T61, 14" - serious backlight problem

[jm3]

Hi everyone.
I have got some serious problem with my T61, there is no backlight in the end, but other things seems to work properly. If I look at the screen carefully I can see Lenovo's logo, but it is very dark. On the external display the image is fine. I thought at first that faulty gpu is the reason but I have never meet it in that particular case.
I have also read some threads connected to this problem, but do not get the answer. Although a possible cause could be burned fuses, I checked them (only these around LCD connector), unfortunately seemed to be fine.

Thanks for any help.

[richk]

The 2 fuses involved are both on the top of the board next to the connector. (a big one, probably labled F7, and a small one). The other parts of the process are the bulb, which generally necessitates a screen change, the inverter, which is cheap, the lid switch, and the motherboard) The lid switch is a part of the inverter that is triggered by a little magnet in the keyboard bezel. If I had it here, I would plug in another screen to test whether the problem was in the LCD assembly or in the base. If the LCD turned out to be bad, I would try an inverter next.

[jm3]

A big one fuse is labeled as "F7" and conducts ~18,7V (rather good) and a smaller is only marked on top as "F" (I can't find its label) - conducts 3,3V. I have disassembled my other T60 and tried your suggest to replace the screen. It doesn't solve the problem - symptoms remained the same. Everything indicates that is motherboard issue...

I think, that the source of the problem could be elements, which controls when to turn on the inverter. I'm not an expert, so it is difficult to me to locate it.