T61 display problem

[miamicanes]

[update: the problem described appears to be solved. It looks like it was a loose LCD cable. Basically, the 'display' end of the cable is connected to a socket near the top rear center of the panel, and the only thing holding it in place was a piece of tape that apparently came loose. So... if this sounds like YOUR problem (horizontal lines that wildly change, but don't seem to affect the computer itself, try reseating the cable before you replace your inverter or buy a new panel. And whatever you do, download the T61's service manual from Lenovo first. Being told the correct order in which to disassemble the LCD makes things a lot easier, and I can almost guarantee you won't easily get it put back together again without the manual to refer to. While you're at it, buy a cheap $1.99 caliper from Harbor Freight... it'll make it several orders of magnitude easier to identify the right screw when putting it back together.]

I have a T61 with widescreen 14.1" 1400x1900 display. I bought it used. It worked fine for about 9 months, then started to have intermittent problems with the display. It works fine about 60% of the time, and has problems the other 40%.

At the "mild" end of the problems, it will get horizontal bands that are mostly near the top of the screen. Occasionally, they'll creep down and affect the entire screen (not progressively... it's more like they'll be near the top, then for a few moments the whole display will be affected, then just the top, with random minutes of problem-free operation.

I've noticed that when the whole display is getting corrupted, it doesn't actually update, but the computer itself doesn't freeze. For example, it's doing it right now while I'm typing this. If I keep typing while the display is corrupting, it won't update the display, but when the display returns to sanity, everything I typed will instantly appear.

It affects Windows, Linux, Grub, and BIOS/POST.

Originally, I suspected the backlight or inverter... but then I noticed that the display itself wasn't updating during the worst bursts, which leads me to believe it might be either the internal (DVI?) connection, or the display's controller itself. HOWEVER, Windows Event Log doesn't show anything display-related, and I'm pretty sure that if what's happening appeared to Windows as the equivalent of unplugging a DVI cable, Windows would be logging it somewhere.

It has Intel 965 video, NOT NVidia.

It doesn't seem to be heat-related. The fan works, and there have been plenty of times when I've seen it act up from the moment I hit the power button, and other times when it's worked for hours without any problem at all. Actually, the longer the laptop has been "on", the better it seems to behave.

It's not inconceivable that the problem might have begun after putting excessive weight on the laptop while it was closed. I first noticed the problem a couple of weeks after I started carrying it in a backpack with more books than I probably should have. However, there's no visible damage to the visible part of the display itself (aside from the occasional corruption, of course) -- no cracks, no dead pixels, etc.

Touching the display seems to "bring it back" when it's acting up, but I have yet to identify any particular type of touch that acts consistently.

Does this sound like anything anybody has ever seen, or does anybody have any idea what the problem might be?

[ajkula66]

Although it really doesn't uncover as much as people usually presume, have you tried running the machine with an external monitor?

[RealBlackStuff]

Open up the lid, and check that the LCD cable is properly inserted in the back of the LCD.
If you have one, try a spare inverter.

[miamicanes]

OK, here's an update. The problem still very much exists. Here's what I know:

The problem appears to lie between the motherboard and LCD controller, and NOT between the LCD controller and the rows/columns of the LCD itself.

1. When the screen starts acting up, it does NOT affect an external display connected to the VGA port. The LCD can be completely borked, but as long as I don't look at it and get distracted, everything on the external LCD looks fine.

2. When the screen acts up, there are usually 3 horizontal regions of the screen:

a) The bottom part, which is basically stuck on whatever was being displayed when the noise storm began.

b) The middle part, where there's a "noise storm". The screen tends to update here... kind of. I suspect what I'm really seeing is the same as part C, but the "stormy middle" is the part where it rapidly alternates between nonworking and working fine.

c) the top part, which is completely unaffected.


3. I removed the palmrest and moved the keyboard to expose what appears to be the ribbon cable connecting the motherboard to the LCD controller. When the screen had an episode, I tried touching and pressing down on the cable. It didn't appear to make the slightest bit of difference either way. I didn't tug at it or anything, but the cable definitely flexed and buckled a tiny bit. It didn't trigger it when the it was behaving, and it had no visible effect whatsoever when it was misbehaving.

4. Seemingly complicating any neat theories and throwing a monkey wrench into hopes of a straightforward answer, the problem seems to be several orders of magnitude worse for the first half hour or so after booting up. That's not to say it never happens after the computer has been up for a while, but it's the difference between "the computer is totally unusable for any length of time" and "when it happens, I get annoyed for a few seconds until it goes away". If it's somehow power-related, the first thing I'd suspect is an electrolytic capacitor that's in its dying days (or has already died, if not burst) and doesn't start to work semi-reliably until it's had a while to build up a good, solid charge.


So... I'm open to suggestions for what to try next. I find it hard to believe it could possibly be the inverter, unless the inverter is somehow doing double duty as a power source for the backlight AND powering a circuit that decodes the signal coming from the motherboard, but does not power the display controller itself (otherwise, it would seem that it would be corrupting the whole display, instead of freezing the lower portion and causing a noise/artifact/pseudo-scanline storm in the middle).

[ajkula66]

Can you take a couple of shots and post links to them?

Sounds to me like a panel going bad, but it's hard to say without seeing it...

[Totoro-kun]

Yes, most likely panel itself has gone bad. I have a T60 at work with the same problem you described. After panel replacement it works like new.

[RealBlackStuff]

try a spare inverter.

I told you so... already on Tue Feb 21, 2012 6:14 am
What is so hard to believe about that?

[miamicanes]

^^^ I can grasp why it might be a broken panel. I'm having a very difficult time understanding how it could possibly be due to a failing inverter.

To the best of my knowledge, the inverter does exactly one thing: it powers the backlight/sidelight. Thus, it would seem that the consequence of a failing inverter would be a screen that's dark, not a screen whose fully-illuminated lower portion fails to update below a middle region whose boundaries change from moment to moment.

If the inverter has some function beyond powering the light, by all means I'd love to know so that it can be properly considered as a possibility. It's obvious that I have a problem. However, unless I'm egregiously misunderstanding the inverter's purpose, it doesn't seem to be my problem in this specific case.

Entertaining for a moment the other two obvious possibilities (loose cable and broken panel), how -- exactly -- do I detach and re-attach the LCD cable from the motherboard? Does it pull straight up, slide, latch, or what?

By the way, I appreciate the help

[RealBlackStuff]

I agree that the basic function of an inverter is, to light up the CCFL.
But inverters in a Thinkpad do a lot more: they display various LEDs, control the 'intensity' of the CCFL, and a few more things I'm not able to mention right now.
Any fault on the inverter may cause problems with the rest of the display.
The LCD has column- and row-drivers, which control the vertical and horizontal display. They may be at fault as well.
The cable on the back of the LCD 'slides' upwards into a female connector of the LCD's electronics board.
The cable connector to the motherboard is pushed straight down onto it.
If you remove the keyboard and surrounding keyboard bezel, you can lift this connector up and reattach again. Do this 2-3 times.
That might solve the problem if it was a 'bad' connection.
Reason why I suggest another inverter, is that it is the cheapest and easiest part to replace.
Replacing the cable would be next, then the LCD itself and finally the motherboard.
Your money, your call.

[miamicanes]

Update: a few weeks ago, I removed the bezel, "manipulated" the ribbon cable a bit (no actual removal, just gentle probing and touching it a bit), and was surprised to see the problem go away completely. I put the bezel back on, and it worked flawlessly. For about 2 weeks.

The problem started coming back just like it did the first time... an occasional glitch, then longer ones that went away the moment I touched the panel, to more aggressive episodes that required moving the display on its hinge open and closed, and finally (about 2 weeks later) back to where it was before -- almost unusable for minutes to hours at a time, with various external manipulations sometimes working, sometimes not, and rarely fixing it for more than a few minutes at a time either way.

Two days ago, I took the LCD's front bezel back off, and feel like it's deja-vu. As long as the bezel is off, the display seems to behave. Put the bezel back on, and the glitches start coming back (though not really with a vengeance... yet.)

I'm looking for suggestions for the next logical step. Should I try removing the panel and re-seating the ribbon cable into the connector on the rear of the panel? I'll admit I get a little bit nervous about LCD cables printed onto plastic film connected to panels... ~10 years ago, I destroyed a $700 LCD by disconnecting a flex ribbon cable from a panel that was never meant to be disconnected, so absent something that looks like an unambiguous socket intended for removal and reconnection, I get kind of paranoid

[RealBlackStuff]

As long as there is no power and no battery in it, you can happily take anything in a Thinkpad apart.
Bezel off: means less chance of pressure on, or distortion of, the inverter, which might still be the culprit.
Check that no cable is squeezed in anywhere.
Overheating in the lid is another option, or the CCFL in one corner might start 'burning' through.
Any pinkish/reddish tint in the LCD at startup?

[TuuS]

The cable plugs into the panel on the back and a white piece of sticky plastic (much like tape) is used to secure it, you can peel it off and gently slide the cable out.

If you want a new cable and/or inverter I can help you, depending on how willing you are to repeat this disassembly, it may be a good idea to just replace both, but if you don't mind doing the work repeatedly, then there is no harm in reseating all the parts and see if you get lucky. My gut feeling is that you have a intermittent connection, perhaps a cracked cable or component. Since the act of removing the bezel causes a change, I'd suspect it's the inverter or cable, but it could very well be the panel.

ps. Use some tape to hold the cable in place on the display when you reassemble the lid, they can work themselves loose if nothing is used.

[miamicanes]

Well, I finally bit the bullet tonight and disassembled it down to the bare LCD. It's too late to even think about trying to reassemble it right now, but it looks like the connector between the ribbon cable and panel might have been loose. It's hard to say, because it also might have come loose while I was disassembling it. All I can say is, it was VERY loose, and almost fell out of the connector the moment I loosened the tape.

One thing, though... I went and looked up replacement LCDs, and tripped across an ad that said that there are both CCFL and LED variants of the same panel (the 14.1" 1400x900 widescreen version; P/N 42T0426, FRU 42T0427, LP141WP1(TL)(B8) ). That got me thinking... is the LED variant drop-in compatible? You can see the ad here: http://tinyurl.com/cyt53of

I'm assuming that new LED-illuminated panels have different power requirements (if only because a conventional inverter circuit would be partly redundant & an easy opportunity for later cost-reduction), but this would have been one of the first-generation models... and it seems logical that the first LED panels MIGHT have been designed to be power-able by the same inverter circuits meant for CCFL, if only to build market demand for them by encouraging manufacturers to use them in later manufacturing runs of then-current models, and also reassure them that if they made a million laptops designed for the LED panel, then either ran into a shortage or some fatal flaw, they could switch panels and have a fallback plan to avoid having to scrap a half million partly-built notebook PCs.

Is that the case? Or are the LED-illuminated variants totally and forever incompatible with the T61?

If they ARE compatible, do they actually look better than the original CCFL variant?

I have to admit, I hated nearly everything about the MSI netbook I had before I bought my T61... but its LED-illuminated LCD was absolutely breathtaking. If I could get anything like that kind of brightness from a new panel, it'll be worth the replacement cost for that reason alone, even if a loose cable was my only problem all along.

Failing that, I remember from the last time I looked up replacement 1400x900 14.1" LCDs that there were 3 or 4 that were apparently viewed by IBM as equivalent, but one in particular had about 15-20 nits greater brightness than the others (I don't remember exactly which one it was). Is that a profound difference worth spending 3 weeks hunting to find that specific model, or is it a difference I'd never be able to see, even in a direct side-by-side comparison?

[TuuS]

You cannot install an LED backlight screen in your T61. Some of the newer series had some LED options in the same screen size, like the T500 had a 1280x800 option that used LED backlight, but your T61 doesn't have the proper controllers to run one of those screens even if it did fit. There have been some talk of 3rd party conversions that would allow using LED backlights, but the ones I've read about would need to be installed in a CCFL screen and would require a very expensive modification to get them to work. Maybe the day will come when these types of mods are affordable and widespread, but at the moment I consider them just rumor. My advice is to stick with what you have, if you do end up doing some type of conversion to LED, do it after all the bugs have been worked out, otherwise you're likely to waste a lot of money and perhaps even destroy some hardware in the process.

ps. hopefully all you need is a piece of tape to hold your cable in place and you're system will be back in service

[miamicanes]

Well, I'm happy to report that it appears to have been a loose cable, after all. I reconnected the cable, then used additional electrical tape to firmly anchor the original tape (which was itself firmly attached to the cable, but a little bit dusty and non-adhesive where it was supposed to attach to the plastic flap at the end of the LCD panel) to the plastic flap, then used more electrical tape to firmly anchor the last 4" or so of the cable to the back of the LCD panel to provide additional strain relief & hopefully keep it from coming loose again anytime soon.

I then reassembled the laptop, and it's been working flawlessly for the past 2 days.

I'm not really sure how it became loose in the first place, but this hopefully did the trick. With a little luck, the problem's fixed once and for all.

[RealBlackStuff]

While you're at it, buy a cheap $1.99 caliper from Harbor Freight... it'll make it several orders of magnitude easier to identify the right screw when putting it back together.

It'll make it even easier, if you draw a quick diagram of the part in question (the LCD lid here) and tape the screws to their respective spots.
No fiddling with calipers etc.
Since I take so many laptops apart, I have made spreadsheets with stylized drawings and screw holes for the most used machines.
If one needs disassembly, I just print out the corresponding spreadsheet.
My local Dollar General loves me for all the sticky tape I buy there!