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Thread: Buzzing noise off mains, silent on UPS battery?

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    Unhappy Buzzing noise off mains, silent on UPS battery?

    Hi,

    I purchased a new Silverstone Strider Essential 500W yesterday. It seems to be running perfectly fine, however there's an electrical buzzing sound (BZZZZZZZZZ) coming from it a few times a day and the sound could last anywhere from a few mins to half an hour.

    Sounds somewhat like a fluorescent light, it's loud enough to be annoying but not loud enough to interrupt conversation. At most other times it's so silent you could hear a pin drop.



    The sound is there when the PSU is plugged in to electricity regardless of whether the PC is switched on or not, and it doesn't matter whether the PSU switch is on or off.

    The funny part is that there's NO SOUND when it's running off the UPS battery! Only happens when it's running on mains.



    My old Enermax did not exhibit such behavior, or maybe it did but it wasn't noticeable due to the loud fan.


    I have a Compaq rig in another room which makes the exact same occasional buzzing noise. It has been noisy for as long as I can remember but the PC is running perfectly fine without any problems.

    Both the Silverstone and Compaq PSUs seem to be synchronised, either both are noisy or both are silent.


    Could it be a problem with the electricity coming into my house and nothing to do with the PSU? I could get the PSU replaced but I suspect it's going to have the same noise too, besides the Silverstone is the best the store has.

    I'm just a little bit worried though so I'd appreciate your advice...


    Thanks!
    Last edited by rowertnk; 11-07-2010 at 09:31 AM.

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    If both PSU's do it at the same time, it's not the PSU's.

    When I lived in Florida, we had a lot of brown outs. Sometimes voltage would drop just enough to shut down some stuff in the house, while other times it would hover aroun 80 to 90V and stuff with wide range input capability, like a computer power supply, would continue to run, but typically with a buzzing noise.

    A decent UPS has AVR, automatic voltage regulation. What this regulation does is takes your input voltage of 90 to 150V and straightens it out to 120V.

    If I were you, I'd stick a multimeter in an open outlet and when you start hearing that buzzing noise coming from one of the PC's, check to see what voltage is coming out of the outlet. I bet it's low.

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    If it happens everywhere in the house even when stuff is turned off, I'm thinking it's bad grounding making the EMI filter grumble.

    Do you have a ground tester or a power strip with a ground indicator? A ground tester should be like $5 at your local hardware store or Radioshack-alike.

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    Thanks!

    Just to clarify things a little, the noise happens when it's running through the UPS on mains. There's no noise when I switch off the mains and let it run on the UPS battery.

    My UPS does come together with an AVR function. It is possible that the incoming voltage is low but not low enough to trigger the voltage regulation? I would have heard a click sound from the UPS if it was regulating voltage.

    The Compaq in the other room doesn't run through a UPS/AVR.

    BTW I have fluorescent lights too and I just noticed they buzz louder when the PSUs are buzzing. Probably further proof that the PSUs are fine? Circuit breaker box is silent and nothing erratic from other appliances such as the TV. Lights aren't noticeably dimmer either.

    Perhaps it's happening when there's higher demand for electricity? I think I'll note down the time when the buzzing happens and see if there's a correlation. Right now its the low demand hours and I haven't heard any buzzing for around 2 hours.

    Or could arcing happening somewhere between the substation and my house cause the buzzing?


    TheSlakey: Thanks for the suggestion. I doubt it's bad grounding but I'll try the ground tester if I come across one.

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    I'd worry about a ground fault. When running off a UPS, the power supply is isolated and there's no way to form a circuit to the PSU case and ground pin, but when running off AC, if there's something wrong inside the PSU, it could arc to the case.

    A GFCI/RCD would trip instantly if this happened, so plugging the computer into one would be a simple test.

    But check JG's suggestion of a brownout, too. I remember an earlier question about one room with particularly low-voltage outlets. If you're losing a lot of voltage between the fuse box and the outlet, then something in the walls is getting hot and should be fixed before anything catches fire!

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    Guys I bought a multimeter and tested. Voltage in both rooms is about 235 - 245, fluctuating at times and steady around 240-241 at other times. (The voltage here is 240V)

    Neutral to earth is about 5V, Live to earth gives about 235V. Same in both rooms. I'm not sure how to interpret this data so I'll need your help on that.

    At many times when the hot water shower is on, the buzzing starts.



    Reading in the Silverstone room (shower is on in other room):
    Try 1: 265 - 270 (buzzing!)
    Try 2: 250
    Try 3: 240
    -----------------
    Reading in the Compaq room (shower is in this room and on):
    Try 1: 250
    Try 2: 235
    Try 3: 240

    Compaq room - load with AC, fan, lights, shower on
    Try 4: 235V

    AC off
    Try 5: 237 ~ 239V


    I don't think GFCIs are available here but everything in this house is connected to a circuit breaker panel and then to a RCCB. RCCB is quite a sensitive one, trips often when there's lightning.

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    UPDATE: Buzzing just started even with shower and everything else off!

    Silverstone room : fluctuating between 233 - 243 V

    Neutral to ground : 3V

    Live to ground: fluctuating between 231 - 240V


    Tried again.

    Silverstone room : steady 237 ~ 238

    Neutral - ground: 4V

    Live - ground : steady 235 - 237


    Compaq room : similar readings.


    PCs in both rooms still buzzing.


    --------------------

    Tried switching off everything in the house except the Silverstone PC and the fridge downstairs. = Buzzing

    Switched off everything except the Silverstone PC = silence

    Switched everything on again = silence.


    This is getting too random and weird.

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    Silverstone gives for the input voltage of the Strider Essential 500W an input voltage of 103.5V~253VAC. Anything over 253VAC would be over spec, and that would explain the buzzing as the PFC circuit is forced to work out of spec. This I would definitely call harmful.

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    Buzzing started again.

    Silverstone room: fluctuating 226 - 231V

    Neutral - ground : 4V

    Live - ground : fluctuating around 226 - 230~1



    It's within the Silverstone specs...


    ------

    3 mins later the buzzing stopped. But the voltage is still the same, fluctuating between 224-232
    Last edited by rowertnk; 11-08-2010 at 06:29 AM. Reason: Update

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    Bad grounding.

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