As stated, my HP Pavilion G4-1318dx will turn on, but the screen stays black, not off, black. The f12 key does have its amber light on, and the power light is on. However, I am looking to find a way to know for sure if the CPU is out or if it is the main board, I have done every option that does not involve replacing parts. This includes taking apart the laptop to the bare minimums and running it without success. So, my question is if there is a way to know for sure what the error is or what hardware is defective. Ask if you need anymore information and I'll be glad to answer. Thank you!
However, I really do like this laptop because, like you assumed correctly, it has a removable CPU, and almost everything else in the laptop is modular! However, if there is no way to test it, then I guess I'll just have to let it sit until I find a replacement part! Yet, if there ever is another way to test it, I hope I find it! 
