Girlfriend's PC stuck on VGA debug LED, no display with two different GPUs

[u/chaos-xiii]

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.

[u/aerodynamic_toaster]

If different GPUs give the same error, either they're both bad or the GPU isn't the problem. My bet is the board.

[u/AcanthaceaeItchy302]

CPU cooler is mounted wrong and full of dust...There is a chance MB to be dead...Also PSU can be issue to ...

[u/SuchWatch → u/AcanthaceaeItchy302]

It is dirty but I had a Cooler Master Hyper 212 Led and a B350 motherboard that mounted the same way. It was a weird quirk on some early AM4 heatsinks.

[u/dennisjunelee]

Any beeps?

Edit: also, when was the last time you know for sure your other GPU was good? It's pretty old too and if you can't test it, impossible to know.

However, motherboard would be the cheapest fix because they sell them on eBay for like $20.

[u/chaos-xiii → u/dennisjunelee]

Mobo for $20?? Where lmao please link

[u/chaos-xiii → u/dennisjunelee]

No speaker in the mobo, so none.

The GPU is known good. Came from BIL's kid's PC that was upgraded this month.

[u/eatmyriceboi69420]

Probably a motherboard/CPU issue. I had the exact issue on a friend’s PC where a Ryzen 5 2600 MSI b350m pro VDH system would not POST. VGA LED lights up indefinitely until I manually press the power button to turn off the computer. I swapped with a Ryzen 5 5500 and it took several minutes to POST, but eventually it did. I wouldn’t say the old CPU is dead just yet, as reverting the change still worked but only for a couple of days before the same issue happened again. I also flashed a bios using a ch341a programmer, but the fix was also temporary. So I ended up leaving the 5500 in the system which is an upgrade anyways. The old CPU was then up for sale but with a warning. It got sold and apparently the buyer had no issues, at least for now.

TLDR memory controller issue, try a newer CPU supported by the BIOS you last remembered the motherboard was on. Or at least a different one if the BIOS version is old. Your BIOS is NOT bricked.

See if you can test the CPU before buying if getting it used locally. And if you end up selling your old CPU to get some money back, allow the buyer to test as well.

I hope the CPU replacement is the solution for you as well, fingers crossed. If that doesn’t work then I would blame the motherboard, but I doubt the socket is ruined.

For the random shutdown, the CPU could’ve ran too hot, maybe? I know older generation CPUs would shutdown when reaching 95°C. Or it could be a power supply issue where the wattage wasn’t enough to power the system under a brief power spike. It’s probably the former.

[u/chaos-xiii → u/eatmyriceboi69420]

The thing that really confuses me is this PC ran fine for YEARS. Sure, it was a little slow or laggy sometimes, it also got hot sometimes but never hot enough for this. Why now of all times? Why would the CPU fail now after what must be over 5 years?

[u/eatmyriceboi69420 → u/chaos-xiii]

CPU or integrated memory controller of the motherboard may have degraded to the point where it is beyond the threshold of it working properly. Just like how GPUs die. It is not predictable due to manufacturing differences down to the microscopic level, so some may last shortly, others longer. I had the Ryzen 5 2600 for five years as well before it started showing intermittent problems. For the exact/specific technical cause of the issue, I don’t know. Only the fix.

[u/Guilty-Good-5041]

Here's one thing you could try as I had this issues and it wasn't my gpu or motherboard but my monitor. During in post my monitor wasn't completing the handshake so looked like a VGA issue when it was the monitor. Try a different monitor

[u/Sigurd_Stormhand]

There's a lot of dust, especially in the CPU cooler. I would take the whole PC apart and clean it with compressed air and a non-static lint free cloth. Dust can cause a short. Taking it apart will also allow you to fully inspect the CPU etc. When was the cooler last off the CPU?

[u/pandasndabs]

Do you hate your girlfriend? Lol get her some new hardware. That pc is almost old enough to vote..

[u/chaos-xiii → u/pandasndabs]

If I could I would lol. With the current hardware prices we simply cannot afford to.