HELP: T61 LCD Blank w Backlight: Ext LCD works VGA/Dual DVI

What do I do?

I first thought it was the nVidia card NVS 140M going kaput on me. But it seems to be working.

Even at boot the internal LCD remains blank (but with some back lighting), while the Lenovo/Thinkvantage / BIOS stuff shows up on External Display.

Is this just some kind of loose connection between the Laptop & Display ?

While I was checking for NVIDIA issues, I found the below as the only Hardware issue 'showing up'/ on System Manager. But it might just something that was due to some Nokia Software I had installed before.

Since the backlight lights, you can rule out an inverter. I'd try an LCD cable, and if that doesn't work check fuses. Reseat both ends of the LCD cable, both at the back of the LCD and at the systemboard as a first attempt at repair.

Yes. When I activate Dual LCD by Extending Desktop on original LCD the screen remains Dark but a backlight kind of makes the Black not so black.

- LCD Cable? - Part number? (I am guessing I can look this up)
- Fuses - Which fuses are we talking about? (I have the HMM so where & which fuses are we talking about)

Looking at the above symptoms of whats working can we rule out that the following items are working fine:
- Video Card
- Inverter.. ?
- LCD Display (Maybe??)

Do share your thoughts.

How did you resolve your problem?

I think I have the same issue: My internal LCD is blank although the backlight is on. Displaying with an external monitor through the VGA port works without any problem. Once in a while, however, the internal LCD starts displaying properly again, but then soon it blanks out.

A loose LCD cable connection can do that. It just happened to me with this X32 I was reassembling. The cable connects to the panel through a very thin ZIF-type connector. It is secured by sticky tape, but can still very easily be yanked out of place if you pull on the other side of the cable too hard. That is why there is a docking point for the cable in the LCD front bezel, to prevent it from moving when the laptop is assembled.

I don't know if the connectors are just as flimsy with other panels, but probably so. Unfortunately, the LCD assembly must be disassembled completely to access the cable connection at the back of the panel. So I would try first the connector on the motherboard (although this one is more beefy and won't easily go out of place).

There is always the chance that the cable is just bad.

Would my above described scenario happen if the nVidia faulty GPU issue from T61 happened?
i.e. Internal LCD not working but External via VGA/DVI works?

Can any of the nVidia faulty GPU failure experienced people share if in their case the external output worked? Or was it complete failure in their case?

There is more than one profile of failure to the nVidia, although this particular one (blank LCD with backlight, external LCD works fine) is not one that I heard of.

I am having the exact same issue as you!

My T61 with NVS 140M works fine with an external monitor through the VGA port, but the internal LCD will not work. I've tried replacing the inverter, and that did not solve the problem. I've also tried re-seating the LVDS cable at both ends, and that also did not solve the problem.

I am thinking the most likely culprit is a fuse on the motherboard?

Can anyone tell me how to locate these fuses and how to check if they are blown with a multimeter?

Thanks!

Interesting. Do you recall, how & when this happened?

PS: Anyone got insights on the fuses?

So I think I figured out how to test a fuse with a multimeter.

Plug one end of the lead into COM, the other into V. Set the multimeter to the "beep" setting for measuring ohms, and then touch either end of the fuse. If the fuse is good, the multimeter will emit a beep.



So, if there is in fact a blown fuse, then the solution would be to either replace it or to solder a good fuse over it.



By the way, does anyone know if we can just bypass the blown fuse by soldering over it?

Yes you can. Do a forum search for 'piggyback'

http://www.google.com/advanced_search?q ... as_qdr=all

For example - viewtopic.php?f=29&t=98523

Where is this Fuse located and how does one get to it?

crashnburn, did you find out about where the fuse is located?

If the backlight comes on, the problem is NOT a fuse. There are 2 fuses involved - one does the backlight and one does the indicators on the inverter. The sugnal leads are not fused. On a T61 with nVIDIA graphics, your problem is probably the graphics chip

I somehow had migrated my HDD to X61T after trimming down some devices in Device Manager e.g. Network Cards (LAN & WLAN) and Video Card etc).

After some tweaking and removing/ detecting some devices and cleaning up some drivers it was working fine on the X61T with the XP Pro _ PreInstall.

Recently I did a fresh Win 7 x64 on an SSD on X61T and thought I'd re-try the XP Pro HDD on the T61 with an external monitor. Lo and behold, it worked on the external monitor and now also works... perfectly fine on the Internal LCD as well.

This is freaky! It was just disconnected and kept off because at the time it would not even show the Thinkpad BIOS/ Logo on Boot. Wierd!

PS: I don't think I made any hardware changes either. I'm wondering if it was due to Adv Mini Dock, but back at the time it would not show the Thinkpad BIOS Boot Logo ... anyhow.. even when powered on without Adv Mini Dock.