sony vaio VGN-SR390 no display, how to diagnose?

has this model got built in ram as im not seeing any in the 2 slots

@tech_ni those are covered by black paper near cd drive

@harinderdivine

How much thermal paste is on the GPU that the heat sink shown in the 2nd image you posted, covers, as it seems very excessive where it overflows on the sides of the heatsink?

Hopefully it hasn't covered any components that may be around or close to the GPU.

Thermal paste is electrically conductive as well as heat conductive.

There should be only a very thin smear of the paste on the CPU & CPU and it should only cover the IC with not enough to be pushed out and then overflow the sides when the heatsink is fitted.

Does the laptop turn on, boot up etc i.e. is the fan operating, can you hear the HDD spin up, Windows start sound (if enabled) etc?

have you tried connecting an external monitor to the laptop?

@jayeff i have replaced the paste on gpu and cpu as it was years old with hard as rock, after replacing it (there was not any visible spill around the heatsink, but i can recheck)

side Green power LED is working on power up, HDD led lit up once, fan is spinning, but there is no display at all, no keyboard scroll lock etc.

@harinderdivine

regarding the thermal paste, I was only commenting on your 2nd image above where if you click on it for a close up you can see where the paste is thin where the GPU (CPU?) would make contact through the paste, but notice the amount of paste that is pushed to the sides. I was wondering if this was covering some components that are sometimes mounted close to the GPU (CPU?) on the board.

Can you get into BIOS OK?

Have you tried an external monitor? There'll be no BIOS display on an external monitor but if it boots up then once Windows loads there should be if it is a laptop display problem and not a GPU problem.