I have a T-60 which is past it's lease life and must be returned with a dozen others. It has to work to be returned, otherwise we're paying some annoying bucks for it.
I have replaced the motherboard, inverter, LCD monitor, and keyboard.
The LCD monitor fades out in a few minutes only while under AC power
An additional desktop monitor will stay on if connected.
If under battery power, the LCD will stay on.
If I FN-F7 a few times, it will cycle between monitors and the LCD will come on...shortly to fade out...to the point where the display can be barely seen. That takes a minute or less to happen. Never any problems with the second monitor. While under AC power, the LCD exhibits mild flickers before it dies out - the secondary monitor is always solid.
I have tried different power cubes. I have tried it in a docking station.
Behavior is the same.