YouTuber Buildzoid from Actually Hardcore Overclocking believes he has figured out the root cause behind a recent spate of Asus Z690 Hero motherboard failures. If true, the issue is related to a single capacitor on the mainboard being installed backward at the factory.
Reports of the Z690 Hero failures began around 10 days ago when @TheMaxXHD, @Duhjahno took to Reddit and the ROG forums (opens in new tab) to complain about their Z690 motherboards no longer booting. Other users also shared images of their motherboards, revealing a commonality between the failures: two burned-up MOSFETs near the Q-code reader and DIMM slots.
However, from what we're able to discern, not all Z690 Hero motherboards suffer from the issues. YouTuber JayzTwoCents notes he has used his Z690 Hero extensively for testing purposes and it has worked perfectly fine with no failures.
Buildzoidhas a theory as to why some Z690 Hero motherboards are dying and others are not: Pictures of the impacted Hero boards have two burned-out MOSFETs in between the Q code reader and DIMM slots to the very top right of the motherboard.
Those MOSFETs are responsible for providing 5V power to a number of components on the motherboard, including the power delivery system for the DDR5 modules. This is interesting because users that have the board failures report that the Q-Code reader spits out the number 53 when boot up fails. Code 50-53 for the Asus Z690 Hero indicates that memory initialization has failed. Presumably, this is the only reason why the board fails to boot.
From this info, one can conclude that the MOSFETs are dying because Asus either got a bad batch or because they are cheaply made components. However, Buildzoid believes the issue is not related to the MOSFETs, but rather the capacitor right next to the MOSFETs that assists them.
If you look closely at the image above, you can see the capacitor appears to have been installed backward. Of course, the backward text is a big giveaway, but Buildzoid notes that you can see the polarity stripe on the capacitor as well, which ultimately dictates if the capacitor is backward or not.
Having this specific capacitor backward on the Z690 Hero is bad — this capacitor is polarized, meaning it has a negative and positive connection. When backward, the capacitor causes the MOSFETs to get extremely hot, and could very well cause them to melt.
For now, this is a working theory from Buildzoid and shouldn't be taken as fact. He says there's a chance Asus has another revision of the Z690 Hero where the capacitor is meant to be backward, but his educated guess seems plausible. Ultimately, the evidence for Buildzoid's theory is convincing because the image of every single dead Z690 Hero online appears to have this capacitor backward.
We'll have to wait for an official statement from Asus to see if Buildzoid's theory is ultimately correct. We've reached out to Asus and will update when we learn more.