No mobo power to LCD inverter or Thinklight - any ideas?

[underclocker]

FYI, I just had five T4x mobo's returned from GPU repairs at Superior Reball, see this link for much more info --> http://forum.thinkpads.com/viewtopic.php?f=2&t=72974

Anyway, four of five seem perfect, but one won't light the LCD or Thinklight. The funny thing is that the GPU seems fine, I can see the image on the LCD and it passes the graphics tests, but no matter which LCD assembly I try, and I've tried two SXGA+ and two XGA assemblies, the backlight and Thinklight won't illuminate. It worked before the repair.

BIOS/EC is up to date and the other assemblies work on any other working machine. I am hoping someone knows where I should look, like maybe something is dirty? I have ensured that I am getting the complete connection between the mobo and LCD cable, plus I've removed and/or swapped every other part. I've even tried it with basically a bare board, memory stick, keyboard and LCD - no go.

Any suggestions. (I'm pretty sure Superior Reball will refund the cost, but I'd prefer to have the mobo working!)

[limpelephant]

I'm having the same issue with a T60. I've purchased new inverters and it's not working. I put the screen and/or inverters into other systems and they both work fine.

Edit: My thinklight works. just not the backlight on the lcd.

[xyz]

On the t60 it prob will be the fuses around the area where the lcd cable plugs into the motherboard under the black taping..
I had a similar prob and it was the 2 fuses under there around the connector..

Should be a similar scenario for the t40 too.

[limpelephant]

And this is were my super noob shines.

There are fuses where?
I see the black ribbon cable. You say there are fuses on the mainboard itself? or are they in line of the cable?

When i do a search for fuses I'm not finding what you're referring to

[poshgeordie]

Have a look at this topic in progress about the locations and types of fuses on T4x boards - whilst this doesn't show where the T60 fuses are, it does show what they look like and may give you a clue as to what to look for.

[limpelephant]

Strange thing happened this morning. I turned the laptop on and left it there. When it beeped as to notify that it had gone into a sleep mode the screen powered on.
Is it possible the wiring is backwards to the lamps?

[limpelephant]

When the laptop powers off the screen it actually powers it on. If I don't turn the computer off or put it in sleep mode I can continue to use the lcd. If i do power the machine off it requires the timer in Windows to turn the monitor off to enable power again

[poshgeordie]

I don't have any specific idea, but it sounds like a logic chip has gone wrong or is not switching as it should.

As I see it bottom line is that it's a new motherboard....

Does it act exact the same with an external monitor instead of the built in screen?

[limpelephant]

external monitor's work fine. I've replaced the inverter board and still no luck. I've tried 3 different lcd's as well.