Question Unexpected PC shut down (several attempts to fix)

[d_nussbaum]

Back in 2016 I built my first computer and it worked without issue until just recently. I noticed that it would randomly be off when I came back to work on it, and would not power up unless I removed the power cord for a few seconds. Sometimes the computer would shut off while working on a spreadsheet, or while using Chrome. (That is about the extent of my use) When powering the pc back on, there has not been a single instance where the computer acknowledges having shut off improperly. It boots as if nothing happened.

Build:
Intel Boxed Core I7-6700K 4.00 GHz 8M Processor Cache 4 LGA 1151 BX80662I76700K
Samsung 850 EVO 1 TB 2.5-Inch SATA III Internal SSD (MZ-75E1T0B/AM)
Corsair Hydro Series H80i v2 Extreme Performance Liquid CPU Cooler CW-9060024-WW, Black
SilverStone Technology 450W SFX Form Factor 80 PLUS GOLD Full Modular Power Supply with +12V single rail, Active PFC (ST45SF-G)
Gigabyte LGA1151 Intel Z170 Mini-ITX DDR4 Motherboard GA-Z170N-WIFI
Corsair Dominator Platinum Series 16GB DDR4 DRAM 3000MHz C15 Memory Kit for Systems 3000 MT/s CMD16GX4M2B3000C15

Initially, I thought it was dust build up. So I disassembled and cleaned it up. It helped for a little while, but began to turn off again as it had. So I started to believe it was a PSU failure. I bought a new one, installed it, and when I fired it up after a few minutes the pc would shut off like it was suddenly unplugged. I purchased the Thermaltake Smart 700W 80+ White Certified PSU , but since it did not make any difference I returned it.

I noticed that a fan was not spinning properly, and that my USB ports were acting strange as if they were not connecting to the motherboard.
Now I began to think maybe the computer was overheating due to motherboard malfunction. I monitored the heat and did notice sudden spikes in temperature on the CPU. Hard to thoroughly monitor as the computer shut off quite often at this point. So I decided to swap the motherboard and CPU.

Replacements:
AMD Ryzen 5 3400G 4-core, 8-Thread Unlocked Desktop Processor with Radeon RX Graphics
Gigabyte X570 I AORUS Pro WiFi (AMD Ryzen 3000/X570/Mini-Itx/PCIe4.0/DDR4/USB 3.1/Realtek ALC1220-Vb/DisplayPort 1.4/2xHDMI 2.0B/RGB Fusion 2.0/Gaming Motherboard)

Now, after having rebuilt with the new mobo and AMD cpu, it seemed fine until it started shutting off again! I found that when the computer goes into sleep mode, it turns off as well. I plugged an external hard drive in to back up the computer and noticed that the blue LED (bright normally) glows very dim when this happens as if it is not receiving enough power in the sleep state. But the pc also still turns off during relatively light use. If I let the computer run without using it, and set sleep, hibernate etc. to NEVER, it stays on without issue. As soon as I start amazon shopping or working on a spreadsheet it turns off. If I re-enable sleep, it dies a few minutes into sleep mode.

After all of this I now believe the issue has to be my RAM. But I am so frustrated at this point because I have spent a few months and a lot of money trying to fix this super irritating problem. I have been able to narrow down what causes the problem and predict when it will occur, but not pinpoint what the culprit is. Does anyone have any idea why this may be happening? I have read several forums and tried many recommendations to date without any luck.

 

[Brikic]

Could be the RAM like you said, take the Memtest and check if any suddenly shutdowns happen. If it happens, take out one ram stick and check if it happens again. Do that until you know which ram stick is causing the problem. If it isn't the RAM take the Perfomancetest 9.0 by Passmark.

 

[d_nussbaum]

Thank you for your response Brikic, unfortunately when I tried both the memtest and the performance test last night neither indicated any issue with memory. What is strange is that upon starting the computer the motherboard speaker beeps once indicating a DRAM refresh failure.