not turn on anymore... this signal come from te SIO

If you have a SIO programmer, flash SIO.

Unfortunately i don't have one, what signal can i look on an oscilloscope to be sure that's it's the SIO that is in need of programming ?


I have an other problem, i can't take measure to the chip PU301, this is a bq chip for the battery (BQ24735RGRR), the moment my multimeter probe touches a pin, the laptop turns off, is this a normal behaviour ? i am not making any short, i'm even measuring on a resistor to try to not measure on the BQ

[Garibean]

Re: ACER AN515-51G no display

Update : upon testing i have sometimes the +vcccore that works... it's random i don't know why it shows itself

[Garibean]

Re: ACER AN515-51G no display

Update 2 : ok this one is tricky ! I followed this guide about the first reset signal https://www.badcaps.net/forum/showthread.php?t=44779
i test the frequency of the oscillator to see if i have 32.768khz, i have it on the oscillo, i start the board while mesuring on the oscillator and the the +vcccore is present !!

And it works everytime with the oscilloscope, i guess the oscilloscope adds a paralel resistance to the quartz and so enough current can flow through thanks to the paralel resistance of the oscilloscope !
So what can i do, about this one, change the resistance, change the quartz YC2 ?

[valvassori]

Re: ACER AN515-51G no display

PU 902
Pin 2 = ?
Pin 3 = ?
Pin 4 = ?
Pin 7 = ?

[Techtiger]

Re: ACER AN515-51G no display

Update 2 : ok this one is tricky ! I followed this guide about the first reset signal https://www.badcaps.net/forum/showthread.php?t=44779
i test the frequency of the oscillator to see if i have 32.768khz, i have it on the oscillo, i start the board while mesuring on the oscillator and the the +vcccore is present !!

And it works everytime with the oscilloscope, i guess the oscilloscope adds a paralel resistance to the quartz and so enough current can flow through thanks to the paralel resistance of the oscilloscope !
So what can i do, about this one, change the resistance, change the quartz YC2 ?

Good job change the quartz YC2 first

[Garibean]

Re: ACER AN515-51G no display

I changed the quartz and i have now 1v on the +vcccore every time
But i still can't get a screen yet but it's getting there !
What is the next step ?

[Garibean]

Re: ACER AN515-51G no display

An other update, i just have to wait a little to get a screen !
So this is a successful fix, it was only the oscillator YC2 !
Thank you everyone for your help, i love this community and i'm learning every day something new !