Dell optiplex wont start

[luciaki95]

I bought i new power supply for my dell optiplex 780 but it wont start. It only brinking amber light number 3 what could be the problem. Please help

 

[hang-the-9]

Could be a dead motherboard also, are there any beeps? Try removing the RAM, if it does not beep, it's probably a bad motherboard.