Conked display on 600E

[Chris Thorne]

Someone fell over the power connector of my 600E last week and apparently cracked the solder traces where it mates to the motherboard internally. Drat.

I opened the unit to see if I could weasel a pencil soldering iron in there. No dice, at least not without further disassembly. Ah, well, it works a bit erratically but I can soldier on for now.

Reassembled the unit and rebooted. No display. Did I say drat?

Disassembled again. I found that the keyboard speaker cable was disintegrating. Should have no effect on the display, though. Carefully inspected and reseated the display cable where it comes off of the subcard. Seemed fine.

Reboot again. No display. Drat. Must have lost the inverter or CCFL or both. I proceed to acquire an inverter and a CCFL from local sources. Replace inverter. Nothing. Plug new CCFL into new inverter and boot. Nothing again. Reboot with Fn-F7. Aha! The CCFL lights!

And then five seconds later it goes out. Drat? Huh?

I play around with this. It turns out that mixing and matching CCFLs and inverters, new and old, doesn't matter. The unit seems to be booting always with the external display enabled. Okay, with the original CCFL plugged in, I will Fn-F7 the LCD back to the foreground. That does work, in that the display lights up, shows the Thinkpad splash screen, and then shows me the first Win2K boot screen (the one which says to press F8 for options).

When Win2K progresses to the next splash screen, the display goes to barely visible dimness (the sort to be expected from a failed backlight). Reliably. At the same point in the process every time.

Baffling. I can imagine that I may possibly have two duff inverters here, but it seems very odd that both of them would go dark at exactly the same point in the Windows boot sequence.

Has anyone any insight to offer? I'm completely stuck.

[tfflivemb2]

Check the little black switch on the keyboard that acts as a sensor for whether or not the LCD is open. I can't remember the name of it right now. Chances are, the thinkpad thinks that the LCD is closed, which is why it keeps turning off after pressing the FN F7.

[Chris Thorne]

Check the little black switch on the keyboard that acts as a sensor for whether or not the LCD is open. I can't remember the name of it right now. Chances are, the thinkpad thinks that the LCD is closed, which is why it keeps turning off after pressing the FN F7.

Switch on the keyboard, hmmmmm.

There is an opening in the keyboard bezel with a microswitch underneath it. A small tab on the cover nudges the microswitch closed when the cover is shut. Would that be the item in question?

And if so, I assume that that would turn the display entirely off instead of just severely dimming it. Will experiment with it, however.

[tfflivemb2]

Yes, that is the switch. It turns off the inverter, which powers the CCFL. The display still technically works when the display is closed, it just isn't lit up.

I have had the same problem several times on 600/600Es that I have worked on, though it has been a while.

[Laptop_wizard]

If you have replaced the LCD sub-board a few times, then it is unlikely all subboards have a broken microswitch, but is possible, goto ebay and pick up a decent looking subboard and replace it again, if that dose not work, then some thing else was oviously damaged when the power cord was snapped out. Also, check the ribbon cable on the left of the board, this is unlikly as nothing should work, if this is ripped, but is still a good idea to check. take the LCD apart, check to make sure that ribbon is properly plugged in to the back of the LCD.

Hope that helps.

[Chris Thorne]

Got it. It was in fact the lid microswitch. Good thing that I was advised to check it by y'all, because I had already considered and dismissed that as a hypothesis.

It seemed odd to me (then, and still does now) that when the switch is sending a CLOSED signal, that the display does not power down 100%, only powering down the backlight. I would have thought there were further power savings to be had from shutting off the LCD in addition.

Anyway, the microswitch housing was cracked in a subtle way that was hard to see. It fell apart when I prodded it. I then pulled out an old failed subcard with a working microswitch. Eventually I will desolder that and put it on the new card. For now I put a meter on it and figured out which terminals to solder across to send OPEN at all times. Will have to manually power down from now on. Not a big deal.

Thanks for the help!

Oh, and I found my power problem too. Cracked power barrel. As the plug goes in, the crack lets the contacts inside of the barrel be pushed away from solid contact with the plug. Not sure what I am going to do, or what I can do, about that.

[tfflivemb2]

Glad that you got it!

[jsuebersax]

Could someone please tell me where the lcd microswitch is? Is it above the F2 key, to the right of the Esc key and the left of the "IBM Thinkpad" logo?

Thanks!

[tfflivemb2]

Yes, above the F2 key.

[jsuebersax]

Okay, thanks.

I lost my backlighting last week, but the lcd itself still seems okay.
It happened suddenly, without much advance warning.

The lcd/lid switch itself broke some time ago, leaving only the posts extending from the board. As I look *down* on the unit, there are three slot-like posts extending upwards. The middle post is slightly wider than the other two. So it looks basically like:

+--+
| 1 |
| 2 |
| 3 |
+--+

Which posts did you [Chris] short/connect to regain your display?
(I understand that likely you shorted these under the board).

BTW, once the plastic housing of your switch fell apart, I wonder if you even needed to short the posts. For me, in the broken condition, the default seemed to be "enable backlighting."

[jsuebersax]

Since at this point I don't think my problem is the lid microswitch, I'd like to figure out what the next step(s) should be.

Model: 600, 13.3" screen

Problem Description

1. no back light
2. LCD itself works fine (via reflected light)
3. external monitor works fine
4. rapid onset; no advance warning; no pink or dim screen before

Possible Causes

1. lid microswitch
2. inverter
3. CCFL failure
4. ribbon cable? (it has been crimped for some time)
5. others common causes?

Questions (from someone not experienced with PC repairs!)

1. Is inverter failure more common than CCFL failure? (I've read several posts and so far haven't seen an actual case where inverter swapping fixed anything.)
2. Is the inverter inside the LCD panel?
3. Could I put a meter across the ends of the CCFL and make sure its getting current? Any other obvious meter tests?

BTW, thanks for all the helpful information on the forum. I downloaded the Hardware Maintenance Manual already.

Any help would be much appreciated, as lack of my trusty Thinkpad is really getting in the way of doing my work.

[tfflivemb2]

Answers to some of your questions:

1. They are relatively equal. I have had about a 60/40 failure ratio CCFL/Inverter. The inverter, of course, is the easier/cheaper replacement.

2. The inverter is attached to the front bottom of the LCD. (See page 97 of your HMM)

3. Yes, you can check it, I am not sure though what the proper output should be.

I would recommend replacing the inverter, since it is such a cheap method and the fact that you have already had problems with yours.

[jsuebersax]

>>
1. They are relatively equal. I have had about a 60/40 failure ratio CCFL/Inverter. The inverter, of course, is the easier/cheaper replacement.
>>

Thanks.

Does replacing the inverter require any soldering?

[tfflivemb2]

Nope, just a screw driver, a thin knife blade (to remove screw covers) and a little patience.