Model: Acer Aspire 5755 (i5 Intel Graphics)
Motherboard: P5WE0 - LA-6901P
Symptoms : Power on the laptop but nothing on the screen.Fan spins/DVD-RW spins/ Lights up/ Battery Charging But no HDD LED light up.No boot loops or shut downs.

Other details:
01. Northbridge has higher temperature no other chips are over heating.
02. BIOS (Main + EC) Re- programmed.
03. +3.3VALW and 3.3VS / +5VALW and +5VS available.
04. PL20 = 1.17V, PL21= 1.15v, PL18=0V (+VGFX_COREP)
05. Ground to PL18 multi-meter shows 010
06. RAM and CPU Changed.

Here are the pin volatges of PU12
pin22 (VDD)=5v
pin23 (VIN)=18.98v
pin7 (VR_ON)=3.3v
pin8 (PGOOD/VGATE)=3.3V

pin2 (IMONG/GFXVR_IMON)= 0V
pin3 (PGOODG/GFX_CORE_PWRGD)=0V

Could you please someone tell me where should I start for a solution for this matter.Thanks

exchange isl 95831.

Good idea but replacing ISL95831 is the last thing I expected to do. Before that I need to know why +CPU_CORE is available and +VGFX_COREP not available.

+VGFX_COREP will be only afer some post codes.

I had a similar situation. i replace isl and kbc. if isl - bad, to usualy +VGFX_COREP bad.

I cannot understand what you are saying.Sorry if I am mistaken.



I dont have ISL now. I will change ISL and let you know the result. But if anyone had this problem please advice me.

First, system power on, all voltages up, except +VGFX_COREP
Second, system start, you must have some POST's, only after this +VGFX_COREP up too.

Ok. I got it now. There is no POST screen or anything. Just start the laptop but no display.
So in this case what are you suggesting to do. Because I thought +VGFX_COREP is the problem.
If you are correct now i think KB might be bad for some reasons.
What do you think? Where to start find this problem?

Check LAD0...LAD3 via oscolliscope, PLT_RTS# must be high, check what Flash ROM's is reading

My oscilloscope has broken.So i ordered new one but it still haven't received.I will post the results when it got here.thanks

OK I got my new oscilloscope and if i use debug card can I figured out the problem more specifically. Also how do I read whats ROM is processing, I mean signals..?

Check LAD0 signal. What do you see?

Everythings fine after reballing the south bridge. Acer V3 and E1 core i3 models always have this problem. Whenever EC not producing SUS_ON signal, most probably PCH is the problem in this case.