Static Electricity or Small Amount of Current?

By ahnadahodo
Nov 22, 2004
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  1. Hello, :)

    I recently built my first PC from "scratch" and have a question about something that happened while I was working on it.

    The situation occurred after I had everything installed and I had gone back into the case to do some more work. I was wearing an Anti-Static strap so as not to fry anything. Several times while I was working inside the case, I brushed against the case and was met with a slight jolt of electricity. After the first time or two, I brushed against the case intentionally to see if it would do it again, it did. I had absolutely no power cables connected to the components, so this puzzles me. It didn't "snap" like static electricity, but felt more like a constant current flow.

    Is it possible that there was some sort of stored electricity inside the power supply, which is where I had my static strap connected, that was released when I completed the circuit by touching the case?

    I'm just curious because it doesn't seem as though there should have been any current flow considering that there were no power cords connected.

    Thanks in advance for any replys,

    ahnadahodo
  2. howard_hopkinso

    howard_hopkinso Newcomer, in training Posts: 25,948   +19

    Yes it is possible for power to be stored in the capacitors of the psu.

    Regards Howard :grinthumb
  3. ahnadahodo

    ahnadahodo Newcomer, in training Topic Starter Posts: 56

    Thanks Howard,

    Another question:
    Since there's stored power in the power supply, is there a better place to connect my anti static strap?

    ahnadahodo :D
  4. howard_hopkinso

    howard_hopkinso Newcomer, in training Posts: 25,948   +19

    If it were me I`d just connect the strap to the case.

    Regards Howard :D
  5. Per Hansson

    Per Hansson TS Server Guru Posts: 1,930   +123 Staff Member

    You should have the power cable attached to your PSU but the powersupplies on/off switch set to the off mode, this way your computer is grounded... (Because you do have proper ground cabling in your house don't you?) ;)

    Next you should connect your wrist strap to any ground, be it the ground outlet in the power socket or the computers chassi...

    I've done some work trying to repair a dead 9800XT GFX card after someone did a bad job at a volt mod on it... (I bought it dead from the guy...) Let me just tell you that _allot_ of things depend on proper grounding in a PC so don't run it with a floating ground! (sorry to go a bit OT..)

    I have a friend that don't have any grounding for his PC in the room it is in... I have been telling him for years to ground it properly... Right now if I touch it and a ground point (just a big metal object..) I get a real big zap from that computer... And it does not stop at that, i.e. I do not instantly discharge it because so much electricity has built up in the chassi that my body mass can not transer it over the the other ground point (in this case it is a radiator...)
  6. ahnadahodo

    ahnadahodo Newcomer, in training Topic Starter Posts: 56

    Per Hansson,

    Thanks for your reply.

    I guess it never dawned on me that I should keep the power cord connected for that reason, but it makes sense now that someone actually said it. :haha:

    A question though, what do you mean by "floating ground", that's a term I've not heard before? :confused:

    Talk to ya' later,
    ahnadahodo
  7. Per Hansson

    Per Hansson TS Server Guru Posts: 1,930   +123 Staff Member

    By floating ground I mean a system that is not connected with a ground cable to the ground itself

    This system will still use the ground, leading to an ever increasing voltage and current stored in the computers chassi, therefore referred to as floating... Since the current has no where to go it just "floats around" the voltage can actually be very high, in the ten of thusands volts, but fortunantley the current should be very low as long as everything works within spec so the most dangerous thing you might get is a shock similar to touching your car when you are charged with static electricity, the only difference being that now you become charged with electricity, not the other way around as it is when you touch the car....

    On the flip side of the coin if something in your computer was misbehaving, like the powersupply, your computers chassi could contain the same current as the power outlets current, which could kill you, again a proper ground system would in this case shutdown the power to your entire house...


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