1. #1
    Deleted

    PSU hot even when shutdown?

    My old pc's PSU has been acting strangely.

    Even though the computer is shut down, when I touch the case right where the PSU is sitting, it feels warm constantly.


    What does this mean? Is it safe to leave the power switch on?


    In the last few months, I have been flipping the switch off completely. Can this damage the hardware or cause problems with the CMOS battery?

    Thanks

  2. #2
    Epic!
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    How long are you waiting before you touch the PSU? Say you have an older PSU that's about 80% efficient... If you run a 300W load, you'll actually be pulling in 375W from the wall, 75W of which will be lost as heat at the PSU itself. That's equivalent to a typical old incandescent A19 lightbulb, and you know how hot those get. It's probably residual heat since most PSUs don't have power-off fan-delay. Remember that air is a really good insulator and if it doesn't circulate, it can remain hot for quite some time.

    Yes it's safe to leave the power switch on. Some PSUs like most Silverstones and some Cooler Masters made by Enhance don't even have the physical power switch.

    Your CMOS battery has nothing to do with any other power source. It is used exclusively to keep the BIOS NVRAM in a powered state. Nor is it rechargeable if that's what you're asking.

  3. #3
    Deleted
    Thank you for your reply.


    I actually have waited for a good while on several times, and the heat persists no matter what.




    I thought that the tiny power supply that the computer drew when shutdown had to do partly with the CMOS, that's how I made the connection

  4. #4
    How hot are we talking about? If it's slightly above room temperature after the system has been off for a few hours then it's normal. But if it's hot enough to actually burn or hurt your hand then there might be something wrong with it.
    Also you said that you felt the case and not the PSU itself, so it might just be the case that's retaining heat. Have you felt how hot the actual PSU is?

    Quote Originally Posted by kidsafe View Post
    Your CMOS battery has nothing to do with any other power source. It is used exclusively to keep the BIOS NVRAM in a powered state. Nor is it rechargeable if that's what you're asking.
    Small technicality, but if it needs power it's not NVRAM Most motherboards these days use some kind of flash ram to store bios settings, and the battery is only used for the system clock so you don't have to reset the time and date on every boot.

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