hardware failure - Pc consumes 13W also when PSU is switched off

05
2014-04
  • T30

    I noticed that my pc consumes 13W also when PSU is switched off.

    So I opened the PSU and I found a yellow box directly connected with the plug's socket, before the on-off button.

    This yellow box has connected two little cables and a resistor, and it's approximately 2x2x1 cm.

    I removed it and pc seems to work properly. What could it be?

    • Answers
  • x22

    The yellow box is likely a capacitor for filtering electromagnetic interference (X capacitor).

    It can't consume 13W because it does not have large enough surface area to dissipate 13W of heat and does not have a heatsink (so it would burn if it really consumed that much) and capacitors should not consume energy.

    The resistor is used to discharge the potentially dangerous charge in the capacitor after disconnecting power, it consumes some power but it should be only a fraction of watt (otherwise it would burn).

    Update:

    Removing X capacitor may cause instability or earlier failure of PC power supply. It may also negatively affect other devices due to more interference going from the PC to power lines.


    • Related Question

    home server - Power adapters vs ATX PSU
  • Questioner

    I have a home server based on an old Pentium III 933 @ 500 MHz PC with 512MB RAM, a 60GB hard drive, two Gigabit NICs, running Ubuntu Server 9.04, and there are three network devices "supporting" it:

    • Cable modem
    • Wi-Fi router, currently used only as a wireless access point
    • 5-port Gigabit switch

    The server itself consumes around 35 Watts so the 300 Watt PSU inside has some power to spare.

    I've been thinking - would it be possible to get rid of the power adapters my external networking devices use and connect them to the ATX PSU instead?

    I know a single power adapter can take even 5-10 Watts "in idle" (when the device is not connected to it), and pretty much energy is wasted for 220v-5v conversion, so why not use the already converted energy from the PSU?

    I could configure an USB or PCI wireless adapter as an access point, but internal cable modems are pretty hard to get and I don't know if my cable provider would allow that, so I don't know if I would be able to pull it off this way. Thus for now I'm only considering getting rid of the power adapters.

    Has anyone tried that?


    • Related Answers
  • Area 51

    What you will probably find is that the external power adaptors all have slightly different voltages and output. An atx power supply only has 12v and 5v output (and 3.3 on some newer ones). So you are unlikely to get any joy from trying to wire things up.

    Your best bet may be to try and get USB powered devices as these don't need their own power bricks. But there is a limit to what you can draw on these.

    You could look at getting a cable modem with gigabit and wifi built in, that would reduce some of the clutter (do you really need gigabit at home?).

    Alternatively, if aesthetics is an issue, then hide the whole lot in the closet.