A customer of mine dropped off a Dell Latitude D600 notebook that runs fine using battery power but shuts off when plugged in. Short circuit maybe? The strangest part (to me) is that the battery charges when the laptop is off and plugged in. If you try to power on the laptop with it plugged in, it briefly lights up the numlock, scroll lock and caps lock LED's then shuts off. If you then unplug and power on using battery it works fine... until you plug in again which causes it to shut off immediately.
Is there some sort of electrical path that only the AC power travels on that is shorting the machine out? I am not educated enough to know how to test individual parts of the motherboard for shorts. So far all I have done is try another AC Adapter which had the sam issue. I have stripped the machine down and have physically inspected the motherboard and haven't seen anything that stands out. I can post some high resolution images if that helps.
Any help would be greatly appreciated. I hope I can help others here in the future!