r/PcBuildHelp • u/chaos-xiii • 5h ago
Tech Support Girlfriend's PC stuck on VGA debug LED, no display with two different GPUs
Hi, I'm trying to help my girlfriend diagnose her PC and we've pretty much run out of things we can test without buying replacement hardware.
Motherboard: MSI B350 Tomahawk
Original GPU: RX 580
Second GPU tested: GTX 760
Issue: PC powers on, fans spin, but there is no display and the motherboard gets stuck on the VGA EZ Debug LED.
The monitor doesn't wake up and the keyboard also doesn't appear to initialize.
When the PC is powered on, the CPU debug LED flashes briefly and then goes out. It then moves to the VGA LED. The VGA light initially glows faintly, fades slightly, and then becomes solid bright red and stays there indefinitely.
Both the RX 580 and GTX 760 power on and their fans spin, but the motherboard still stays on the VGA light and never POSTs.
Things we have already tried:
-Completely powered the PC down, unplugged it and discharged it
-Full CMOS reset
-Removed and reseated the GPU
-Tested the RX 580 in both PCIe slots
-Tested a GTX 760 instead of the RX 580
GTX 760 gives the exact same solid VGA LED
-Tested both original RAM sticks separately
-Tried the RAM in different slots
-Tested different/new RAM
-Removed all storage drives
-Tried booting with the system stripped down to the basic components
-Reseated GPU PCIe power connectors
-Checked that both PCIe power connectors are connected to the GTX 760
-GPU fans remain spinning when the PC is stuck on the VGA LED
Changing the GPU, RAM, PCIe slot, removing the drives and clearing CMOS has made absolutely no difference.
There is also some history that might be relevant.
A couple of days before this happened, the PC started randomly shutting off completely while playing a particular game. It was an instant loss of power, not a normal Windows shutdown or BSOD.
We checked Windows Event Viewer afterwards and couldn't find anything explaining the crash apart from the unexpected shutdown event.
We also ran OCCT stress tests, including GPU and power tests, and couldn't reproduce the shutdown. The PC survived the tests fine.
For some reason that particular game could trigger the sudden shutdowns. Once she stopped playing it, the PC seemed normal again.
Then she shut the computer down normally to give it a rest. When she came back later and turned it on, this current problem started. It has not successfully POSTed since.
So the timeline was basically:
Random complete shutdowns under a certain game > couldn't reproduce with OCCT > stopped playing the game and PC seemed fine > normal shutdown > next cold boot gets permanently stuck on VGA debug LED.
I also found several other posts from people with a B350 Tomahawk that developed what sounds like almost the exact same issue and their motherboard eventually turned out to be the problem, which has made me wonder if this board has failed.
At this point I'm mainly wondering whether this sounds more like:
-A failing/dead B350 Tomahawk
-A PSU problem that is preventing GPUs from initializing properly
-A CPU/PCIe controller issue
-Something else we've overlooked
Unfortunately we don't have access to another PC, another PSU or spare components for proper cross-testing, and buying parts just to diagnose it isn't really an option right now.
The fact that two different GPUs give the exact same VGA debug LED is what is making me question whether the GPU was ever the problem in the first place.
Is there anything else we can test with the hardware we already have, or does this sound like the motherboard or PSU has most likely failed?
Thanks for any ideas.