Hi Trying without success to fix a friends Dell 1546 laptop however am pretty sure its the main board that has gone ! symptoms : switches on ok but no splash screen no bios detail etc screen just blank (tried external vga as well no display ) fan starts up for a few seconds power light goes off after 10 seconds attempted the following stripped down to main board then re-seated processor removed bios battery left out over night then fitted new one re thermal pasted processor I suspect failure of mainboard probably GPU as no display hence shutdown after 10 seconds, with fan starting up I guess cpu ok as instruction given to start fan then shutdown system due to hardware failure , no video output? I guess probably not economical to repair as a new board too costly.
Did you try reseating the RAM? Otherwise, sounds like you should try reflowing the motherboard. To reflow it, you'll want to strip any detachable parts off, scrape off any stickers, etc. that you can, prop it on a cookie sheet using tinfoil (meaning no metallic part of the board should touch anything, so use the tinfoil to raise it up), and bake it at about 385F for about 8 ish minutes. It sounds ridiculous, and it is definitely a last resort, but I've seen it work.
yes re seated ram , baking it sounds a bit drastic ! found a company in london who say can fix the board to component level will possibly give it a try ??
reball is the proper way.. however u could have used a $20 heat gun to resolder it yourself for 3 minutes time.