Depending on the CPU quality you migh also need a little bit more CPU Core Voltage.
Without this test you’ll have to guess because as I mentioned before this could either bad motherboard or bad LCD screen.
You’ll have to disconnect the video cable from the LCD screen (connector 2) and the inverter board (connectors 3 and 1).
After that you connect another working screen and test video.
For this purpose I’m using one of my test LCD screens.
Few days ago I published a short article about overclocking non-K CPUs.