TriggerFinger

With a new adapter in place, I suspect your 'replacement' motherboard may be defective. As in my previous post, test the output of the AC adapter first. Make sure it matches the laptop requirement or base it from the original adapter label. If the output voltage measures OK then for sure there is an issue with the motherboard.

A few things to check on the motherboard. Visually check the DC jack connector on the laptop side. This may have lifted off the board. Also try powering ON with ONLY keyboard, LCD and motherboard. Remove everything else (i.e. HDD, CD/DVD, WiFi, Modem, etc.). If you get to power ON without any of these devices, put them back one by one while powering ON each time.