Question Computer no longer outputs to monitor

[AG-67]

Hello, about 2 years ago I built my desktop and it's been working fine. However, when I turned it on tonight my monitor remained in power saver mode with no output. Looking at the motherboard (Gigabyte Gaming 3) the VGA light was on and, on closer inspection the fans of the GPU would stop a few seconds after pressing the power button. The lights of the GPUs are both on however. I've tried some trouble shooting and am a bit stumped. No changes were made to hardware, software, or drivers between now and last night when I used it last. Here's what I've tried so far for testing:

• Basic checks: Ensuring that GPU, ram, power cables are properly seated (at both ends for cables).
• Tested both GTX 1080 TI (original card) and GTX 1070 with same result (VGA light on, no output to monitor detected).
• Tried second PCIe slot with both cards: same result.
• Tried second PCIe power cable from PSU for both cards (using same cable for both power inputs for GTX 1080 TI). Same result.
• Unplugged both DIMMs and tried a single stick for both sticks. Same result.
• Reset CMOS using both battery and jumper. Same result.
• Tested display port cable and monitor by connecting to laptop. Monitor detected and output successful.

I would greatly appreciate any suggestions as I've tried most of what I could think of. The issue doesn't seem to be with the GPU(s), PCIe slots, ram, or CPU (untested, but unlikely given that the system was working yesterday). That seems to leave the PSU or motherboard, but since I don't have backups for either I don't know how I'd go about confirming that (or how ot resolve the issue if I did).
My Build:

• Motherboard: Gigabyte GA-AB350-Gaming 3
• CPU: Ryzen 7 1700
• RAM: CORSAIR Vengeance LPX 16GB (2 x 8GB)
• GPU: MSI GTX 1080 TI Gaming X / EVGA GTX 1070 SC
• Storage: WD Black 256GB Performance SSD (System files) / WD Blue 1 TB SATA (general storage)

 

[SchuetzenHaus]

If it helps, I also had a couple display issues with my MSI GTX 980, where the drivers from the actual nvididia site didn't work or broke stuff, I had to download them directly from the MSI site. Maybe plug your monitor in to your Motherboard and try and download those?

 

[AG-67]

Unfortunately there are no onboard graphics, so I'm stuck using a GPU (and neither of the two I have on hand seem to be sensed). I'm leaning towards it being a problem with either the PSU or motherboard. I don't think it's a driver issue as I haven't updated the drivers recently.

 

[SchuetzenHaus]

I'll assume your motherboard doesn't have an LED debug panel? Are there any signs of errors anywhere with lights?

My main thought would be if it's even going through POST. If you take all the RAM out, does it give you the error beeps?

When you turn the computer on, do the fans go up to proper speed or does it say at a low RPM?

 

[AG-67]

It does have the LEDs. Originally the VGA LED was turned on and the computer did nothing else.

I just tried taking out both sticks of RAM and instead of the normal behavior the DIMM LED first turned on, then turned off and the CPU LED turned on. The computer then powered off on its own and started back up several times until I turned off the PSU.

The fans run as normal (when there is RAM), with the exception that the GPU fans go idle after a few seconds.

 

[Coputerhater]

I am having the same problem with my PC. I shut it down the other night tried to start it up next morning and got black screened on both monitors.
Mobo-Gigabyte Ga-78lmt-s2
CPU- AMD FX4300
GPU-GT730
RAM-8gig of ADATA
PSU-Venus 500w
Tried everything

 

[AG-67]

Update: I had some minor success last night when my computer booted, but it promptly stopped working again and I'm not sure why there was any change.

Immediately prior to booting I had swapped out the CMOS battery (Unplugged computer, removed battery, waited a few minutes and put in fresh battery). The computer promptly started up with full display. I then shut it back down and inserted the second stick of RAM, and it again turned on fine.

Finally, I swapped the graphics cards (1070 to 1080TI) and it stopped working again, exact same issue as before. Trying to swap the battery again did nothing, changing PSU cables nada, ditto for simply trying to unplug the PSU and hold the power, and (of course) swapping the GPUs back again also kept the same error, even after trying to swap batteries again.

So this is quite mysterious to me. It worked temporarily, but then stopped just as quickly and I really have no idea why. DOes anyone have any ideas here?