T40 Screen Problems - Inverter, cable, screen or backlight?

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MaverickX · #1 Post by **MaverickX** » Wed Jan 24, 2007 2:40 am

So my T40 screen has been giving me the same problems I've read on other posts. Turning it on, I can see the "IBM Thinkpad" bootup logo, but its extremely faint. Same with the Windows XP startup logo after that. Once I'm in Windows, I can't see anything.

After making sure all the cables were in properly, I replaced the inverter board, but still no real luck.

Right now, if I turn the machine on and leave it plugged in for about 15-20 minutes, the screen will power-up and gradually get brighter until normal display. This happens pretty much everytime, after the same time period.

So, whats my next step? Should I replace the screen? The backlight? The screen is about $200 online, so I'd like to be fairly certain that this would fix the problem before I buy the new XGA screen.

#2 Post by **GomJabbar** » Wed Jan 24, 2007 5:58 am

Sounds like the backlight itself to me. If you are mechanically inclined you could try and replace it yourself. I have not tried this yet, so I cannot give any personal experience. From what I have read, it is not the easiest of replacement jobs.

The first link below is for replacement lamps, and the second is a service that will replace it for you for a flat fee.

LCD CCFL Replacement Lamps

Backlight Replacement Service

#3 Post by **rkawakami** » Wed Jan 24, 2007 6:49 am

Gaa! It sounds like the same problem I have with one of my 600Es. Turn it on, no backlight at all (but there IS pixel activity; can see it by shining a bright light on it), external video is okay. Wait about 5 minutes and presto, the backlight fires up! I've checked and/or replaced the inverter, the Sub Card (i.e., the lid switch), the entire top lid (LCD panel and cable) and still the problem is there. Shut off the display by switching from LCD to external video with the Fn+F7 sequence and then re-activate the LCD, and the "timer" resets and I have to wait another 4-5 minutes.

I'm convinced that the problem is with the motherboard although I have no idea what might be wrong. I've got two other 600Es now so I can start playing around with them (as time permits).

You say your screen "gradually" gets brighter. Does it start out pink/red, then turn white? If so, that's an indication that the backlight is near the end of its life. If it's more of a "dimmer" switch-type of increase of brightness, then that seems to be a voltage problem (the inverter is not putting out enough juice to the backlight).

My suggestion to you is to check the following:

- The lid/display switch. Not sure where it is on the T40, but with the system off, press it down several times, quickly, and see if that helps
- When the backlight finally turns on for you, use either the Fn+F3 (shut display off) or Fn+F7 (switch to external video) to kill the backlight. Wait a few seconds and then if you used Fn+F3, just press any key (say Fn) and the backlight should turn back on. If you used Fn+F7, press that sequence again. There should be three settings; LCD, external video, LCD+external video. You may have to press Fn+F7 a second time.
- If the backlight does not turn on, shine a light on the LCD and see if you can detect any pixel activity.
- When the backlight is on, use the Fn+Home and Fn+End sequences to vary the brightness of the LCD. Does that seem to work correctly?

MaverickX · #4 Post by **MaverickX** » Wed Jan 24, 2007 9:02 pm

rkawakami - Wow, thanks very much for the detailed response. Sounds like my laptop is experiencing very similar problems, but a few things make me uncertain whether its the backlight or the screen, here are my responses to your suggestions

1. It doesn't get pink, its either on, off or dim. When it gradually gets brighter, its gets to the normal brightness setting in under a minute after it decides to actually switch on.

2. If the screen has decided to power up, then shutting off the screen via Fn+F3 or Fn+F7 doesn't seem to affect anything. I can reactivate it with the same key combination with no problem.

3. Using Fn+Home and Fn+End to vary the brightness seems to operate normally

4. The time I have to wait for the screen to come on is about 5-15 minutes.

So far I've only replaced the inverter without any success.

GomJabbar - I'm willing to try the backlight since its a relatively cheap repair. I've only used a soldering iron once in my entire life, but I've been able to find some pretty good instructions online (as well as the site you linked). Only thing is that I'm afraid it might not be the backlight since I haven't noticed the notorious "pink/red" hue that seems common to backlight problems.

#5 Post by **rkawakami** » Wed Jan 24, 2007 10:27 pm

Before spending any money, try the usual things (if you haven't already):

- Re-seat the ribbon cable that is attached to the motherboard that goes to the LCD. Unplug it from the motherboard and then re-insert. Be careful that you do it according to the instructions in the Hardware Maintenance Manual (lift it straight up).
- Make sure that the lid switch is working correctly. When the backlight finally turns on, push the switch down. Again, since I haven't used a T40 before, I'm assuming that there's one somewhere near one of the hinges. It should turn off the backlight and maybe even put your system into standby or hibernation. If so, wait until it's done, then release the switch. If that returns the backlight to normal, that's not your problem.
- Figure out if there might be any other connections from the LCD (or lid switch) that goes through another connector and perform the same re-seating process.

If no luck and it still takes several minutes for the backlight to turn on and if this were my system, then I would proceed as follows:

- Buy a replacement CCFL; $15-$20 I think.
- Buy the cheapest, known dead LCD panel which fits your T40. It's alright if it's totally broken; all you need is the small connector that the backlight plugs into the inverter board. I would take the time to track down who makes the connector and see if I could source it from a distributor, but buying a dead panel is probably easier. Cost? Maybe another $20, but might be hard to find even on eBay.
- Attach the connector to the bare CCFL tube, making sure that the ends are well insulated. Fire up the system. If the tube lights consistently right away, then the problem IS the backlight in your panel. You then have the fun job of disassembling the panel to replace the lamp. If the new CCFL doesn't work normally, then the problem is on your motherboard or elsewhere in the system.

or...

you could simply buy a new or refurb panel for the T40 and just plug the CCFL connector into your system's inverter. If it works, swap panels. If it doesn't, sell the panel back on eBay or here because you'll need the money for another motherboard or some troubleshooting tech

.

MaverickX · #6 Post by **MaverickX** » Tue Mar 13, 2007 9:14 am

*Bump* and a followup question:

Does a replacement screen include a new backlight inside? Since I don't know which is the problem (already eliminated the inverter board by replacing it) was hoping I could just kill two birds with one stone and replace the screen AND backlight in one swoop.

mitchellst · #7 Post by **mitchellst** » Tue Mar 13, 2007 1:34 pm

I would assume that it would depend on where you get it... but IBM doesn't give out LCDs without them, so if you get one without a backlight, someone removed it.

Msmax · #8 Post by **Msmax** » Wed Mar 14, 2007 1:10 pm

The backlight tube is built in the bottom part of the LCD screen assembly. I do not know of any suppliers of LCD screens without backlight as it is more or less useless.

If you need the connector to try with an external tube, then send me your address. I have several broken screens of which I can send you a connector.

Do you have a 14"or 15"screen?

Regards, Msmax

MaverickX · #9 Post by **MaverickX** » Wed Mar 14, 2007 4:58 pm

Wow, thanks for the offer Msmax, I really appreciate it. But I think I'd rather avoid the soldering all together and if i was going to do it, just replace the whole screen assembly (backlight and all).

Not totally sure if I'm going to do it, since it would cost me about $200 for the screen + shipping, but now I just saw this deal

http://www.buy.com/prod/ibm-thinkpad-t4 ... 29262.html

for $500, essentially the same system that I have (smaller hard drive). So I might just avoid trying to replace the screen since I'm not even 100% positive that will end the finicky screen problem.

#10 Post by **GomJabbar** » Thu Mar 15, 2007 8:12 am

These guys will replace your backlight or inverter - whichever is needed for a flat rate of $115 on a 14.1" display.

http://www.moniserv.com/doc/laptopscreen.html

MaverickX · #11 Post by **MaverickX** » Thu Mar 15, 2007 2:30 pm

Wow, thanks GomJabbar, looks like a pretty good deal.

Has anyone used these guys before? Just wanted to see if I could get some feedback before sending in my precious T40

T40 Screen Problems - Inverter, cable, screen or backlight?

T40 Screen Problems - Inverter, cable, screen or backlight?

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