you most likely need to reflow the graphics chip if you remove the ram chips off and don't hear a beep usually the cause is hairline cracks in the BGA all you need is a heat gun some no clean flux and a ir thermometer.
1. clean all the thermal paste from the gpu chip make sure you don't let any of the paste run into or around the corners or you're screwed.
2. apply the no clean flux to one side of the chip and tilt it vertically till you see the flux come out the other side do this to atleast two sides.
3. slowly apply heat to the chip in a swirling motion (dont keep it centered on the chip or you will fry you're gpu).
4. once you reach 380 degrees Fahrenheit stop and let it cool for 15-20 min.
5. Make sure you don't move it at all while it cools down or you might make a solider bridge in the bga and its game over.
also make sure the motherboard is balanced out flat when you reflow it.If you hear beeps after you reflow it(with no ram in the slots) than you successfully reflowed you're gpu
hope this helps