Question PC losing monitor signal randomly

[ElJuanito]

hi there,

I have a very weird issue with my PC.

Background: I built the machine myself from components earlier this year. I'm not a tech professional but this isn't the first PC I built and I can't imagine what mistake I could have made that produces the issues described below. The components are the following (all new out of the box):

• Mainboard: Gigabyte Z790 AORUS PRO X
• CPU: Core i7-13700KF
• RAM: Corsair Vengeance DDR5 (2x16 GB in slots 1 and 3)
• GPU: ASUS GeForce RTX 4080 16GB GDDR6X Noctua OC Edition
• SSD: SanDisk Ultra 3D 4 TB (+ 2x Western Digital from my old machine, can't remember the model)
• PSU: be qiet! Pure Power 12 M 1000W
• Monitor: Dell U2723QE (connected over HDMI, using 4k)
• OS: Win11 Home (Windows and Graphics drivers are up to date, didn't touch the BIOS so far)

So, the issue is that the machine will randomly loose the monitor signal, i.e., the screen goes dark and I get a message like "no HDMI input detected". The really weird part about that is, that this behaviour is progressing, meaning it happened every couple of days in the first weeks, then actually nearly vanished and now in the last week or so, it's suddenly been happening almost all the time. At first I thought it was a power issue with the GPU or a thermal issue because in the beginning it was only happening while running (demanding) games (Starfield, MSFS 2020, RDR2). However, now it also happens in games like Civilization 6 or even sometimes just in Windows when there's basically nothing going on. When it happens during a game, I can still hear the game sound, so I know it's not the system itself that crashed, it's only the video output. Changing cables didn't help either.

I did not see any error codes or anything that one might expect if that were the case (however, I don't really have a chance of seeing such error messages since I don't have onboard graphics and if the GPU goes down, it's a black screen...not the best decision in hindsight but I got a really good deal on the CPU). Reliability Monitor in Windows also has no indications. Also, I can see the fans spinning etc. and the machine is pretty quiet even under load. Diagnostic software such as HWInfo also doesn't show me any high temperatures. I ran Furmark for 2 minutes just to see what happens and the GPU got to 75°C which I guess is within reasonable limits in that situation (?). At idle it's around 30-40°C as per Nvidia GPU Tweak III. I have the tower right next to me on my desk (side panel open) and I can barely even hear it is running.

Another discovery: Yesterday and today I noticed that it happened when I moved the tower a few centimeters which lead me to think it might be a faulty cable somewhere or something like that (even though, when it happened before, the machine was standing perfectly still). I just had a closer look inside but I can't see any dodgy cables and for the monitor signal to vanish, I guess it would have to be the PCI connection or the power connection for the GPU - both of which aren't exactly connections that would disconnect from a tiny little movement/shake. Anyway, I just had another look at them and they seem perfectly fine. The GPU sits as tight as a card of that size/mass can sit in a PCI slot, it also came with a little standoff to prevent it from bending, which seems to work well - the card is perfectly level as far as I can tell.

One other thing: I am using the same monitor with my MacBook over USB-C and I haven't had single issue with that for the 4-5 years I'm using that monitor. I guess I could try using a HDMI to USB-C cable from the PC but then I would have to change the cables in the back of the monitor every time I'm switching between computers and that would be really really annoying...so I'm trying to exclude all other possibilities first - also the HDMI input of that monitor worked fine over HDMI with my old PC for years, so I'm quite sure the HDMI jack isn't the problem. Sadly, I don't have another monitor around for testing.

At this point I'm running out of ideas on how to diagnose/fix this issue, so any ideas/tips/help is highly appreciated!

 

[rajdeep8]

When there is no signal on the monitor, is your gpu fans spinning as usual or spinning at a fixed speed?

 

[ElJuanito]

When there is no signal on the monitor, is your gpu fans spinning as usual or spinning at a fixed speed?

Funny thing, I was just about to add that to my post. Until today, the tower was under my desk, so I couldn't really tell if the fans went faster or slower when that happened (I just could see they are spinning at some rate). A few days ago, I set the fans on the GPU manually to 80% because I thought that might help, even though temperature doesn't seem to be an issue. But I reasoned it can't hurt to have them at 80% always since they're very quiet anyway. Also I set the GPU power target to 90% (rather than the default 100%) to exclude power issues, even though I can't see this being the issue either, given that it draws around 320W under full load and I have a 1000W PSU. Btw, I also made some changes with nvidia profile inspector to optimize performance in MSFS2020, but that was quite a while ago and the issue was already present before I did that.

Anyway, now I put the tower next to me on the desk and opened the side panel to get a better look. Just 5mins ago I did another Furmark run to see if I can "get it to crash" and maybe see something going wrong inside. It did actually loose the monitor signal after about 5mins (at a temperature of only 69°C) and when it happened I could hear something spinning up pretty good for a few seconds - I think it was the fan from the CPU cooler though. I don't understand why this would happen but I'll keep the tower next to me and check if that happens every time the monitor goes dark...

edit: new idea...could this maybe be an GPU undervolt issue? The voltage in GPU Tweak was set to 75% (I think that was the default setting, but I'm not absolutely sure)...I set it to 90% to see if that changed something and now I was able to play Starfield for about 5mins without the signal loss issue occuring (in the last few days, the signal would drop usually after a minute or even less). However, that wouldn't really explain why it happened so randomly and even in Windows (?)...

 

[rajdeep8]

Even I am facing the same issue.

One day my pc was not giving display output same as your display port no signal.


At first, I thought its GPU issue and unluckily my gpu is out of warranty.

So I went to a local repair shop.

They said one of its ic was damaged because of monitor back current by dp cable.

They repaired and advised to use hdmi instead of dp.

And within 36 hours I faced the same, suddenly no display after a reboot. I thought it was the gpu again.


I went to the repair shop again but surprisingly it was not the GPU fault actually. It was working.

They said there could be carbon layer in my pcie slot.


I came back home and inserted the gpu inside pcie slot and it started to work.

Then after 2 days same, suddenly no display. after few reboots


This time I went to the repair shop with almost everything, mobo cpu ram gpu, I just left my psu behind in my home. (PSU was tested with a multimeter and voltages were fine, its cv650 corsair, 3y old I highly doubt if it's psu fault)


And it worked in their repair shop and I'm frustrated.


Back to home, worked for 1 hour then same.


After 1 day I cleaned the pcie slot and gpu pins with a toothbrush and luckily, its been more 3 days working.


CPU fine
Gpu fine
Ram fine
Psu fine
Psu fine
Hdmi cable is fine


The only thing I can assume broken/causing the problem is my motherboard (b450m steel legend) as rest of the components are OK. And no display occurs for me after few reboots or starting the PC the first time in a day. Never went to no display while working /playing games/running stress test for 4-5 hours.

But don't know what's the issue 🥺😅

 

[rajdeep8]

if I'm not wrong your mobo has a debug light feature, any indication?

Try using 1 ram stick at a time

Swap if needed as you have two sticks

 

[ElJuanito]

Even I am facing the same issue.

One day my pc was not giving display output same as your display port no signal.


At first, I thought its GPU issue and unluckily my gpu is out of warranty.

So I went to a local repair shop.

They said one of its ic was damaged because of monitor back current by dp cable.

They repaired and advised to use hdmi instead of dp.

And within 36 hours I faced the same, suddenly no display after a reboot. I thought it was the gpu again.


I went to the repair shop again but surprisingly it was not the GPU fault actually. It was working.

They said there could be carbon layer in my pcie slot.


I came back home and inserted the gpu inside pcie slot and it started to work.

Then after 2 days same, suddenly no display. after few reboots


This time I went to the repair shop with almost everything, mobo cpu ram gpu, I just left my psu behind in my home. (PSU was tested with a multimeter and voltages were fine, its cv650 corsair, 3y old I highly doubt if it's psu fault)


And it worked in their repair shop and I'm frustrated.


Back to home, worked for 1 hour then same.


After 1 day I cleaned the pcie slot and gpu pins with a toothbrush and luckily, its been more 3 days working.


CPU fine
Gpu fine
Ram fine
Psu fine
Psu fine
Hdmi cable is fine


The only thing I can assume broken/causing the problem is my motherboard (b450m steel legend) as rest of the components are OK. And no display occurs for me after few reboots or starting the PC the first time in a day. Never went to no display while working /playing games/running stress test for 4-5 hours.

But don't know what's the issue 🥺😅

maybe get a very cheap GPU just for testing? A real cheap one probably will cost you less than another 1 or 2 trips to the repair shop. If it doesn't occur with a different GPU, then you at least know which part is to blame...I'm thinking about doing that myself actually, I have an older GPU gathering dust - so far I just didn't want to go through the hassle to exchange them....but if the issue doesn't resolve itself that's probably my next move...

 

[ElJuanito]

just made an interesting discovery: While I do not have a 2nd monitor for testing, I do have a smart TV, so I simply went ahead and mirrored the screen over WiFi to that smart TV.

Result: When the PC monitor went black, the image on the TV simply froze...no error messages, no nothing, it just froze in-game.

So I guess that means the culprit is not the PC monitor (although I still don't understand why it's just going dark) but the system itself does actually "crash" (or rather "freeze"). To me that points to either the GPU or the motherboard/CPU, although anything I can check via software seems normal and these are basically brand new parts...I do have warranty on all of these but if I can't find out which part actually is the problem here, I don't even know what to replace :/

 

[rajdeep8]

Try your monitor with a laptop probably. If it works fine then it's not your monitor.

I tested my monitor using my HP laptop and a hdmi cable.


Make sure all of your display drivers and adapter softwares are uptodate.

just made an interesting discovery: While I do not have a 2nd monitor for testing, I do have a smart TV, so I simply went ahead and mirrored the screen over WiFi to that smart TV.

Result: When the PC monitor went black, the image on the TV simply froze...no error messages, no nothing, it just froze in-game.

So I guess that means the culprit is not the PC monitor (although I still don't understand why it's just going dark) but the system itself does actually "crash" (or rather "freeze"). To me that points to either the GPU or the motherboard/CPU, although anything I can check via software seems normal and these are basically brand new parts...I do have warranty on all of these but if I can't find out which part actually is the problem here, I don't even know what to replace :/

 

[ElJuanito]

status update for those interested or having similar issues:

After having a look at the internal cabling etc (nothing to fix as far as I could see), I put the tower under my desk again. It has been running basically all yesterday without a single issue. For now, I guess I'll just leave it as is and hope there simply is a dodgy electrical contact somewhere that has now been set right by the movement and will stay as it is. Weird, but as long as it works...

 

[rajdeep8]

Same with me, started working from lat 3 to 4 days without any issue.

 

[Randi Poling]

Could honestly be the HDMI cable shorting it out or something. HDMI cables can be weird sometimes. Potentially moving it to where you did has made whatever is going on in that cable, not cause a short.