T30 strange backight problem

[madrigal]

Hi everybody!
I have a IBM T30 2366-PG3 with strange problem:
LCD backlight stops working from time to time without any reasonable reason. I have impression that happens when I'm carrying the laptop back and forth, but it's not always the case. The actions I take are to remove the keyboard, palm rest with keyboard bezel and LCD plastic frame. Sometimes also unplug and plug the LCD ribbon cable and inverter from both sides (ribbon cable and lamp plugs) and voila - the backlight works again for undefined time. My first impression was that ribbon cable is failed, so I purchased and obtained an used, but in good condition cable. Unfortunately after cable replacement everything was the same. Now an inverter is on the way (because these are relatively cheap parts comparing to motherboard or LCD). Oh, I've almost forgot - in one of the backlight outages I plugged the spare LCD from T20 (which I know is working) to the inverter and backlight didn't light.
So, my question is whether anybody has had the similar problem? I'm going to conclusion that something wrong has happened to motherboard (and more precisely to the motherboard LCD connector), but I just don't want that to be true.

[RealBlackStuff]

Welcome to the forum.

You say you connected the T20 backlight cable to the T30 inverter (and hopefully nothing else!), and nothing happened.
Sounds like you have a bad inverter.
Please note that T20 and T30 LCD/inverter/cable are NOT compatible!

[madrigal]

Hi, RealBlackStuff and thnaks for the hope you giving me. Replacing the inverter would be the easiest and cheapest solution. I do not want to mess with connectors resoldering, but who knows - will see when inverter arrives. One last question - is it possible to measuring the inverter's output voltage, because I didn't have success - if the LCD lamp is unplugged it seems to me that inverter's voltage is too high, but when lamp is connected and works fine any attempt to measure the voltage leads to backlight disappearing. In such a case I have to turn the laptop off and turn it on in order the lamp to light again. May be some kind of inverter's internal protection is triggered, although I don't think my multimeter's internal resistance is too low?

[RealBlackStuff]

I've never tried to measure the CCFL voltage (on the pink-white cable from inverter to LCD), too dangerous!
Be VERY careful, it's between 1100 and 1350 Volts!

[madrigal]

Yes, you are right - I learned that by hard way when accidentally touch the wires I used to measure voltage of CCFL (when the CCFL was unplugged). But I think the voltage is so high only in the moment of CCFL ignition. After that the voltage should go down to the rate enough for supporting fluorsescent discharge.

[madrigal]

Finally solved the problem
As rkawakami said in other forum's topic http://forum.thinkpads.com/viewtopic.php?f=2&t=76764 the problem turns out to be stuck lid switch. Now everything works fine and I have spare ribbon cable and inverter
So, the moral is: before going to buy parts for replace, check the more obvious reasons (some kind of Occam's razor).