Acer Laptop no display (No CPU enable signal to LCD)

[Bskitter]

I am trying to fix a friends laptop.

The problem is that the screen never turns on. Nothing on the HDMI either.

He took it to the Repair store and they quoted him 2500 crowns (100 Dollars)

They played with the BIOS chip and the screen is now iterating over White black and RGB flashes on the screen. (Seems like the Altered BIOS puts the GPU in some test mode)

I bought a new bios of Ebay and received it today.

I have installed it and the screen is now dark again.

I have messaured the voltage for the screen and 3D3v_LCDVDD_PWR is not 3.3 volts.

From what I have tested all the rails to the CPU and GPU are good.

3D3v_LCDVDD_PWR

No boot beep happens either, but this could be default tho.



Above is the schematic of the power on circuit. eDP_VDDEN_CPU is not going high.

Can anybody recommend me something to try/test ?

Laptop Model is Acer vn7-571g

Schematic Available here

https://www.google.cz/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=Acer+vn7-571g+schematic&*

Byron

[orbanp]

Hi Byron,

More info and measurements would be needed!

I take you tested 3D3V_S0, that must be the 3.3V source, or rail voltage, that U5201 switches to the screen, and it is 3.3V ?
Do look at it with a scope, not just with a DMM.

When you had that eBay BIOS and the screen was flashing, did you look at the enable signal, eDP_VDDN_CPU, with a scope?
If not, do check it with a scope!
It is active high, it should have pulsed as the screen was flashing.
If it was pulsing that means that the 3.3V source and the switch is working, and the CPU is not giving that enable signal for whatever reason with the other BIOS.

Also, did the signals look with the scope as "proper" logic signals, going down to the ground, going up close to the 3.3V level, or they looked as something "loading down" the signal?

Good luck, Peter

[Rasz]

The problem is that the screen never turns on. Nothing on the HDMI either.

no hdmi output = its not lcd circuit problem, its broken laptop problem

He took it to the Repair store and they quoted him 2500 crowns (100 Dollars)

and? did he pay? was it a diagnostic/scam fee?

They played with the BIOS chip and the screen is now iterating over White black and RGB flashes on the screen. (Seems like the Altered BIOS puts the GPU in some test mode)

typical cooked nvidia gpu error mode. Im guessing repair store baked your gpu to make it display something

I bought a new bios of Ebay and received it today.
I have installed it and the screen is now dark again.

was it programmed? sounds like you installed blank/wrong chip

I have messaured the voltage for the screen and 3D3v_LCDVDD_PWR is not 3.3 volts.
From what I have tested all the rails to the CPU and GPU are good.
3D3v_LCDVDD_PWR

its NOT the lcd enable.
what was the original problem? how it happened(spill, mechanical trauma, during operation)?
are the leds working when turning it on? whats the power drain from the supply?
its a shit Acer, they are cheap for a reason, your friend needs a new motherboard, or preferably new laptop