Sony VIO

I have a Sony Vio Notebook model PCG-955A.

It will not boot. I just get a black screen. When I power it on it hits the HD a couple of times, spins up the DVD drive and floppy drive and that’s it. I’m a Dell Laptop tech so I had a look under the hood. Reseated HD, CPU and checked cables. I hooked it up to a monitor no change. I have tried different boot orders. Tried floppy and CD-ROM will not boot. I’ve tried one ram piece at a time.
If I knew for sure what part to replace I would give it a try.

Thanks