Hi all,

Tested an SL500 and found that the backlight and LCD are ok, Invertor is good but I do not have any power getting to the invertor. Does this model have a lid switch that turns off the backlight when you close the lid? or could this be something more nasty.

Cheers

Troy

G'day and welcome to thinkpads.com!

Not sure where the lid switch is positioned and what type of technology is used on the SL500 (younger daughter currently has one in her possession) but that could be a source of your problem. There could also be a blown fuse on the motherboard. These two things are based upon how previous Thinkpads were designed.

The older systems (before the '60 series) used a mechanical microswitch mounted on the motherboard (or sub-card), typically activated by a plunger/post located somewhere near the back edge of the keyboard bezel. There would be a matching "nub" of plastic located on the LCD bezel which will push down upon the switch when the lid is closed. Newer Thinkpad systems will use a switch controlled by a magnet (a Hall-effect switch). That switch could either be mounted in the lid assembly (usually on the inverter board itself) or in the base. The magnet would be in the opposite location. So, if you don't see any obvious signs of a mechanical switch, try dangling a small steel chain across the bottom edge of the LCD bezel and along the back edge of the keyboard bezel and see if it sticks. If it does, that will tell you there's a magnet there but not really say anything about the correct functioning of the Hall-effect switch. Since the switch is supposed to turn "off" (cut power to the inverter) only in the presence of a magnetic field, I would guess that it would not fail such that it's always "off".

It's known for many of the older systems to have a fuse on the motherboard which protects the power going to the inverter. They are usually located on the board near the connector for the LCD ribbon cable. You would need an ohmmeter to check it and the Hardware Maintenance Manual for the procedure to tear down the system:

http://www-307.ibm.com/pc/support/site. ... 69929.html

Thanks for the information. I have looked over this board and not being an electronics expert cannot identify the fuse if any.

Any pointers?

Here's a couple of pictures of a T23 motherboard that shows fuses: (they are outlined in blue)

http://www.kawakami-ca.com/ibm_t2x/main_fuses.jpg
http://www.kawakami-ca.com/ibm_t2x/let.jpg

The fuse for the inverter is usually like the tiny ones in the let.jpg photo that are marked with an "N" (sideways they appear to be "Z"), just below the long white (LCD) connector. Fuses are named on the motherboard starting with "F" (F1, F2, F4, F10, F11). The SL500 probably uses similar fuses to the T23.

Thanks for the images.

I tell you the fuses are small. I think I need a bigger magnifying glass

No guess on where the Hall Effect Switch may be?

FOUND IT!!

Left side of the top cover. It is part of the media panel that has the Mute, Volume up and Down as well as the IBM Help Blue button. Magnet is on the left inside of the lid, very small.

Found that the card has a faulty cable and after replacing, or should I say making a new one it worked.

This is one for the knowledgebase for sure.

trcbit...

It sounds like you have found the same issue that I currently have. The screen is black but I can see faint images when booted up. I've replaced backlight, inverter, entire LCD and no luck. I was about to throw it in the trash!!!!

Can you give me more details on what you replaced and where you found it??? I'm desparate to get this fixed for my daughter. Laptop is only 18 months old and can't afford a new one.

Thanks!!!

I have an SL500 like this. It uses planar FRU 42W8208 & the LCD has the odd ribbon connection. The "P" fuse is on the bottom of the board and tests good.

Hi there,
I have a W500 with an exact same issue. Black dim screen -- inverter is fine, LCD is fine. Please email some details on which cable you replaced and how to go about it. Thanks.