I am having the same issue, figured it was an overheating issue, so I took out the fan and it was plugged solid. Cleaned it all out but it still wouldn't even get to POST. I then was feeling the heat sink on the video chip and while pressing on it, the laptop started and booted up until I released the pressure on the chip. I bought some thermal paste and redid that chip and found that it actuall wasn't the problem. Tracked it over to the fan connection on the MB. If I hold down that connector, it starts up but as soon as I release it, the laptop shuts off. I am waiting for a local PC store to open to either purchase a new fan or get the conector re-crimped. Will try to let you know my results, hopefully this is it, otherwise its my MB and thats not worth replacing.
UNFORTUNATELY your laptop has broken mainboard bridge(small chip on board)there is nothing to do with that ..you can change mainboard or sell laptop on ebay as faulty and buy new one.