Input Voltage Randomly Dropping to 115V

Hi, my RM1000i's input voltage is being reported as randomly dropping to 115V from 230V (I am in the UK, 115V is the voltage used in the US). It never used to do this, the PC still works fine and all other voltages are fine so what's going on and why is it happening?

I've tried using a different surge protector with the same result. I've tested my sockets with a little socket tester and it says they're okay (although it doesn't measure the voltage). I have confirmed this behaviour in HWInfo and Aida64 as well as an old version of HWInfo. Could this still be a software issue related to a Windows update for instance, an electrical problem in the house or is it hardware? I have tried plugging the link cable into a different internal USB port and will report back.

My system is:

AMD Ryzen R9 3900X

Gigabyte X570 Master

32GB Crucial Ballistix 3600MHz RAM

Corsair MP510 960GB SSD

Phanteks P600S

Corsair RM1000i 1000W PSU

Palit GTX 1080 Game rock Premium

Noctua NH-D15S cooler

I plugged the cable into another internal USB header, Windows detected it on boot and installed the relevant drivers and so far it doesn't seem to be dropping the input voltage anymore but I'll have to do more testing to be sure as the problem is intermittent and I can't see how changing USB port would fix it.

Edit: it just happened again so this did nothing to fix it.

The PSU stopped dropping to 115V for the past few weeks, but yesterday I tried to turn the PC on and nothing happened except for the motherboard light coming on. The PSU has died after 4.5 years of service:

Some little bits of metal wire came out of the PSU grill when I removed PSU from the case and I think this green object did as well, so I think something might have exploded:

Problem solved, it was a faulty PSU. I will be requesting an RMA.

If that's what fell out of your PSU, it's not faulty. Not saying you still can't get it replaced under warranty, but as an FYI.... That's part of a metal-oxide varistor used for surge suppression inside the PSU.

 

https://electronics.howstuffworks.com/gadgets/home/surge-protector1.htm

 

Thing is, the MOV isn't supposed to blow like a fuse unless there's more than 30 seconds worth of surges with an hour.

 

What are your surge strips rated at?

Hi, it's this one: https://www.apc.com/shop/uk/en/products/APC-Home-Office-SurgeArrest-6-outlets-with-Phone-Protection-230V-UK/P-PH6T3-UK

It has a surge energy rating of 2030 Joules. I'm surprised that such a surge would damage the PSU yet leave my other components intact, (I didn't notice anything unusual although I know you wouldn't necessarily notice it). I have a Dell monitor, Corsair SP2500 speakers and a network switch hooked up to the same surge protector and they were fine.

Could the fact that the input voltage was intermittently reported as 115V have anything to do with this? I also noticed that the PSU would sometimes make a popping noise if I turned it on via the switch on the back, could this have caused the varistor to blow?

How often do you do this?

 

PCs are meant to be in standby when off. You should only be flipping that switch on the back if you're going to do work inside the PC.

 

You know how the PSU has a big capacitor? That's remains charged with 400V+ as long as the PSU is on. If you cut power to the PSU, the cap will slowly drain. So when you flip it back on again, there's a huge rush of current that has to re-charge that capacitor. The RMi doesn't have an in-rush current limiting relay. Just the MOV.

Once every day or two, I'm afraid. I will stop doing it, I didn't know it was a problem. So this could be what caused the issue then?

Out of interest, does Corsair make PSUs that would not be vulnerable to this and if so which ones?

All the newer stuff has an in-rush current bypass relay. TX-M, RM, RMx (2018), etc.

 

But the RMi, HX and HXi do not.

 

I can't say that constant power cycling blew that MOV or not, but regardless of how it happened, and whether a PSU uses an MOV or relay, don't flip the thing off every day. At the very least, you're going to wear out the switch.

Thanks for letting me know, I'll be sure to bear this in mind when I get the replacement.

With modern power supply design there is a lot less problem with the grid than there used to be. The filters on the input keep internal energy from being reflected back in an out of phase manor which cause wild voltage swings.

This is why there are chokes and capacitors which are used to filter out the internal switching noise.

All you need to do is use the ATX power button to power down or even better is to use the modern standby feature which offers rapid resume.