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Thread: PC Issue - Grounding

  1. #1
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    Default PC Issue - Grounding

    Hi,

    Anyone know how to test for ground issues in a pc?

    I've suffered a lot of failures over the last 2 years and recently lost a firewire card.

    The manufacturer suggests a grounding issue but can't offer any advice on how to test.

  2. #2
    mixedgas's Avatar
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    Arent you guys in the UK supposed to have the green wire ground bonding test available for home appliances? Some one a few years ago was complaining about the cost as its required for commercial approval of show equipment or something?

    There is a small capacitor in PC power supplies that allows a tiny leakage to ground for safety reasons. Its called a X-cap. If that's failed, it kills stuff. If the ~380V DC in the primary part of the switching power supply is leaking through a bad transformer, that kills stuff.

    Replace the PC power supply with a high grade, high wattage supply and check the green wire ground to PC frame with a ohm meter (.1 ohms max, minus lead resistance of the test leads) Replace the power cord if there is ANY doubt. Flex the cord while checking the ground and neutral.

    Then check the house wiring grounds. In the US I'd be glad to tell you how to do this. In the UK you have ring mains, and while I know the theory, I don't know the practice.

    Steve
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  3. #3
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    Hi Steve,

    The PSU was replaced not long ago and is a high quality unit - 800W Enermax Gold Unit.

    Yes, UK supplies have an earth wire built into them it's 3 way wire supply, Live, Neutral, Earth.

    So far I've put a multimeter into the case with the +ve on the outside of the PSU casing and the -ve on the case base (that's all I could think of doing).

    All I can detect is 5mv max with a typical variation of between -1 to +3mv (meter ranged to 20v max and reading 0.05v or less).

    I think my previous issues with equipment failures - mostly LAN networking chip failures were probably solely caused by a fault in the network cable - I found no less than 1/2 the twisted pair connections not working. However, after a re-termination and re-test some weeks ago, I've had no issues since. (I discovered the virtues of a LAN tester and a 15 meter high quality telephone patch).

    So it could be that the cable was the cause of the network failures and this IEEE1934 failure is a one off and not ground related (firewire is a pain anyway). However, I just need to check as the firewire adapter manufacturer suggest it and I want to ensure there's nothing fundamentally wrong before putting a replacement card in there.

    FYI, the wider house wiring has been tested and certified within the last few years as we had a new boiler put in and it's part of the process now as H&S is very strict in the UK now.

  4. #4
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    With a men electrical system you can get funning things happening with houses near you.
    For example. if you neighbours house has had there main neutral connection disconnected then there system may still work as the neutral and earth are tied together at the the board.
    I my self have seen this. The earth in your house becomes the neutral for your neighbours house.
    It took me awhile to figure out why when I was lying on the ground working on a leaking hot water cylinder and I was getting electric shocks (even when the mains to the building where off).
    Not sure if this helps. Cool story anyways.

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