Lenovo thinkpad w700 was used more than 3 years. last week, inverter was not working. I checked it by multimeter: power input was ok but no power output. Video cable and backlight were working well. I purchased a new inverter from IBM parts center, installed and then problem solved.
But after a few days, the problem came back, checked by multimeter, the new one was broken again. I checked the inverter board, and found ohm of a pair of small capacitors was zero (very quickly to zero and meter never changes). It seems the capacitors were damaged. The two boards have same capacitor problem. This pair of samll capacitors are located just on top of the coil. Video cable and backlight have no problem.
I don't know if it is the capacitors making the inverter malfunction? something must be wrong making the board broken again, and why? Please anyone can help me to solve this problem. Thanks.
p.s. In most time this w700 uses external monitor only, and sometimes uses both screens.
Thanks for your reply. The problem solved! The "broken" problem was due to a fault power management plan which always turn off LCD backlight of laptop. After I switched back to default plan (Thinkpad plan), everything is fine. I hope my experience would be helpful for others who have similar problem: checking your power plan first!