Power, fan at high speed, no image

Hi Community,

Got given a 2.3 GHz Core i7 (I7-3615QM) Mac Mini A1347 from a friend.

If it has had no power for a long period of time, it give the apple chime, then lights go out for a second, come back on and then fan spins at top speed. No image, nothing.

I have tried replacing the RAM to test if it was faulty = no change.

Have changed the power supply = no change

Not sure what else to try as I dont know alot about these devices.

Any assistance would be great :)