Hardware guys - What the H E double L is this sound??

Today I was going to install Windows on a used Optiplex 3070 i5-9500 that has a m2. nvme. When I powered it up and accessed the bios it started making a very loud grinding/buzzing sound. I reset the bios to default but it kept happening. I accessed the boot menu. Same thing. When I disconnect the graphics cable it goes away no matter if I use DP or HDMI connection. I tried multiple cables, but it didn't make a difference. This sound is coming through the speakers in my monitor, not from any internal PC speaker or from inside the case itself. I can disconnect the graphics cable and the sound goes away.

It's not the monitor because a second Optiplex worked fine. It did let me boot into my Windows install usb. I installed Windows and all the drivers, including graphics. IThe sound remained throughout the entire install. Windows installed normally and works normally.but still have this loud sound. I suspect its the CPU since it has onboard graphics and the sound is passed through the graphics cable or some kind of interference through the mobo. What do you guys think?

Here's a short video so you can hear it. I've never heard anything like it and I'm stumped.

Hi @glasskuter , access is denied in your link.

@Fabler2 Try this

glasskuter said:

@Fabler2 Try this

IMG_0128.MOV

drive.google.com

Click to expand...

Had to download the file to listen to it. Sounds like some electrical interference? Try with (external) mic off is the only suggestion I can think of.

@glasskuter



It sounds like maybe the Optiplex has an internal grounding or shielding issue... somewhere.
Unfortunately, those kinds of problems are hard to track down.

I would probably try something like this...

Get a wire, 12 or 14 gauge, strip the ends, and hook one end to the screw that holds the outlet cover plate on.
Any copper plumbing pipe you can get to would work also.
Then with the case open, touch the other end of the wire to various locations in the running Optiplex that should be grounded.

Places like the motherboard screws, any metal covers over things like sound chips, the grounded areas on the rear of the case, etc.

If any of those cause the noise to stop... then you've found your grounding issue.

Make sure not to touch anything in the Optiplex that has voltage on it.

Ofc the best option would be to just return the Optiplex and get a different one.
Like... a bent pin on the CPU won't show up in the test I outlined above, but could very well cause the problem.

Yes, it sounds like an electrical issue. May be a failing capacitor. Any smell?

Can you swap the PSU's?

@glasskuter

I agree that if you only hear the noise when the cable from comp to monitor is plugged in, that it's probably gonna be the CPU or the grounding of the cable itself.

Also, as @kelper mentioned, it could be a bad capacitor or VRM, located in the circuits to and from the CPU.
If one of those went bad, and lost it's ground or blocked a ground to one of the CPU pins... you might see the same problem.

See if any of the caps, near the CPU are swollen or leaking.


For example...





And on a more modern motherboard... NOT leaking or swollen.

@kelper No smell I can detect. This is a SFF PC with a Dell proprietary PSU so I don't have another one except the one in my own Optiplex which I ain't gonna tear apart. Though the connectors would probably be the same, I don't think it would fit anyway as mine is a MT form factor.
Everything about these Dells is proprietary and nothing is simple when it comes to hardware..

glasskuter said:

When I disconnect the graphics cable it goes away no matter if I use DP or HDMI connection.

Click to expand...

Try a set of headphones, if possible..., see if you get the same noise.

As others mentioned above - that sounds like electrical noise/interference - leaking into HDMI/DP audio.

Are the PC and monitor - plugged into different power outlets? If that doesn't help, possible/common culprits:

- grounding/shielding issues on the motherboard
- failing PSU causing power ripple or/and coil noise

Also reminds me of fan bearing failing (more like a coincidental resemblance - in terms of screeching noise), which is easy to check - by unplugging the fan.

Tho, CPU/iGPU failing doesn't sound like that - and you'd notice other issues (artifacts in particular if the iGPU or random restarts if the CPU - even failing to start eventually).

Is it possible to connect video and audio to the monitor separately? Or can you connect speakers?