Thinkpad T40
Customer arrives with IBM Thinkpad T40 stating that it will work from a charged battery. But it will not work with known good AC Adapter. Problem: Works on battery, will not work on AC Adapter The problem is caused by 2 things in this case. First the Toshiba TPC8014 MOSFET was reading bad when I checked it with a meter. After I replaced it, the unit was only supplying 10.4v to the charge section of the board. Which is not enough to trigger the adjacent mosfet to supply power to the charge section. So then; checking the Fuse [F2] found that it was blown (open circuit), most likely by the MOSFET being shorted. click on picture to see larger view Solution: Replace MOSFET TPC8014, replace fuse. The MOSFET: 30V N-Channel MOSFET ~11a max rating Exact Replacement: Toshiba TPC8014 comment: The funniest wording of what happens under constant use. Using continuously under heavy loads (e.g. the application of high temperature/current/voltage and the significant change in temperature, etc.) ma...