IBM THinkpad T40 not charging

you need to remove the keyboard then the upper casing... if you have a modem, remove it to get more work room. you should be able to unplug the power connector off the mainboard (the wire between the power jack and the mainboard) and snap the old jack out of place. be careful not to break the board or anything while doing so, though it should not be hard to remove the jack since it is not soldered. best of luck

I concur with what Diegotech stated.

To iterate further;

1) The DC Power Jack (DC IN), may have cracked solder joint/s on the motherboard connector, (Female), where the DC Power Jack plugs in.

Resolder

2) The DC Power Jack may be broken.
Center Pin mount, and/or body of DC Power Jack, and/or Outer Shell mount.

Replace DC Power Jack.

3) Wires from the DC Power jack plug to the female connector on the motherboard, may be bad.

Replace DC Power Jack.

Two examples, of a place to buy an IBM ThinkPad T41 DC Power Jack,

1) http://www.buy.com/prod/dc-power-jack-connector-socket-for-ibm-thinkpad-t40-t41-t42-r50-r51-r52/q/sellerid/23962916/loc/101/215782035.html

2) http://www.machinaelectronics.com/store/buypart/IBM_Thinkpad_T41/DC-P001

Past this point it's a bad DC sensor on the motherboard.

Replace motherboard.

IBM ThinkPad T41 Service Manual, (Free),

http://www.tim.id.au/blog/tims-laptop-service-manuals/#toc-ibmlenovo

On this page go down to the 8th line.
The one that starts with > ThinkPad T20.

Go across, and click on > T41

Takes approximately 2 seconds to see the first page, and additional time to fully download.

Page 142 for 14.1 inch LCD screen
Page 151 for 15 inch LCD screen

(PDF file page number box at top)

You may have a problem with the input power jack. The jack itself maybe open and does not provide power to charge the battery or power the computer. The laptop must be disassembled to check and/or repair the jack. Try getting the battery charged from another similar laptop and then see if the laptop powers up - if it does, the problem is the jack. Worst case is a bad motherboard.

You should replace the battery. I wish I had a better answer, but that's pretty straight forward.

Check your Battery if it take charge. Then check if ever your laptop start without the battery.

if you think your adapter really works fine then you have a  motherboard issue.

If the the ram is the problem of your system, there should be a power on light on the system. indicating that some of the component of the system is not working correctly. But since you mentioned there is no light, it is the possibility that the problem is the motherboard itself.

Bad battery, needs to be replaced.

Maintenance manuals for both systems are on www.lenovo.com/support, under the publications section. But without looking at it, I would say no, the cables will not work.

check power ac adapter and batery if the batery is ok or charge do a test to the hard drive and memory ram loock on BIOS