My latitude 100L making same problems, it works from battery, but not from AC-adapter. Adapter is OK, problem is on the motherboard, I checked with oscilloscope - PWM controller (ISL 6247) on the motherboard give power for short time and for unknown reason, interrupt supply of power. So, I will play a bit again with this laptop, and if it will not work I will probably replace motherboard. Check on ebay, it could cost around 40$.