Disclaimer: Three blinking red leds indicate General Hardware Failure. There are several possible reasons to see this error, but this post only covers the one cause that is almost always at fault.

Why the 360 breaks:



I assume that most people have seen photos of the 360 motherboard. It has two large x-clamps on the bottom that hold the heat sinks on tightly:











These clamps look harmless at first glance, one would never suspect what these horrible little pieces of evil hardware would be capable of. But, let's take a closer look at the design of the x-clamp. It has a hook on each corner to lock onto the heat sink, but it gets its tension by pressing up into the motherboard. Have a look at the side view:











You can see that to pull the four corners up to the motherboard, it puts considerable pressure up on the motherboard... and directly underneath the center of the gpu and cpu. This does provide an excellent, even pressure for holding the heat sinks onto the chips but the design failed to consider the high temperatures generated by the 360's chips.



When the 360 chips get nice and toasty hot, the board underneath gets a bit soft from the heat. A combination of the softened motherboard and the x-clamp pressing up firmly from underneath can cause the board to warp. Once the board warps up underneath a chip (most often the gpu) this can cause an edge of the chip to lift off the pads on the board. It doesn't take a genius to figure out that the gpu or the cpu will not work if some of it's connections have pulled off the board. This is the actual cause for the three red flashing leds, which is the 360's error code for "General Hardware Failure".



Here is my neat little "before" diagram showing how the x-clamp holds the heat sink in place:









Here is my neat little "after" diagram showing the warped board, the evil x-clamp, and the lifted gpu:









So, now we have a solid understanding of how one bad choice of a small part has caused so many millions (billions?) of dollars worth of repairs, and so much pain and misery for so many gamers. The good news is, once the problem has been identified, a fix for the issue can be devised.





Reversing the damage:



Now that our diagram 360 has warped its board and lifted the edge of the gpu off the motherboard, we have the Red Ring of Death flashing on the front. It's dead to the world, and needs a couple weeks (months?) vacation in the Microsoft workshop to be repaired. That's great, but quite a few of us (thousands) have managed to void our warranties for one reason or another. What are we to do?



Well, the tutorial I used to fix mine is right here. I won't be showing the whole tutorial here (his was good enough for me, it should be good enough for you) but I'd like to explain the concept of how and why this fix works.



The basic idea in steps is:



1. Remove the x-clamps and heat sinks.

2. Clean the old thermal paste off the heat sinks and gpu/cpu.

3. Unscrew the heat sink posts from the heat sinks.

4. Enlarge the holes in the metal casing under the eight sink posts.

5. Replace the thermal paste.

6. Use 5mm machine screws with a stack of washers to bolt the heat sinks down to the metal case without the x-clamp.



Ok, so all we need to do is enlarge some holes, and replace the posts and x-clamp with some screws and washers? Yep, that'll do it. Huh? Sounds too easy, how is that going to help?



Well, the screws pull the heat sinks down firmly from the four corners, but there is nothing pushing up in the center anymore. This pulls the chips down flat onto the motherboard, and after it gets hot it also forces the warped board to flatten out again. Once the chip is flat on the board, the connections touch back down on their pads, and the chip can function properly again. It's a pretty simple problem, and a pretty simple fix... but it works!



Let's give our diagram 360 the "X-Clamp Replacement" fix and see the end of those pesky three red leds:









As you can see, once the gpu chip has been pulled back into place, everything can run normally. From the poll results, this x-clamp replacement appears to fix the Red Ring of Death at least 90% of the time. I'm not sure if anyone has any good answers for the other 10%, but the odds definately make this worth a try if your warranty is void and your 360 is giving you the three evil eyes...

Credit for the X-Clamp Replacement go to RBJTech and many others from the community who have contributed ideas, discoveries, and feedback. I have only compiled this work into an easy to follow explanation.