Laptop powers on then shuts off after 1 second

[Jsmith2211]

Hello.

 

My mother's Novatech A15a laptop just decided to die. It was left for a week unplugged and then when she tried to turn it on nothing happened. Left it charging... still nothing. I then replaced the motherboard, and it has some signs of life now. The charging light comes on when you plug it in, and the power light comes on for about a second when you press the power button, just to die again. The fan gives a slight jolt every time it goes through this cycle. I have tried re-seating the single stick of ram in both slots, replacing CMOS battery and booting without HDD or RAM installed. What do you recommend I try next? 

 

Thanks in advance

 

James