Phantom reset gremlin

[carnex]

So, I have messed up problem and can't diagnose it on my own without investments. So, i would be grateful if somebody could bestow some wisdom on me since I'm not about to cough up 100+ eur on power supply unless I know it's the problem.

 

So my configuration is

 

AMD ryzen R5 1400 Box Cooler

MSI B350 PC MATE

Coirsair Vengance DDR4 3000 2X8gb kit

ASUS Stryx RX470 4GB

LC POWER LC6550GP (only 4 pins for CPU power supply)

WD Green 240gb SSD

TOSHIBA 500 500gb HDD

CASE, MS BLACK WIDOW (surprisingly good silent case from cheapo Croats, patents be damned)

Windows 10 Pro

 

Now, problems and points. Computers resets out of the blue. Room is hot and CPU, even in idle, goes to 50+ even with side open but that doesn't seem to matter since it's stable at 95 while crunching with Prime95. Also, mentioned power supply ran AMD FX 8300 + RADEON RX380 at one point without breaking a sweat. Worst I got from it was to get CPU voltage drop down to 1,13 (out of 1,2 nominal) under prime 95 full cpu blast.

 

So few things that cause reset on command, usualy even before entering gameplay. Tropico 4, Tropico 5, XCOM (yes, first one) 3D mark (although one time it ran 4 times without issues)

Few things that work without a hitch. Prime 95, Witcher 3, Doom 2016, PassMark BurnIn, any productivity program although I did get occasional surprise reset there.

 

Also Windows logs don't log anything that would stand out. And no, I don't have access to good power supply unless I want to force two friends who do have them to dismantle their water cooling.