T40: problems with display/background light?

[BigCatAndy]

Hello @ all,

some time ago I obtained - rather occasionally - an old T40. The laptop was given to me as defective, it had neither hard disk, nor CD/DVD-ROM. I played a bit with him, and found him in a good shape - I even could start Ubuntu from "Live CD". The only thing which bothers me, is the display. I need to switch the laptop several time on and off in order to get the monitor on. I can easily see, that the monitor remains black for the first 8-10 attempts, and then suddenly the background light switches on, and IBM lg appears.

A friend of mine told me, it had anything with inverter to do. I fear, that I have the known GPU problem. Can anyone give me any hint on this issue? Actually, I see two possible reasons: inverter indeed and/or some cable from board to display is not properly fixed.

Perhaps, some extra information: when laptop starts, it doesn't beep or show any warnings. Ubuntu runs quite smoothly, and shows full 1024x768 resolution. So, I hope, that GPU is OK.

Kind regards from sunny Hamburg,
Andrey

[Harryc]

If you connect an external display to the Thinkpad, does it consistently boot up ok? On the internal LCD, when it does not turn on, does the machine still boot? In other words if you hold a flashlight up to the LCD, can you see the boot or windows screens?

[BigCatAndy]

Hello Harryc,

If you connect an external display to the Thinkpad, does it consistently boot up ok? On the internal LCD, when it does not turn on, does the machine still boot? In other words if you hold a flashlight up to the LCD, can you see the boot or windows screens?

I have no external display at home. Next week I will take the laptop to my office, in order to connect it to the external monitor. The test with flashlight is negative. The LCD panel remains simply black, no action at all.

This week I bought at eBay another defective T40, and I plan to take his parts for mine. I will have to open the laptop - in order to add another 512 MB of RAM. I plan to check the connectors of display and inverter. If they are defective, I will replace them from another laptop. This will work, of course, if my GPU is in order.

I would appreciate any further hints and advices.

Cheers,
Andrey

[BigCatAndy]

Hello Harryc,

If you connect an external display to the Thinkpad, does it consistently boot up ok? On the internal LCD, when it does not turn on, does the machine still boot? In other words if you hold a flashlight up to the LCD, can you see the boot or windows screens?

I tried to connect the external display - it remains black. I pressed Fn+F7, but it changed nothing. I'm not a hardware expert, but I think, that external VGA port IS NOT enabled on the BIOS level. I think, that this port is controlled by OS. Also I noticed, that external monitor doesn't switch immediately on, when connected to my office laptop. It remains off until Windows is booted, and then it shows the login screen.

I would appreciate any further ideas and hints.

Cheers,
Andrey

[Harryc]

Quote from a post by Rkawakami in this thread.

- with the system off, connect a monitor to the external VGA port and turn the monitor on
- power up the system and in about two seconds press the F1 key several times (to get into the BIOS)
- give the system a few more seconds to get into the BIOS menu and then press the Fn+F7 key combination

That should enable the external video. If you still don't see anything, then you probably have a loose GPU.

[BigCatAndy]

Hello,

Quote from a post by Rkawakami in this thread.
...

I did as the post says, and I could see the IBM logo on the external screen. So, I hope, that my GPU is fit. But I will read the thread you mentioned above. Perhaps, I will learn more from it...

Thanks and greetings from Hamburg,
Andrey

[Harryc]

At this point I'd suspect an inverter, LCD cable, or CCFL (back light) as being defective. A fuse on the systemboard is another but less likely possibility.

[BigCatAndy]

Hello @all,

At this point I'd suspect an inverter, LCD cable, or CCFL (back light) as being defective. A fuse on the systemboard is another but less likely possibility.

I also hope, that my motherboard is OK.

By the way, the second defective T40 arrived. With quite the same issue - display remains black. But in this case the seller warned explicitly, that laptop crashes. So, I'm wondering, if I can get anything useful out of two old T40s...

Cheers,
Andrey

[Harryc]

You can try swapping LCD assemblies, but without at least one known working system that is a 50/50 shot. Your T43P is capable of driving that LCD . With that said, if it were my T43P I would not risk it.

[BigCatAndy]

Hello,

You can try swapping LCD assemblies, but without at least one known working system that is a 50/50 shot. Your T43P is capable of driving that LCD . With that said, if it were my T43P I would not risk it.

I'm not going to touch my T43p! My T43p is holy for me, and belongs to the group of untouchable. )

No, I want to try to build one working T40 from those two. I need a lab rat for my Linux-related experiments.

Cheers,
Andrey

[Datashifter]

Just a thought, the tiny switch along the edge furthest from the user, in the area of the "upper left-hand corner" of the keyboard bezel (typically above the area of the "Access IBM" button)... There's a small round peg which pokes down from the LCD screen, and pushes in a tiny switch there, which turns the LCD and CCFL off when the lid is closed.

Could the problem be a bad or sticky switch there?

When I take a small item and push in that switch, my LCD turns off along with the CCFL. If I had an external display handy, I'd test to see if pushing in that switch turns off an external display, however gut feeling says it does not...

I would not be so quick to condem the LCD display itself without looking at all the perepherial circuitry which is both frequently used (that button is pushed every time the lid is closed) and more likely to be worn out over time.

Barring that, if the inverter or the CCFL were to have gone out, the complaintant would still be able to see the IBM logo, and the operating system boot up screen if he/she were to shine a flashlight onto the dark screen, so I highly doubt the issue resides with either the inverter or the CCFL.

Other possibilities would be that the video cable came unplugged from the planar board, or if it was a previously "loved" machine, the video cable could have come unplugged from the back side of the LCD display itself. I would suspect the cable having come unplugged from the planar before it comes unplugged from the LCD, as the cable is held into the LCD's socket by some strong tape - unless it was previously worked on, and that tape was removed.

I recently had to relamp my LCD on my T41, which is what gives me such insight to these other potential issues which would lead to a "dead LCD" display, and knowledge of what a dead inverter or dead CCFL would cause. Bad fuses don't become good after turning the computer on and off several times.

My T41 recently had issues with the CCFL not turning on when the laptop was opened. I would have to push that button 6 to 15 times in a row before the CCFL would kick on and stay on, and there was flickering to the light as well. When the screen was dark, I could still see the IBM logo and Microsoft boot-up screen if I had a flashlight shining onto the LCD.

I took a $7 shot in the dark and ordered a good inverter from eBay. I replaced the inverter, and still had the same issue. I figured it was my CCFL, so I looked around on the net for replacement CCFL's for my T41. I found a website where, for $20 shipped, I could get a new CCFL.

I ordered one, and then thought "I wonder if these pictorials of how to relamp the T41 LCD are accurate or not?" So I took apart my LCD, and found that the problem didn't even require a replacement CCFL - one wire had come detatched from the CCFL's end. I soldered it back on, and the problem was solved.

When the replacement CCFL came in, I thought to myself "eh, screw it," and installed the new CCFL so I wouldn't have to worry about such issues for another 4 years or so, and I have the old but still good CCFL sitting in the shipping container the new CCFL arrived in.

Just my two cents, check the little switch, and both ends of the video cable to make sure they're both fully seated. I can easily see how something sticky (coffee, soda, what ever) can get spilled and drip down into that switch, leading to a malfunction...

[BigCatAndy]

Hello Datashifter,

Just a thought, ...

thanks for your ideas! Really, I appreciate any hint, and I'm glad that there are people willing to help.

That little button is a physical sensor (so to say) of the lid state - closed or open. I will check it, for sure.

And with cables... Both laptops were several times disassembled and reassembled.Yyou may see, that some parts do not match perfectly and are just tightly screwed together. I can imagine, that someone simply did something wrong with inverter or cable, and now it needs several attempts to start.

I plan to take care of those "cadavers" on the coming week-end. I hope, I will be able to report success on Sunday evening...

Cheers,
Andrey

[poshgeordie]

Hi Andrey

You've got some difficult problems here!

It is possible to have a graphics chip problem on your boards.
The reason is that on the GPU there are two separate video outputs, a digital internal output and an analogue external one, and it only takes a few unsoldered pins on one part of the chip (there are nearly 700 after all!) to lose one of the video outputs but have the other.

Please try the following but don't do it too often since you can damage the GPU solder balls:
Power off your TP .
Connect the internal screen .
Press quite hard on the GPU whilst powering up the TP.

If you get a display on the internal screen then its very likely that you have a GPU soldering problem.
If you don't get any display then it could well still be a GPU problem but it's worth trying this trick.

You've got a PM too!

[BigCatAndy]

Hello poshgeordie,

Hi Andrey

You've got some difficult problems here!...

nice comment, it makes me really optimistic.

So, the week-end is coming... Let's see, if I manage to solve the issue..

Cheers,
Andrey

[poshgeordie]

Weekend work is always helped along with a few lagers....especially those German ones!

Good luck!

[BigCatAndy]

Hello @all,

Hi Andrey

You've got some difficult problems here!
...
Please try the following but don't do it too often since you can damage the GPU solder balls:
Power off your TP .
Connect the internal screen .
Press quite hard on the GPU whilst powering up the TP.
...

it was a good hint. I really have problems with the GPU. Now I think about further steps...

Cheers,
Andrey

[Datashifter]

...
it was a good hint. I really have problems with the GPU. Now I think about further steps...
...

Sorry to hear that it ended up being the GPU issue...

Best of luck to ya!

[BigCatAndy]

Sorry to hear that it ended up being the GPU issue...

Best of luck to ya!

Thanks.

Cheers,
Andrey