ThinkPad 380XD doesn't start up

[RigoLigo]

I purchased this 380XD recently, however its power management system seems to be misbehaving. I can't shut it down either by powrr button or Windows shutdown command, but only the blue pushbutton on thw bottom worked.

Today this laptop stopped working completely. When I plug in the cord, it starts humming(very high frequency and very faint, inside the keyboard side) and pushing the power button could illuminate some status leds less than half a second, and everything was off again. I unplugged the cmos battery and ram stick. It worked for a while.but eventually the system.is dead again with the same behavior.

What's possibly wrong with the motherboard? How can is fix this computer?

[Screamer]

That sounds like the DC-to-DC converter daughterboard is defective, but I can't be sure.

Does it still produce the high frequency noises without the battery installed, when it is powered on? If it does, that means the DC-to-DC converter daughterboard is defective. Try to get a replacement (FRU: 05K3195), see if that changes anything.