HP 1620n will not power on at all

I have a 1620n that had been working fine. When I tried to start it last night, it would not power up at all, no fans, nothing. The green light on the back of the power supply was on solid. Checked the button for current, and it works. It uses a D3057F3R power supply. Power cord checks out. Would this be a power supply problem or motherboard problem, or how can I troubleshoot to determine which?