Dell Studio No Post

I recieved the Dell Studio 1909 from a client as a partial post it would display temporarily and stop posting. I replaced the Power supply on this system 5 months ago first I replaced the LCD inverter it did not do anything next I thought the mobo was the issue maybe the GPU was dying I ordered a new refurbished one now It won’t display at all and the fans scream full blast. I replaced the cmos,CPU, Ram and all the little 3 pin cmos plugs thinking bad PSU or maybe a different mobo