The PC stops working unexpectedly, even after replacing nearly all components.
The PC stops working unexpectedly, even after replacing nearly all components.
The list includes RM750x. Was this the initial power supply unit or a replacement? The other unit is a different model. Also, were all PSUs purchased new or did some come from used/refurbished sources?
Random reboots or shutdowns usually stem from two problems:
1. CPU/GPU overheats and to avoid damage, the system powers off.
2. PSU cannot provide sufficient power to the GPU or fails to maintain stable voltage for the PC's operation.
First, check your CPU/GPU temperatures, both when idle and under load. If temperatures are normal, it’s likely the PSU is the issue.
Now, RMx is a reliable PSU and unless your RM750x has a fault, I wouldn’t suspect a power supply problem.
What are your temperatures?
Also, power-off can be triggered by MoBo VRMs. Another possibility is the main electricity grid. A UPS helps manage these issues.
The situation is quite limited when it comes to getting the PC running. Elevated CPU or GPU temperatures can cause shutdowns due to thermal throttling. However, since your temperatures are manageable, the issue likely isn’t related to heat. The power supply unit (PSU) also warrants consideration. Given you have a reliable PSU, it’s difficult to attribute the fault to it, particularly because you’ve tested with a second unit—though using refurbished units isn’t advisable. It’s unlikely both high-quality PSUs would share the same problem. Also, a PSU becomes more likely suspect when the PC shuts down under heavier loads, such as during gaming. Since your system powers off even when idle, assigning blame to the PSU is challenging.
The next point should be the main power source. Regarding this, did you notice any power interruptions immediately after installing the new PC? Or did problems emerge later?
For power grid concerns, the solution would be an UPS system. For instance, a line-interactive unit with a true sine wave output and around 1300VA/750W capacity would be ideal. Power outages can be so brief that you might not even notice them—like the RM750x 2021 version which has a hold-up time of 26.6ms. This means a short interruption (up to 26.6ms) allows the PSU and PC to continue operating. However, if the outage lasts longer, such as 50ms, the PSU will shut down, cutting power to the system entirely.
To illustrate just how brief 26.6ms is, one second equals 1000ms. The average human reaction time is about 250ms; with practice, it can drop to 190-200ms. So, a blackout lasting only 50ms would be imperceptible. Yet the PSU can detect it. This is why an UPS is necessary.
Because of these subtle interruptions, both PCs are protected by an UPS (one per unit). If you’re curious about UPS options, I can provide more details in my next message. However, keep in mind that high-quality UPS units come at a significant cost.
Additionally, there’s the possibility of MoBo VRMs (Voltage Regulation Modules). While they rarely fail, they could be a factor. If they do occur, the only solution is replacing them with a new unit.
It’s hard to pinpoint the exact cause.
All signs suggest either excessive heat or a faulty PSU. But since your PC shuts down even when idle, the main electricity grid issue becomes more plausible (or occasionally MoBo VRMs). Personally, I’d test a third, reputable PSU—preferably from a trusted brand like Seasonic or Super Flower—and avoid using refurbished units. A third attempt might reveal the problem.
3rd time may be the answer: if the issue persists even with a different, reliable PSU (such as Seasonic Focus or Super Flower Leadex), then investing in a UPS would be wise.
If you’d like, I can share more details about UPS options in my next reply. Just remember, premium UPS systems are quite expensive.
Thank you for your feedback. I believe the issue might be related to the power supply system, as I had experienced frequent shutdowns even after setting up the PC. The recent rise in shutdown frequency over the past month makes it less likely that a UPS would be the cause. Could you provide more details about UPS systems?
In case there are any problems, it increases the chances that UPS will be affected even more. Grid instability, which is becoming more common, suggests a greater demand on the electrical network (whether in your local area or across the country). With increased load on the grid—especially because electricity supply is limited—more problems such as surges, brownouts, and blackouts would likely occur.
In my view, every computer should include a UPS.
UPS devices can generate three distinct waveforms:
1. Square wave – the most affordable option, suitable only for very robust equipment like generators or motors.
2. Simulated sine wave (also known as stepped sine) – offers a reasonable price point and works well for most household appliances (e.g., refrigerators, washing machines, lighting).
3. True/pure sine wave – more expensive but delivers the cleanest signal, ideal for sensitive electronics such as medical devices, TVs, and PC power supplies.
Therefore, opting for a true/pure sine wave UPS is recommended. Simulated sine wave models may still function, though with limitations; details are available below.
When selecting a UPS, pay attention to:
- The output waveform (square, simulated sine, or pure sine)
- The design type (stand-by, line-interactive, online)
For more information on differences between waveforms and designs, you can refer to:
https://suvastika.com/why-choose-a-sinew...erter-ups/
And for detailed explanations about UPS types, see:
https://www.eetimes.com/document.asp?doc_id=1272971
Waveform and design details
For PCs, a line-interactive UPS is generally sufficient because power supplies can manage the brief transfer times of 2ms to 5ms. Regarding waveforms, true/pure sine wave UPS is optimal. Simulated sine wave models are cheaper but may not work reliably with Active PFC PSUs. You might encounter problems if you use a simulated sine wave UPS with an Active PFC power supply. Here’s what happens, how it occurs, and why:
Understanding which PSUs have Active PFC and which don’t is straightforward:
Every PSU with 80+ certification (such as 80+ Bronze or 80+ Gold) includes Active PFC.
What is Active PFC?
For further reading:
https://en.wikipedia.org/wiki/Power_fact...near_loads
Potential issues with simulated sine wave UPS using Active PFC PSUs
Switching to battery power can trigger several outcomes:
1. The UPS shows an error and forces the PC to shut down instantly.
2. The PC shuts down immediately.
3. The PC powers off from the UPS, but the PC remains on.
Why this occurs?
Simulated sine wave UPSes generate a zero output during phase transitions, creating a power gap. This interruption can affect Active PFC PSUs when they switch from AC to simulated sine wave output (battery mode).
What should you do next?
As mentioned, your PC can operate on a simulated sine wave UPS, but be ready for possible complications. If problems arise, consider replacing the simulated sine wave UPS with a true/pure sine wave model. Alternatively, go straight with a true/pure sine wave UPS.
Power requirements
When choosing a UPS, consider your PC and monitor power consumption. Don’t forget speakers or Wi-Fi routers if you plan to connect them as well. Printers, scanners, and similar devices usually don’t require UPS input because their startup power draw is excessive for the device to handle safely.
Setting a PSU’s maximum wattage as a baseline helps ensure your UPS has sufficient capacity, extending runtime and preventing damage. For example, with a 750W PSU, adding one monitor (typically 23W–52W) and a Wi-Fi router (around 12V at 3A = 36W) gives a solid foundation. Actual needs vary based on your hardware.
Choosing a reliable UPS brand is important. Good options include CyberPower, TrippLite, and APC. These are among the top choices available.
Note: The higher the power rating of your UPS, the longer it can keep your PC running before the battery depletes.
To provide a suitable recommendation, I need to know your monitor model or part number, plus any other devices you plan to connect. Additionally, your location (e.g., USA, Germany, Italy, Australia) is important so I can suggest models compatible with local power sockets.
The details you shared are really helpful.
My monitor is a Gigabyte M27Q and I'm located in the West USA. I don't intend to connect any additional devices to the UPS besides the PC and monitor.
That's 58W monitor,
specs:
https://www.gigabyte.com/Monitor/M27Q-rev-10/sp#sp
With 750W PSU and 58W monitor, total would be 808W.
UPS wise, good option is:
CyberPower CP1350PFCLCD (1350VA/880W, line-interactive, true/pure sine wave) UPS;
specs:
https://www.cyberpowersystems.com/produc...nformation
amazon:
https://www.amazon.com/CyberPower-CP1500...B00429N19M
It has NEMA 5-15R sockets that are common in USA.
Runtime wise, 800W load lasts for 2 mins.
But realistically, your PC's max load would be ~500W (~550W with monitor) and that gives you 6 mins of runtime.
And when your PC is idle (e.g web browsing), it should consume ~200W, making UPS runtime during blackout 27 mins.
UPS'es idea is to close and save your progress and then safely shut down your PC, when blackout appears. Rather than you loosing on an instant whatever you were working with.
This was actually the main reason why i bought UPSes for our builds as well. While blackouts are rare where we live, last blackout, before having UPS, costed me 2h worth of work and that was it for me.
Did my research and bought two CyberPower CP1300EPFCLCD (1300VA/780W, true/pure sine wave, line-interactive) UPSes,
specs:
https://www.cyberpower.com/hk/en/product...300EPFCLCD
The UPS i suggested for you, is actually the successor model of what i have.
My UPSes are 7 years old as of now.
Still going strong and catching even the shortest blackouts that i didn't realize were happening.