T40: Is this a GPU problem?

[tgrevers]

I just picked up another batch of T40s, and one of them has me puzzled. When I power it on, I see the IBM logo for a split second, then the screen goes dark. I can see the image if I use a flash light, but it has no back light. I'm tempted to swap monitors around to see if the problem moves, with the monitor. Also, if I flex the machine, I can get the video to stop working altogether, getting the machine to lock up. I'm curious if the video flicker at powerup has been seen by others as a GPU problem.

Thanks!

-Ted

[Harryc]

It sounds to me like it has a combination of a defective back light and a loose GPU. For the back light, try running to an external monitor. If the external works, then it is most likey a bad CCFL/back light. If you flex the machine and it locks up, well it's a loose GPU.

[tgrevers]

I was working on this system this evening, it's a 2373-7CU. The external display works fine, and the system works when flexed. So, I'm going to track down a T40 LCD assembly and swap that out.

...so, if anyone has aT40 LCD assembly that you'd like to part with, I'm interested.

Thanks for your input!

-Ted

[jamerslong]

I would suspect an Inverter card before a bad backlight. you said you have a batch of them. you could try swapping out inverters with another one from another laptop. before diving into anything else, and since you have the lid opened up. If the Inverter dosent work then try swaping the LCD's too. why not right?

But I guess it would all be a waste of time if the GPU is bad and you cant fix it.

[poshgeordie]

Am I right in thinking that the GPU has separate outputs for internal and external video outputs? I'm sure I read it on one of these posts somewhere.

When you say it works when you flex it, may I suggest doing the pressing down on the GPU, powering up and checking if video's present.

That may help you to work out the problem area. it's a tricky one this...!