T23 LCD troubleshooting hints

[egemme]

Hi,

I have a LCD problem on my T23. It works 1 time out of 5 and once working, it goes out after few minutes of operation. It first starts to flicker, more, and more and goes blank. I read somewhere this is a well know problem caused by a broken cable at the hinge level, so I replaced the cable but still have the problem.

Clues I have gathered so far:

1. The external VGA port works without any flaws, so this tells me that the Video Adapter/main board works well. During being on the external screen, I played a lot with the screen toggle to make sure this was not an issue.
2. The backlight stays on, this not a problem.
3. I have put back to old cable and new back and forth 2 or 3 times with the result the screen was back for a little while.

Please someone help me to find out:

1. Is it likely possible that I've got a lemon cable? It was new but looked to be a broker part, not an IBM original.
2. Is it possible that I'm having dirty connectors? On the LCD back or main board?
3. Does the LCD itself could produce these symptoms?
4. Any other possible failure I didn't list here?

Please advise on these points so I don't buy a LCD this is not the cause.

TIA

[rkawakami]

Welcome to thinkpads.com!

I guess I'll take a crack at this...

If the backlight is on (solid white, no flickering) and the screen goes from showing a good image to one of all-white, then the problem is in the way that the video signals are getting from the motherboard to the individual pixels on the LCD panel. The causes can be these:

- motherboard
- video ribbon cable
- LCD panel

Starting from where the signals originate and going to where they control the pixels, the problem could be on the motherboard in a couple of different places. The video graphics chip could have an internal problem which affects the LCD signals and not the external VGA port. There could be a bad solder connection on the bottom of the graphic chip (a known problem for some T4x systems but not one I've seen too often with the T23). The connector on the motherboard that the ribbon cable plugs into can have one or more pins broken or dirty. The ribbon cable could have a broken trace somewhere along its length. The connector on the back of the LCD panel can have a similar problem with broken or dirty pins. And finally, the LCD panel may have a bad circuit board which is causing the problem you see.

In troubleshooting problems like this, I would first start off with the cheapest solution. This is looking closely at the connector on the motherboard, the ribbon cable and the back of the LCD panel. As you have already replaced the ribbon cable and still have the same problem, the chances of you obtaining another cable that has the same issue is pretty small. So for now, let's assume that both cables are good.

Take a magnifying glass and inspect the white connector on the motherboard in which the ribbon cable is attached. You should see vertical gold contacts on either side of the plastic centerpiece. Make sure that all are present, shiny and straight. If some of them look dull, you can use a small amount of isopropyl alcohol on a cotton swab to clean them.

On the other end of where the ribbon cable goes, take a close look at the connector on the back side of the LCD panel. You can use a small mirror and flashlight to get a better look.

If nothing appears to be amiss in either connector, re-assemble and check the system again. If the problem persists, you may be able to try a couple of more things:

- Move the entire lid back and forth along the hinges to see if that fixes it or makes it worse
- Gently twist the panel. By this I mean to push the top left corner back (away from you), while pulling the top right corner forward (towards you). Repeat in the opposite directions.
- Gently press along the outer edges of the TOP of the lid (not the actual panel itself or the bezel surrounding the screen).

Does this help or hurt?

Also, does the problem also show up if the system is booted to the BIOS screen (press and hold F1 while turning the power on)?

[egemme]

Thanks Ray for the fast response. Your info was valuable and allowed me to both understand few things a little better.

There's one thing I didn't mention. Every time I was giving a new boot attempt after completely open and re-close the whole thing, I had to struggle with a two beep mobo error. The fact I didn't have a screen to understand let me think I had a severe error. This was just a bad date/time caused by the removal of BIOS backup battery...!!! Phew.

Now, the problem. After re-re-re-re open, re-re-reseat all connectors, and even this time did an inspection and cleanup of the mobo connector -- the one on the LCD is not obvious to clean -- I put everything back and still don't have a screen. But the external VGA works flawlessly. Now I understand that ext VGA and LCD takes different routes from the video card and bad soldering in the LCD route might be or bad guy.

Gently twisting the lcd panel didn't help. Flipping the lid open and close several time didn't neither. Also, when repluging the lcd cable, I did apply a good pressure all around to make sure there are no loose parts. Nothing seems to help. Now how to discrimitate the problem between the mobo and LCD without spending a buck? I'm affraid there's no way, do you? I have a full functional A21e here but unfortunately, LCD fru's are completely different.

Any other clues?

[rkawakami]

Okay, with all of that troubleshooting out of the way, I'm left with one other thing which may help...

It is on the dangerous side and if you are not careful, could lead to more problems/additional damage. Please read the following carefully and if something is not clear, ask me for clarification.

Since you are now an expert in taking the system apart , and we need to try to determine if the problem is in the motherboard or the LCD panel, here's what I would do:

- With the system off and AC adapter disconnected, remove the following: battery, hard drive, Ultrabay device (CD or DVD), keyboard and keyboard bezel.

- Re-attach the keyboard (and not the bezel) by simply aligning the connectors. Push down around the "Y" key to insure that it's seated properly.

- Make sure that no external monitor is plugged in.

- Plug in the AC adapter and press the power button.

- Since the system now has no bootable device it will take about 30 seconds before you would see the "Operating System not found" message.

- If the display is working normally, just let it sit until it acts up. If the display is NOT working properly, then grab both sides of the keyboard and carefully remove it by lifting straight up.

- Once the keyboard is out of the way, gently press down on the video graphics chip near where the middle of the "space" key was. It can be identified by "Super Savage/IXC", the "S" in both Super and Savage is long and curvy. On my "map" of the top side of the T23 motherboard, it's located at F6:

http://www.rkawakami.net/ibm_t2x/mobo_top_72_legend.jpg

- To turn off the system, simply disconnect the AC adapter.

Does any amount of pressure on the video chip fix the display issue? If so, then I'd say that it's not soldered down all the way to the motherboard and your LCD is probably fine. If this is the case, it's not too easy to repair. Some people have had success with the T4x systems in using heat guns to re-flow the solder. If pushing down on the video chip does not fix the problem, there could still be an issue with the motherboard somewhere else OR the problem might be in the LCD panel.

If it comes down to a toss-up between the LCD panel and the motherboard, then I would choose the LCD panel to replace simply because it is the easier one to swap out. I've been able to push back the existing panel/lid, unplug the ribbon cable and attach a completely separate lid assembly to the motherboard while holding on to it with one hand.

[egemme]

Hi Ray,

Thanks for the flowers. BTW I'm a programmer but used to do HW as well but in much larger machines such PC and IBM i5 (fka AS/400). Laptops are so tight...

In the meantime you wrote your reply, I did a little test. I gently opened the LCD bezel so I can lift it up from the assembly enough I can slide my hand beneath. I booted up and been able to make the screen goes and come back just by a slight pressure on the back of the LCD panel about a inch diagonally beside the LCD connector. Anywhere it is, it seems that pushing a bit the LCD main circuit make it jump and go back. I tried to push every places of the 3 by 3 inches circuit including the connector area and I'm very confident this is not the connector to makes the screen go, but a finger tip area located upward-left of the connector with the back of the LCD facing you.

Is this repairable or it involves microsoldering that will cost me an arm?

Thanks

[rkawakami]

Eric,

I haven't looked too closely at the circuit board in the LCD the couple of times I have had a panel out in my hands. You may have to disassemble the panel to get at the back side of the PC board (I assuming that it's double-sided) Or, you may be lucky and find your loose or broken connection right on top. I'd say that all of the components would be of the surface-mounted variety and that a small (25W) soldering iron with the finest tip you can get, may be useful. If the problem connection is on a component that uses ball-grid array (BGA; solder balls on the bottom side of the package), then we get back to the "heat gun" method of repair. If the problem is a broken trace on the board, then it's possible to repair by scraping the solder mask (green film) off the copper trace and soldering a wire across the broken area.

In any event, it sounds like you now know where your problem is.

[phool@round]

Eric, Ray,

I don't mean to jump in here because the two of you are well on your way to solving an interesting issue. I've been reading along (always something new to learn) and I remembered that I have a spare screen.

In front of me I have a Samsung (LTN141XF -L01). IBM P/N 46L2293, FRU P/N 46L2292.

On this particular T23 panel it has a clear sheet protecting/covering the LCD circuits and components underneath. I noticed a few rub marks on that clear sheet over the taller components from the LCD cover. A little detective work might find the exact component that needs the attention.

If you do own a Samsung (I hope) there is only one solid capacitor marked "C29" in the area you've pointed to Eric. Also Samsung has used a thin gold flexible foil for the circuits. Ray's recommondation of a 25W soldering iron with a very sharp tip would indeed be all you need to reflow the solder. A magnifying glass would be helpful to initially check the component, and afterwards to watch your soldering.

Someone suggested to make a tip very sharp is to put it in a electric drill and use a file to shape it quickly. There is nothing better than a long pointed tip for small detail work.

[rkawakami]

Thanks for that info! Indeed, if it's a simple matter of one of the passive (resistor, capacitor) components being loose, it is possible to use a regular soldering iron to re-attach it. A good magnifying glass will be useful in examining each part to see if there's a small crack in the soldered connection. If it's an integrated circuit, then there's still a chance if it's the type that has legs sticking out the side at two 90-degree angles (technical term is SOIC; aka "gull-wing" package).

[egemme]

Hi guys,

Listen, I'm not a solder expert. I only had to solder a DB25 when I was at the college back in 86 and wanted to tear-off my shirt. So imagine a micro solder... But since this thing is going to dead anyway, I might give it at try. I'm not very aware of irons brand and types, nor which soldering to use to do a great job. What you recommended me so far unfortunately doesn't tell me anything clear. So I need a good guideline here. After this, I will evaluate my capacity to do the job myself or head for a certified electro-technician in my neiborhood. However, I do have a old Weller SP23 which I believe is 25W. Well you would say this is a good start since most people doesn't have one at all. I believe I might not need soldering since the surrounding solder might do the job right?

So, I unfortunately have a Hitachi (fru 11P8258) which has an opaque sheet over it. So I won't have any other choice than removing it so see how the solders look like. Tell me, does this sheet is simply glued in or what. I wouldn't like to damage the circuit by pulling on this tiny sheet of plastic or simply breaking it. Primarily, it looks like a large piece of tape.

And also, Hitachi might be a whole lot different from the models you were refering to isn'it? Do you have a clue of what I should expect under this piece of film? You'll find attached a picture of what my Hitachi looks like. This is not mine but a picture I've seen on the Web, but it is likely identical to mine.

Thank you so much for your input.

[phool@round]

Your Weller SP23 is the perfect iron for the job. A very clean tip is all you would need to reflow the existing solder. If you think you might need a spool use .381mm (.015") diameter silver-bearing solder.

Your screen is very different from mine. Does it look similar to this one? http://cgi.ebay.it/DISPLAY-HITACHI-TX36 ... dZViewItem

The opaque sheet looks to be double sided taped at the edges, primarily near the socket. If your very careful and do not over flex, bend, or mutilate the circuit board by pulling up the sheet then you'll have half the battle won. I would only lift the sheet from the socket to the area you had a positive response when touch testing.

Decide how bold you wish to be. Remember it gets very cold up there, your already bold for not moving further to the sunny south...... to oh say...Windsor.

[egemme]

You've found the perfect picture of my LCD. This is it. Will take a look.

You know the trick in Quebec is not only the cold during winter, but the heat during summer as well. We live in some kind of high difference in temperature ranging from 90 in summer down to -22 in winter. Any glass bowl would burst in these conditions.

[egemme]

Hi, it's been a while...

I finally grabbed my courage and unmounted the main LCD circuit. First deception, it was single sided with components facing down. Doh. So I gently lifted it, but you know it takes hawk's eyes to find something wrong. I should be turning presbyope in addition.

However, something caught my attention. The circuit is L shaped starting from the top right, where is the biggest part, and goes down to the bottom of the panel. On the top right edge of the panel, there is a quarter inch wide ribon attaching to a connector on the circuit. There's another, wider, on the bottom of the circuit, but this one on the top was on the one I paid more attention. By wanting to unplug it with the idea of reseating this ribbon, I found that this connector was curisouly attached with a snapping plastic cover which I doubt about its efficiency. Well I put everything back but struggled a bit with this cover. But now, I believe I understand better the behavior of the panel when I push on it. I suspect pushing on the opposite side of the circuit make it rock so it pulls on this little ribbon.

Could you tell me more about this ribbon, and tricks to secure it.

Thanks
Eric

[drtygrys]

Greetings from Eastern Europe.

May I ask how did your problem end?

I have a very similar issue with my T23. After boot-up the LCD is clear white and seems to have no response from the video chip.
External video connection works fine.
I checked the whole LCD ribbon, cleaned both connectors (on the LCD and MOBO).
I didn't try the risky part yet (pushing the video chip while power on).

I noticed something additional though. After 30 seconds from boot-up, when normally the screen goes black and "boot error" message comes up (I dismounted the hard drive) the white LCD becomes a little darker and the LCD inverter starts to buzz.

I don't know if it means that the inverter may be the cause (or one of the causes) of the "white screen" problem or it's just a side effect of the LCD malfunction?

I "just" wish to know which part to replace - MoBo, LCD or just the ribbon or LCD inverter.

Thanks in advance for any response

Daniel

[egemme]

In my case, I had the LCD panel replaced which cost me an arm. However I always kept a doubt it was repairable but despite finding a proficient microsolder, I simply chose the easy way.

You problem seems a little different from mine. In no occasion my inverter failed or made noise. I was just losing display when pushing the back of the screen at a very specific place. So I knew at all time the mobo nor the gpu was in trouble. However, you can read in this thread that the fact your external display works fine doesn't necessarily mean the gpu is entirely fine as the external port uses a different circuit path at some place.

I'm not expert, but according to my experience, I would bring your attention to two points:

1. This laptop vga ribbon has a weakness at the hinge level. A new ribbon could be found on the web for 20$ something. In my case, even replacing this ribbon didn't help

2. This inverter is responsible of bringing AC current to the fluorscent in the LCD panel. It shouldn't produce any noise. Take note that when it's failing, you don't lose the display but just the backlight. Just like old time non-retro lighted Gameboy Advanced. By chance, an inverter is not very expansive as well and even more easily replacable that the LCD cable.

[drtygrys]

You're obviously right. The inverter shouldn't be responsible for the lack of image. I think buzzing means that maybe in a short while it will need replacing too.

After reading few threads explaining the similar problem I'm still confused - which part is usually the cause of the "white screen" problem - the MoBo, the LCD or the LCD ribbon.

I think I will replace the ribbon (about 20$) and the inverter just to cut the buzzing and be sure it doesn't die in 2 months (about 30$).

If only there was a way to check if the Mobo-LCD Ribbon connector is working properly and giving the right signal. I guess it's not possible without another spare LCD to try.

Thanks for your reply
Anyone having some experience with fixing similar problem are welcome to join the discussion if you please )