Asus UX305CA no screen

[Garibean]

Hi

I have a Asus UX305CA :

-Doesnt boot
-No display
-Power led ON
-CAPS lock LED ON but no reaction when pressing it, it stays on
-Battery LED blinking green 2 times then repeat

What i have :

+0.6V : 0.62V
VCCCORE : 0.76V
VCCGT : OV
+1.2VO : 1.2V
+3VO : 3.34V
+3VSUS : 3.3V
+3VAO : 3.28V
+3VA_EC : 3.3V
+5V : 5.16V
+5VO : 5.16V
+5VAO : 5.16V
+5VSUS : 5.16V
+12V : 14V
+12VSUS : 14V
AC_BAT_SYS : 10.91
P_CHG_LX_30 : 10.9V


+3VADSW_ON : 3.28V
+5VSUS_ON : 3.29V
SUSWARN# : 3.3V

ALL_SYSTEM_PWRGD : 3.3V
VCCIO_PWRGD : 3.3V

PS_ON : 3.28V

BUF_PLT_RST : 3.3V
PM_RSMRST#_PCH : 3.3V
PM_RSMRST# : 3.3V


I also tried to program a new BIOS but no changes...
I don't know what to check to find the problem here, any tips ?

Kind of schematics : https://www.badcaps.net/forum/showpo...38&postcount=9

Boardview : https://www.badcaps.net/forum/showpo...61&postcount=2

[mon2]

Re: Asus UX305CA no screen

+12V : 14V

???

[Garibean]

Re: Asus UX305CA no screen

That's not a mistake, i have 14V on the +12V, i don't really know what i can do with that :/ i just saw that this voltage is used for a mosfet gate for a 3V line, is that a problem ?

[piernov]

Re: Asus UX305CA no screen

Unregulated charge pump output, shouldn't matter.

[mcplslg123]

Re: Asus UX305CA no screen

DRAMRST# status?

[Garibean]

Re: Asus UX305CA no screen

Unregulated charge pump output, shouldn't matter.

Yes, i just learned about charge pump with schotky diodes thanks to you ! I didn't know that this circuit existed !

DRAMRST# status?

On DRAM_RESET# or (TP_DDR3_DRAMRST_N), i have 0 V when turning on the laptop and 7.34 MOhm to GND. I guess that's not a good sign, this signal come from the cpu... or maybe this is normal ?

[mcplslg123]

Re: Asus UX305CA no screen

Yes,cpu will reset the ram.It could be bios issue also-so try flashing a clean me bios after making backup of your original. Do check ram area for corrossion.

[Garibean]

Re: Asus UX305CA no screen

I tried a bios with a clean ME but nothing more...
The ram are soldered to the board so i can only look the 2 little ram chips and that's all :/
Any other ideas ?
I forgot to say, when i reset the bios and then i turn on the laptop, the laptop try to start then turn off then restart and then i have the green led blinking twice

[mcplslg123]

Re: Asus UX305CA no screen

Try disabling the onboard ram.

[Garibean]

Re: Asus UX305CA no screen

I don't know how to disable the onboard ram on this model, and i don't think the laptop will work at all given that there is no way to add a stick of ram if i disable the onboard ram

[koby058]

Re: Asus UX305CA no screen

reflow ?

[mcplslg123]

Re: Asus UX305CA no screen

Oops, if there is no ram slot,disabling onboard ram is out of question.

[Garibean]

Re: Asus UX305CA no screen

Update : I tried to reflow the ram chips, now i have a short between the 1.2V line and gnd... maybe the reflow wasn't a success (or even did the short) or even one of the ram chips was dead ? or the cpu
I will try a voltage injection tomorow with a thermal camera to see anything

[Garibean]

Re: Asus UX305CA no screen

Nothing on the thermal camera and 6 amps 1v...
So i guess the reflow was not a success, the 1.2V and Gnd line are really close so that explain the short circuit