I recently replaced my FW13 Intel mobo with the AMD 7840U.
I had problems with the first AMD board (it would just shut off and not start until I re-plugged the battery, among other things).
They replaced it and it worked mostly ok for a while, then occasionally would shut down and I would have to re-plug the battery to get it to start again or even charge.
I reported this, they asked me for photos. I went to take photos this morning, and just for good measure tried to start it up again. No doce.
After lifting the kb/cover, I noticed some dust, which was odd (my two FW laptops have been eminently clean after much use!), and which I hadn’t noticed before. It was where the storage goes (which was already removed), and while I would likely have seen it previously, I just assumed I’d been distracted or something when I had removed the storage last week.
I started to remove stickers to get pictures of the board, and a whisp of smoke came up from that area!!! I quickly unplugged the battery, and it stopped.
Here are some photos, you can really see the burned area.
Anybody else have this issue? I’m beginning to wonder if there isn’t a design flaw with this board…two of the same board not working, one of them burning. I hope it’s just a freak incident, I just want a working AMD board for my 13.
Most AMD boards obviously work fine. Mine does for example. Unless you treat the board very badly for some reason (like if you have metal dust in the area or you operate on the board when it’s turned on), I would just get it replaced again by sending these pictures to support.
Perhaps you could add your pictures to your post, to make it easier for others to view. Just dragging-and-dropping an image should upload automatically. But there is also an upload button in case you’re on mobile.
There is a burn mark on one chip, correct? It has PUZ4 marked on the mainboard just above the chip. And it looks like the burn has also distorted the surface of the chip, making it no longer flat, yes?
Perhaps you could get a picture of the markings on one of the other PUZ# chips above it, or read them out? I can’t quite make it out. Think I can see “1171” on the last full line of the burned chip, & the PUZ3 chip seems to share that.
Any idea what may have caused this? Apart from the obvious shorting by debris possiblity (very remote, I’m very careful to keep things neat when opening a laptop or computer).
Sorry, I meant all of the markings. I can’t for certain make out any of them. The last line is usually the least important, least useful for identifying a part, I only mentioned that line because that’s all that was visible on the burned chip.
By just looking, all you can really do is make guesses. And the fault may not even be related to the chip that burned. The chip just being the place where it showed itself. Even with testing the board and chips, it can sometimes be hard to know from certain. Did they want the board back?
PUZ4 is one phase of a three phase buck converter which takes in the battery voltage to generate the VDDCR_VDD rail. See the bottom center block on page 2:
It uses a MP86901 buck converter IC. I can’t find any details on the exact IC because it is a limited availability part (e.g. only available with direct contract with the manufacturer, typically involving NDA)
The IC’s low side FET likely shorted and caused trace damage. Not sure if its a controller issue or design issue
Given this image from one of monolithic powers’ presentations, its just a half bridge power stage that takes an external PWM.
I work with similar electronics. It could be a bad batch of ICs, or some weird edge case that didn’t show up in earlier batches or validation testing. Could also be a software issue w/ how the firmware configures the buck converters. Additionally, the schematic says that each are capable of ~35A but the part is only rated to 30A. Even then, this kind of component ideally needs top side thermal heat-sinking for those kinds of currents.
ETA: Later in the schematic it mentions the MP86941 - inconsistent but the part itself has the same rating according to the MP slides.
