VGA and LVDS on laptop

[jasko_jacker]

Hi all,
I have and old vaio laptop with nvidia 7600, no issue on external LCD but the 17.3 panel show strange colors.
LCD cable (I have tested every wire with tester in ohm) seem not have problem
I have changed LCD but the situation remain the same
Prior to change the GPU chip the question is:
it's possible that a faulty gpu work well with an external lcd and has an issue on lvds signal ?
It's possible to test lcd signal with oscilloscope when the unit is running ?
thanks

[boyebaran]

Re: VGA and LVDS on laptop

hi
may take a photo from strange colors?how about testing lcd panel?
when picture is right in VGA output So GPU chip is fine.

[jasko_jacker]

Re: VGA and LVDS on laptop

These are two pictures of the LCD issue, I have tested the lcd cable with meter in ohm and check continuity pin to pin.
thanks

[jasko_jacker]

Re: VGA and LVDS on laptop

As we know, the LVDS signal and the CRT signal have the balls separated on the gpu. If we assume that the graphics chip is working well, but some of the balls about the LVDS signal are unsolder , why it is not possible that this is the cause of the problem? it is also possible that some components that manage the LVDS signal are faults. In these cases we should have a problem with the graphics driver?
Not always the vision of external monitor exclude a problem on the graphics card, if I'm in error someone can explain why?

[Chungalin]

Re: VGA and LVDS on laptop

Just for curiosity, how does it look with this test image?

[jasko_jacker]

Re: VGA and LVDS on laptop

if I understand the question, this seems ok

[jiroy]

Re: VGA and LVDS on laptop

In case your laptop (you didn't mention the exact model ) is equipped with dual VGAs , then , when one of those is faulty , you can still work on an external LCD while the internal is faulty , or vice versa . In such case , a Gpu or maybe even a removable graphic card repair or replace is a possibility . But , if your laptop is only equipped with Nvidia , then the priority is to change the flat cable first of all .

It's always a possibility that the LCD cable is damaged , even if you tested it pin to pin ..Pin to pin here , i suppose , you tested it for continuity , but such tests do not reveal if some wires are shorting somewhere along the flat ..

[jasko_jacker]

Re: VGA and LVDS on laptop

The owner told me that the problem was the lack of a video signal, but when I turned on the notebook, the screen was working properly. After I installed the entire operating system and run the tests on temperature, the day after the screen showed artifacts. I thought immediately that it concerned the video card failure, but changing it now the screen does not turn on at all.
The laptop is an asus g73sw it has two lvds socket ,one for 3d (5 volt) and one non 3D (3 V) .
I have tested the flat cable with a signal (square waveform ) pin to pin to see with oscilloscope if the wave is distorted but all seems in order.
I have changed the videocard with no result.
I have detected that the 5V switch mosfet it's in order but the signal on the base is missing, if I connect the 5v directly on LCD (it's not a good practice ) the voltage on mosfet's drain disappears and comes back only after removing power adaptor. If I connect the 5V with an external power source I see 0.75 A.
At this point because the lcd has a 50 pin connector (3D) in this moment I haven't another lcd to test or a laptop to test it.
Now I am in doubt whether to buy a LCD flat cable or the entire screen.
What other test could I do?
Thanks