T40 display issue [SOLVED]

[Insulator]

Hi guys, my trusty workhorse T40 has developed an issue and I'm looking for a bit of advice.

Symptoms:
Internal display doesn't work (turned off completely), but external monitor works fine.
Upon boot or switching to the internal display, it flashes up an image for a fraction of a second then goes blank again.

I'm guessing it's most likely the display itself or the connector, with GPU an outside chance. My brother has a (fully working) T42 with which I can switch parts for testing, but he lives about 15 minutes away so I won't be able to do anything much until tonight. Just hoping for some tips on what to look out for.

Also, it's probably irrelevant, but I have intermittently had the typical ATI display issues with this machine - but always when using it on an uneven surface and have been able to flex it until it makes contact again... Once I figured out what was going on I've been much more careful to use it on flat surfaces most of the time.

[RealBlackStuff]

Welcome to the forum.
Your T40 has the -by now well documented- loose GPU syndrome.
See the links in my signature.
Only solution: reballing the GPU or replacing the motherboard.
You could try swapping out your complete LCD-lid with the one in your brother's machine, and find out that yours works there, and his not in yours.
If his works in yours, then look at the inverter, easy and cheap to replace. Same inverter for XGA and SXGA+.
Or check the LCD cable, it may be loose at the back of the LCD panel, frayed or broken. Different cable for XGA and SXGA+.

[Insulator]

Yep, I'm well aware of the loose GPU issue, I'm leaving that be for the moment as up until now I've been able to work around it for this machine.

I'm pretty sure the current problem will turn out to be a separate issue, but I was just wondering if the specific symptoms sounded familiar to anyone here (ie whether it's most likely to be inverter, cable, or something else).

[ajkula66]

The GPU has two outputs: analog for the VGA and digital for the LCD/DVI. One can work fine while the other is dead.

My guess would be that your digital side has been affected.

Good luck.

[rkawakami]

Upon boot or switching to the internal display, it flashes up an image for a fraction of a second then goes blank again.

To me that sounds like the inverter is turning off and thus cutting power to the backlight. Question: If you shine a bright light onto the screen, can you see a faint image and does it respond "normally"? By that I mean if you can see the cursor, move it around and launch programs. If so, then the digital signals are still getting to the screen and the problem may not be with the GPU. It would be worth swapping out the lid assembly (in other words, the screen, inverter and cable) with your brother's T42 to see if the motherboard is still working. I believe that any T4x screen can be used on your system but you'll have to get confirmation from somebody with better knowledge with this system.

If swapping the display works, then the root cause of your problem could either be a defective inverter or a dying/dead backlight. Replacing the inverter with a known good unit will determine which is defective.

[ccookie66]

I have the same problem, but I can faintly see the windows when I shine a light into the screen. Thought it was the inverter, replaced it, but didn't help. I'm now replacing the whole LCD screen, because before the problem, the screen would have a red tint to it, and I think that is a sigh of a failing LCD screen.

[RealBlackStuff]

Reddish/pinkish means: replace the backlight/CCFL.
If you are handy and have steady hands, that's a lot cheaper (ca. $15.-) than a whole LCD.

[Insulator]

Just to let you guys know, it was the inverter that had given up. AU$13 later it's working nicely again.

Thanks for the help/suggestions.