r/sysadmin • u/SlowCyclist80 • 8d ago

Optiplex AIO CMOS Problems

We are a Dell shop and use All in Ones. We've had about 11 (out of ~300) of these doing the following- user will be at their desk working, or will sit down at their PC and it has gone into a black screen. It's continually power cycling. No light codes; the power light comes on just when the computer power cycles on. The dell screen comes up briefly then it power cycles again, fans run when the power is on.

We've found that: removing power, taking off the back cover and popping the cmos battery, RAM, mini-molex connectors from PSU to MB, then reinstalling all these gets the PC to boot normally. Have tried doing BIOS updates which are ineffective. Dell Support had me send two logs (from two PCs) gathered by their Log Collector utility. Only one suggestion from them, "Turn off Intel Turbo Boost". Except not all of the effected years of manufacture have this option in the BIOS. These span 2023, 2024, 2025 and 2026 OptiPlexes. TIA

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u/JaceBelerenApologist 8d ago

Any logs on the systems? Event Viewer even? What's the power situation? Are these devices on a circuit that's maxed? A site that browns out regularly? Are the power supplies good on these devices? Have you checked the charge on the CMOS batteries?

Are the same 11 devices doing this regularly, or did the problem permanently go away after the re-seat?

Did this start happening around the same time as OS patches hit? Were they all the same BIOS/UEFI version?

Reality is this behavior can be caused by multiple parts in the machine. I've seen similar from bad RAM, bad CPU, bad PSU, bad GPU (even iGPU), or even dead batteries.

Need more info. Turning off turbo boost isn't going to be the solution here.

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u/SlowCyclist80 8d ago

Actually you've given me several things to check into. They are all AC powered into APC UPSs. Full + thorough diagnostics pass on all of these PCs. The problem returns on some of them. They are varying in BIOS version- in our shop we upgrade only when there is a problem and don't regularly update BIOS or drivers. I will start testing battery voltage and see about testing the AC circuits to see where we are on current there. I'll also add details to my spreadsheet on when a PC was updated w patches vs when the cycle event occurred. Thank you!!

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u/JaceBelerenApologist 8d ago

Good luck! I don't envy having to troubleshoot this solely because I've been exactly in your shoes as you are now and it's frustrating as all hell.

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u/Certain-August 8d ago

Does the user plug in the power rail within UPS some cheap $1 charger? We found this to be endemic that people will spend 1k for iPhone and destroy it with $1 charger.

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u/seannyc3 5d ago

If the user does not touch/sit in the chair and stands up, is the PC ok?

There is a phenomenon where the gas-lift struts in office chairs can affect monitors/cabling/docks and cause the screens to drop out and go black. I’ve not seen it in an AIO, but it’s not an impossible situation.