PC loses monitor signal but still running and is unresponsive

techfreak9356 · November 24, 2019

Hi, recently, I have been experiencing issues with my build on randomly losing monitor display and then becoming unresponsive but still is running like nothing's wrong with it.

My build:
PSU: idk the brand, 700W switching (the cheap ones you can find at ebay)
MB: Gigabyte H110M-H
CPU: Intel Pentium G4400
RAM: HyperX Fury DDR4-2666 8GB (4GBx2)/Teamgroup Elite DDR4-2133 (4GBx1)

This computer has been given to me by my uncle before he went abroad, with the Teamgroup RAM stick installed about 6 months ago. Everything is running fine, then a month later, there was a sale for a HyperX DDR4-2666, which happened to be cheaper than the DDR4-2400 version of that stick for a limited time, since I'm planning to upgrade soon to a Ryzen 5 and B450, I bought two sticks. I installed them and everything is working fine, even though the speed is only at DDR4-2133. I have researched about the RAM stick being held up at a lower speed than usual, and I can't find much articles saying it's not good for my RAM. Everything is working flawlessly though. Then I replaced the stock Intel heatsink with a DeepCool IceEdge Mini v2. I even went on torture testing my PC (Prime 95) after installing the new RAM and heatsink, and everything was fine.

So, fast-forward 5 months later, we had a Typhoon in our country which had strong winds, and caused multiple abrupt power outages before totally blacking out. I am using my PC at that time encoding on Excel, when power first went out then came back about 10 seconds later. I was eager to turn my PC back on to check if my work was saved, and there was some saved, so I kept working as power seemed to be ok, but voltage regulator was clicking frequently, then power went out again. This happened about 4 times before power went on to normal. Then the computer lost signal on the monitor but is still running (although no longer responding to anything except hard reset). This was my problem which went on repeating itself at random times (even on the BIOS and POST screen it goes like that). CPU Temps are at the 28'C (idle) - 41'C (on load) range, so overheating isn't likely the problem. I'm confused now and still have no idea what is the likely culprit.

Btw my system cooling is made of the following:
3 x 80mm intake fans - 4-pin molex, full speed
1 x 80mm side exhaust fan - 4-pin molex, full speed

1 x 80mm stock intel cooler (DIY'ed to act as an exchaust) - 4-pin PWM, always set to full speed
1 x DeepCool IceEdge Mini FS 2.0 (heatsink w/ 2 heatpipes and 80mm fan) - 3-pin PWM, full speed

Here's what I did so far:
- The usual basic troubleshooting (hard reset, reseat connectors, clean and reseat RAM sticks)
- Changing thermal paste for CPU heatsink and Chipset heatsink (to rule out overheating)
- Glued a fan next to the chipset heatsink (to rule out chipset overheating)
- Installed the latest BIOS verison - v24 (to rule out BIOS probem)

- Tested the HyperX RAM on MemTest86 on stick 1 only, stick 2 only, and both sticks together (to rule out RAM issue)

- Clean installed Windows and installed drivers from manufacturer website (to rule out software and driver issue)
- Swapped back in the Teamgroup RAM and running Prime95 (again, to rule out RAM)
- Tested on Prime95 with CPU fan off, rear exhaust fan acting as CPU fan since gap between is just a few centimeters (to test if thermal paste is applied bad)

In spite of everything I did so far, the problem still persists. I checked event log everytime, but all I can find is that "the system shutdown at *time stamp* was unexpected" there were no indications of a driver problem, or a software problem in event viewer, so my likely suspect is a hardware issue. Can anyone help me out with this? I would like to hear some likely culprits before I start buying either a new PSU (Silverstone ~600w -ish), CPU (Ryzen 5 3400G), Motherboard (B450 Aorus Elite, or a similarly priced B450 board *i'm considering the TUF Gaming B450M*).