600X Blank Screen after cable shredding

[ururk]

Hi all...

Very new to the forums. I am in the process of fixing a 600X, and am a bit stuck.

A friend gave me their 600X to fix - he had tried to convert it to a digital picture frame, but had not been able to properly take the screen apart - the hinge covers were cracked off, and the metal hinges were bent. The screen was cracked. I'm thinking "brute force" method.

OK, so I tell him, order a screen on eBay, send him a few links. He got one, with a 30 Day warranty, for a "good price". However, when I go to attach it, I find that he had partially cut the ribbon cable to the LCD! Not the inverter cable (though it had some indents in it from ?something?. So I ordered a cable set on eBay seller that said it works...

Nothing. The LCD does not come on, the backlight does not come on. Machine boots, external monitor works.

So I reseated the card between the motherboard and keyboard/speaker/inverter cable. Didn't work. I noticed there was a strange dust on some of the contacts on the bottom of the card, but it wiped off w/out hassle.

So... what next? Or, at this point is it a lost cause? Should I send the LCD back for exchange to the eBay seller? Should I send the cables back for exchange? Neither operate - no backlight, no LCD display.

He did say it worked before (until the screen cracked).

Any help would be appreciated!

Thanks!

[rkawakami]

Welcome to thinkpads.com!

Checklist for LCD problems:

1) If you are booting the system with an external monitor already attached to the system, once Windows has loaded (verified via said external monitor), try the "Fn+F7" keystroke combination several times to switch the active monitor from external to internal (LCD). Your panel may actually be working but not active. There are three possible settings using this key sequence: a) LCD only, b) external only, c) both LCD and external.

2) If you go through all three possible combinations of monitor settings with Fn+F7 and you do not see ANY backlight come on the LCD, then look very closely at the LCD panel in each one of the three possible monitor settings by shining a strong flashlight on the panel at an angle. If at any time you see a "ghostly" image that means that the ribbon cable from the Sub Card (thin board with the lid closure switch and microphone) to the back of the LCD panel is working properly and that your real problem is the lack of a backlight.

3) Assuming the backlight is not coming on, there are four possibilities: a) bad connection of the Sub Card and/or plug going to the backlight, b) bad inverter card, c) bad CCFL (backlight) in the LCD panel, d) lack of proper signal/voltage from the motherboard. These are arranged in increasing order of cost to repair. Since the LCD panel has been changed out and your friend says that his old panel worked, I would suspect that the new panel has a bad light. Even so, double check all of the connections from the motherboard, to the Sub Card, to the inverter.

[ururk]

I did all these steps (should have mentioned).

I took the Sub Card off, inspected the contacts, they looked good. Reseasted it, and all associated cables twice (LCD, inverter cables) on both ends. Tried the "undamaged" inverter cable. No go.

Could the cut ribbon cable have damaged the chip that runs the LCD (on the motherboard end)? The external display worked, are they not the same chip? Is there anything that could get dislodged if someone was mishandling it when they tried to disassemble it? I know some laptops have video cards that are not part of the motherboard.

One peculiar thing - I never asked him about this - but the trackpoint does not work.

And, I do not have a known working machine to dissect and test with my parts, which is the nail-in-the-coffin for testing the parts bought off eBay.

[ururk]

Also... VGA is analog, while LCDs are driven with digital signals. But I would *imagine* that the path would be something like:


Digital output---->LCD or Digital to analog converter (D/A)
D/A----> VGA port


So if the on-board graphics chip was fried, then the external display shouldn't work, right?

[rkawakami]

The 600X has the video on the motherboard; no separate "card" that can be replaced. I would imagine that you are correct with your analysis of the video circuit concerning analog vs. digital and the D/A converters. No known schematics are available so troubleshooting is basically what you have described: swapping components out with "known good units".

I doubt that simply cutting the cable could have damaged anything on the motherboard, unless it was cut while the laptop was powered up.

Try the flashlight trick I mentioned earlier. It could shed some light, pun intended , on the nature of your problem. If you are using (assumed) good LCD panel and ribbon cables and you still don't see any pixel activity, then I would suspect the motherboard. If, on the other hand, you can see an image on the LCD but no backlight, then I would think your inverter is non-functional or the backlight in the supposedly good LCD panel is defective.