What should i do? I tried to fix my xbox and still shows 3 red lights?

recently my xbox showed 3 red lights and would sometimes start up and freeze. I opened it up and cleaned and applied arctic silver to the gpu/cpu chips. I also put washers in between the motherboard and heat sinks. Now when i turn on my xbox, it doesnt even startup at all, not even the sound of a motor running or anything, just 3 red lights. I even replaced the spongy covers of the RAM chips with pennies and still nothing. Im tired of searching online because i cant find anything and xbox support told me i voided the warranty. any advice?