Laptop's display works randomly, external screen always

[martas]

Hi,

I have this problem which drives me mad for some time already. Hope you know more than I. (And sorry for my imperfect English.)

I was using my laptop Lenovo T61 (1440x900) with an external monitor Dell 2209WA (1680x1050) and everything worked just fine - all the combination of primary/secondary screen, only external, only laptop's monitor, both the same picture, or a wide screen over the two monitors.

Suddenly, this problem appeared. Laptop's monitor does not show any picture in 90% of cases. Sometimes it works fine, but just occasionally. Usually it shows neither the first bios splash after turning on, nor Windows 7 running afterward. On the other hand, external monitor works always - sometimes omitting the splash screen but always showing Windows running.

I read a lot already. Back light seems ok, inverter too - as I said, the monitor is working sometimes. And even when it is not, I can seen it is on. I tried BIOS update, without success. Then in BIOS, I checked the display options and could see that it is set to External VGA, so I changed it to Thinkpad LCD, restarted but the External VGA is there again.

In Windows, I installed the newest drivers for Nvidia Quadro NVS 140M, installed the driver for laptop's display, without success. On FN+F7, it is switching, but only from "only external" to "only external" - I can see it switching but nothing changes. Screen settings in Windows is correctly detecting the external screen, but for the laptop's screen most options are disabled. Before installing drivers it said it was a non-pnp monitor. Now it says it is a "mobile PC display".

I reinstalled Vista with W7, hoping it will solve the problem. And it worked, only for a few restarts, unfortunately. Now it is as it was before.

Hope I wrote everything necessary. Please help.

Martin

[richk]

It is hard to diagnose without parts to swap. It could be motherboard (nvidia chip), inverter or backlight. Any of the 3 can cause the problems, although the backlight is not likely if you don't get a red tint at startup. If you have warranty remaining, now is the time to use it. If you don't I would try an inverter because it is the cheapest

[martas]

Thanks for the answer. Am I right if I think that 1) it cannot be nvidia chip since the external monitor is working fine, 2) it cannot be invertor or backlight since I can see the backlight shining through the black screen and from its bottom?

I continued to think about it and nothing else than the simplest cause - the bad connection (contact, cable) - came to my mind so far.

[richk]

Not true. Many nvidia failures I've seen have different results on LCD and external. Sorry.

[martas]

Ok, thanks anyway. There is still warranty remaining, which seems to be the only solution. But how I hate to wait for it repaired...

[martas]

The cause was the motherboard. The guy told me he could not track the problem more specifically. It was replaced and everything works just fine.