600X Screen Problems

[emmett]

Hi,

I have a dual-boot 600X and the screen has begun to play up. It started a couple of weeks ago when the screen started to flicker a bit and go a bit dark. The screen then came back to normal.

Now the screen lights up for a second and then goes dark. The display on the screen, however, is faintly visible. An external monitor works fine and the problem is the same with both Ubuntu, my main OS, and W98 (the 'just-in-case' stuff I never use).

I have read, on these forums, of two possible causes:

1. The display closure switch.
2. The inverter.

The inverter isn't expensive and replacing it doesn't look too difficult but before I go out and buy a replacement can anybody help by:

1. Confirming the likely diagnosis; and,
2. Advising me how I can test the display closure switch and or the inverter.

I'd appreciate any help given.

Thanks

Emmett

[tomh009]

I have read, on these forums, of two possible causes:

1. The display closure switch.
2. The inverter.

The inverter isn't expensive and replacing it doesn't look too difficult but before I go out and buy a replacement can anybody help by:

1. Confirming the likely diagnosis; and,
2. Advising me how I can test the display closure switch and or the inverter.

Third option is the backlight itself -- usually this would manifest itself with a reddish tinge in the backlight before it turns white (or shuts off, now). If you see the image on the screen, I think it's not the switch (though I could be wrong as I'm not familiar with this particular problem).

If you haven't seen the red/pink tint, either, the inverter is a very likely cause. And fortunately an inexpensive repair ...

[emmett]

Tom,

Thanks for the feedback. There has been no problems with red or any other colour or tints just the screen going very dark or virtually blank.

It does however sometimes come back to normal for a few seconds or even a few minutes before going dark again. Is this consistent with a fault in the inverter?


Emmett

[rkawakami]

The inverter isn't expensive and replacing it doesn't look too difficult but before I go out and buy a replacement can anybody help by:

1. Confirming the likely diagnosis; and,
2. Advising me how I can test the display closure switch and or the inverter.

As tomh009 says, the problem could also be the backlight inside the LCD panel. Also, in addition to the lid closure switch and inverter, the problem could also be on the motherboard. From your descriptions, it sounds like it's related to the inverter (ghostly image still on the screen, flickering). You might try opening up the laptop and re-seating the following connections:

Connector going to the backlight from the "right" end of the inverter card (inside bottom part of the LCD/lid assembly)
Connector/ribbon cable assembly at the "left" side of the inverter that goes to the Sub Card
Sub Card (this is the small, thin board that also contains the lid switch)

If re-seating these connections does not seem to help, then I would start with replacing the inverter board.

As far as testing the lid switch and/or the inverter, it is possible if you have a multimeter that measures ~1000VAC and resistance. The inverter should generate several hundred volts AC if operating correctly. The problem is getting the meter's leads attached to the inverter's output without: 1) shorting the leads together and 2) not shocking yourself. I don't know exactly what the voltage is for a properly operating inverter; I've never tried to measure one.

The lid switch can easily be tested with a meter's continuity/resistance function. You can refer to my site on the Sub Card/lid switch:

http://www.rkawakami.net/ibm_600x/sub_card/

The pictures of the two switches (near the middle of the page) shows the three terminals of the switch. This type of switch is called SPDT (single pole, double throw). It has one common terminal and one terminal which is "normally-closed" and the third terminal "normally-open". From left to right in my picture, the terminals are "normally-closed", "common", "normally-open". With the Sub Card removed from the laptop, if you connect one lead from the meter to the "common" terminal and the other to the "normally-closed" terminal, you should read 0 ohms. Leaving the "common" lead connected, move the other meter lead to the "normally-open" terminal and you should read "open" or something that is NOT 0 ohms. If you then move the switch lever down, you should read 0 ohms.

[emmett]

Ray,

Thanks for your help. I'll take the machine apart over the next few days and see if I can get to the root of the problem.

Emmett

[emmett]

Coming back on this question...at last.

I finally got hold of two replacement inverters and installed them onto the Thinkpad. The Thinkpad worked fine for about ten minutes and then the problem reoccured. This happened with both replacement inverters.

I have fiddled with the connections and the only thing that works for a moment is when the left hand ribbon is connected up. At that point the screen comes on for a moment and then goes off again. Opening or closing the screen doesn't seem to make any difference . I have checked that all connections are properly seated and I have made sure that all the screws are properly tightened.

I have also fiddled with the lid switch with no effect.

Can anybody suggest potential fixes for the problem or am I going to just have to replace the LCD unit totally?

I'd appreciate any comments or suggestions.

Emmett

[rkawakami]

It seems like you have reduced the potential problem areas to two:

1) The LCD panel (well, actually the backlight inside the panel)
2) Motherboard

At this stage, the next step I would suggest is to swap out the entire lid (LCD panel, cables, inverter) or if you don't mind doing a liitle more work, just the LCD panel, with a known good unit. Easy to say when you have spare equipment laying around . You are getting to the point where you are going to be spending more money than what the laptop is probably worth.

[emmett]

Ray,

Thanks for the prompt reply. Unfortunately I don't have another LCD lying around so I'm going to have to decide whether I buy a new LCD or send the laptop to a repair shop that, hopefully, has one that they can test the machine with. I'll probably go down the latter path.

Emmett