PC black screen rebooting even after PSU and Motherboard replacement

as the title reads, the PC has been giving me grief for the last past month, continually black screen rebooting, when under load and even sometimes just scrolling the web. first thinking it was the power supply. I replaced the power supply about three weeks ago and still nothing. next after about two weeks of troubleshooting software, and still not getting anywhere, even with under volts, i swapped the motherboard for one with better VRMs, thinking it was due to overheating of the motherboard(asus b360-f gaming to asus z390 -f) It was working just fine but once i’ve gone back into games, maybe and hour or so later it once again black screens. I have no idea what it could be. I am so defeated from this and just want to be able to use my computer again after work. My last guesses are that it could be a failing hdd or due to a RCA to HDMI adapter i have plugged in for my second monitor that is a crt but i have no clue and have already sunk $180 into just more grief. Any help would be greatly greatly appreciated. I tried to Run V2 but i get a red text reading this:

& : The term '.\resources\main.ps1' is not recognized as the name of a cmdlet, function, script file, or operable
program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:2
+ &'.\resources\main.ps1'
+ ~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : ObjectNotFound: (.\resources\main.ps1:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException

i ran DM log collector and have that on standby if that would be helpful. Thank you

-Andy

system specs:

i9 9900k

Asus ROG STRIX Z390-f

EVGA RTX 3060TI

g.skill trident z 2 3200 and 2 3000 mhz ram sticks clocked to 3000mhz

windows 10

Thermal take 750w gold psu

You say the last past month, I suppose this means that before it was working okay. Can you associate the problems with a change done, either hw or sw? It's also useful to know if the system was built new years ago, or with 2nd hand parts, adquired (not built by you) new or 2nd hand,...

It sounds as a hw problem, but it could also be a sw one. Open an elevated prompt and run these two commands that will check the OS and repair the errors they find, in case they do:

Dism /Online /Cleanup-Image /RestoreHealth
SFC /Scannow

The HDD isn't the kind of hw that uses to cause rebooting BSODs by itself (btw: are these the only kind of instability issues that you're having?), unless the cables are bad or badly attached. I have never seen it with HDDs, but if a mass storage device starts being unreliable with info recorded, it's time to replace it asap. Take into account that a brand new device won't fix the info errors accumulated before.

If it's a hw problem, it's more about time than about money. I suppose there're reasons why you replaced the PSU and the mobo, instead of say the memory and the graphics card. There must be a reason for every change or proof. Why did you try undervolting? Was it for high temperatures? But undervolting alone is calling for instability.

Memory is a common culprit of spread instability and you could try running with half the memory for instance. I don't think it's the HDMI adapter although it could be the fact that you're using two monitors (hence, try with one) for either a drivers/OS issue or a vcard hw issue.

I'm not expert myself in the event logs although others here could help. According to Intel the i9-9900K supports officially DDR4-2666, is it stable at that frequency? Is the system stable with everything at stock clocks? Hw malfunctioning (for overclocking or other causes) means things like (in binary) 1 AND 1 = 0 , 1 OR 0 = 0, you store 10010110 in memory and get 00010110,... and there aren't sw remedies for avoiding or working around such hw errors, only for trying to avoid some consequences.

I tried stock, and it still presented the same crash. I will try to downclock the memory to 2666 again and see if it works like that but it did not work at 2666 on the b360 board

Uninstall any / all non-Microsoft antivirus and / or firewall using the applicable uninstall tool:

[KB146] Uninstallers (removal tools) for common Windows antivirus software

Make sure that extract all is clicked before launching the log collector.

would disabling the antivirus be enough?

You can try disabling third party AV and firewall software.

Sometimes third party AV and firewall software drivers misbehave and are the cause of BSODs.

Bitdefender is one of the top interfering AV software.

It's best to uninstall third party AV and firewall software and use Microsoft defender.

After troubleshooting has completed you can install third party AV and firewall software or continue using Microsoft defender.

The V2 link was not able to be opened.

compressed zipped folders error.