deputy dawg wrote:Dell Latitude E7440 using our standard Windows 10 image....I eventually came across the solution in this video: https://www.youtube.com/watch?v=00xRSqyGnks (no sound)....Removing a screw underneath the keyboard fixed the problem. As soon as I did that the CPU started performing normally, and the guy who made the video claims he has fixed over 450 of these Latitudes this way with no side effects. I'm sure there is a perfectly logical explanation for this behavior, but who would have ever thought a factory-installed screw could cause such a specific issue?
Someone must have hit the infinite improbability drive, because you have landed in the portion of space where I have an autopsied E7440 carcass in the e-waste bin. Here is the area identified in the video:
My best guess is that Dell designed this unit to a target size and weight and made cost-cutting sacrifices on the physical stress analysis. For example, a lot of these E7440s have a cracked bezel at the top of the keyboard, in-line with a hidden screw mount under the keyboard that indirectly secures the bezel to the bottom pan via the hinge steel. It is near the mounts for the left screen hinge, and the bottom-pan on the left side has less structure than the right due to the cutout for the cooling fan assembly. So the pan overflexes on the left side and the plastic bezel eventually fails at that point.
Here, as you can see from the pictures, the retention spring for the battery clip attaches next to the post supporting the problem screw. There's probably another stress point there and over time it warps the motherboard slightly and causes some kind of fault, which it then relieved when the screw is removed. Top side (under the keyboard shield) has a few SMT devices close by, bottom side (by the post) is fairly clear, no meaningful damage visible. It's not obvious to me what the exact failure mechanism is, but there you go.