Finally, I had the chance to test this motherboard with a spare CPU (i3-4160) but it's behaving the same. I did a quick test yesterday morning and I wasn't even able to reach the display glitches anymore, only power cycles. Looks like the situation is getting worser and worser. We can assume it's 100% motherboard's fault, but what should I do next? Is there anything I can check or measure on the board or should I go for a PCH reflow? I only have a hot air station so the best I can do is try to send hot air for a while to the PCH.

Yep, multiple times! I also measured all the possible voltages and current I learned by watching YouTube videos about troubleshooting H81 boards and I think everything looks good as soon as the board doesn't tell the PSU to turn everything off and back on and repeat the process over and over again. I read somewhere that it could also be related to faulty caps near the CPU, I measured the ESR and it looks good, I also took a picture of the square wave straight outta the VRMs

[url=https://ibb.co/QfJQF9d][/url]

Unfortunately, I don't have another CPU with the same socket,...

I already tried with a different power supply: mine is a picoPSU, tested with a 1000W 80 plus bronze Cooler Master ATX and it behaves the same. I also tried with four more sticks of RAM, with two of them (I'm not quite sure they work) the beep sequence and frequency change (four short and sad beeps - which is different from the sound I hear when I put zero sticks) but if I put two different sticks, it does the same as the actual ones. Tried also with multiple combinations of sticks in different slots, and it behaves the same.

Hello everyone! This is my first post and this motherboard is driving me crazy because everything looks so non-trivial that I don't know where to start investigating. During these days I believe I watched half of the YouTube videos trying to understand how to troubleshoot power cycles but at the same time, I'm confused because my motherboard doesn't always do that and sometimes completes the POST for a few seconds: the right amount of time to freeze, show glitches on the screen, and then reset itself.

Let me give you a bit more context to understand why and how we got here.
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Hello everyone! I'm a 29yo software engineer with a passion for electronics. I started playing around with components when I was 5, then I met computers and decided to become a programmer. In my spare time, I fixed PCs and components for friends and parents, and I also practiced overclock.
In the last days, I started deep diving into motherboard and PCB repairs: back in the days what I mostly did with computers was replacing faulty elements without inspecting them deeply. Even though I have a basic knowledge of electronics (I know the theory) and soldering (I am more of an Arduino guy tbh),...