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AverTV Studio: a shocking experience!

Discussion in 'Hardware' started by Q, May 11, 2004.

  1. Q

    Q Guest

    Was wondering if someone could give me some insight on this one. I
    currently have an AMD Athlon system with an AverTV Studio TV card which
    I use to record digital video. It´s normally plugged into cable TV, with
    a signal booster where the house cabling meets the street cable.

    Yesterday I bought an APC UPS and finally moved the PC out of the room
    it was in into another room. Previously the "wiring fault" light on the
    UPS was on, in this room it´s off, which I guess is good.

    But when I tried to plug the TV cable into the TV card, I got this huge
    blue spark, kind of like when you short a 110V line. I tried again and
    got another spark, not to mention the connector on the cable got this
    little black dent in it.

    At that time I thought my whole PC was fried, turns out it wasn´t. In
    fact nothing in the PC got fried... but when I checked the TV line the
    signal splitter was fried, and the choke (little silver cylinder between
    the internet cable line and the TV cable line) had the end blackened.

    I changed the components and tried again to plug in the cable. Didn´t
    get any sparks, but a few seconds later the cable started to get hot, I
    figure it would have been a goner had I not been able to unplug it in
    time. This test was done with no booster and no internet connection,
    just incoming street cable on one end and the PC on the other end.

    I figure the best course of action is to change the TV card, which is
    probably the culprit. If the problem was leaking current from the power
    supply (leaking into the chasis for example) I figure the PC would
    either be dead or the UPS would be blowing its circuit protector every 5
    minutes.

    But before that, two questions:

    1. What´s the electrical deal here? Before I remember I could plug in
    the cable and get no real sparks. Maybe a shock here and there if I
    wasn´t careful, but nothing else. Could the wiring fault the UPS was
    complaining about be the cause for that?

    2. Anyone else had this kind of problem with an Aver or some other TV card?
     
    Q, May 11, 2004
    #1
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  2. Q

    Jim Phelps Guest


    Hi Mario, DO NOT PLUG THAT IN AGAIN util the outlets you are using are
    checked for polarity. The Wide slot should be the Neutral (White)
    wire, the Short slot should be the Hot (Black) wire and the round hole
    is the Earth Ground, usually green if a wire or a strap to the
    mounting lug to ground to the conduit/box. If you don't have a Volt
    Meter, find someone who does. There should be 120 Volts AC between the
    small slot and the wide slot and the same from the small slot to the
    round ground hole. Luck Jim
     
    Jim Phelps, May 11, 2004
    #2
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  3. Q

    Q Guest

    Yup, everything checks out, sorta.

    At the new location neutral to hot is 115V. Neutral to ground is 115V.
    Ground to neutral is 0. Checks out with what the UPS is saying.

    At the old location is varies. Wide to small gives 115V. Small to
    round is 0. Round to wide is 60 to 80 v depending on the outlet.
    Definently something wrong there, unusual though that none of the
    electronic devices have complained so far.

    So, why'd I get the spark at the new location if the electric wiring
    checks out?
     
    Q, May 13, 2004
    #3
  4. Q

    Q Guest

    Yup, everything checks out, sorta.

    At the new location neutral to hot is 115V. Neutral to ground is 115V.
    Ground to neutral is 0. Checks out with what the UPS is saying.

    At the old location is varies. Wide to small gives 115V. Small to
    round is 0. Round to wide is 60 to 80 v depending on the outlet.
    Definently something wrong there, unusual though that none of the
    electronic devices have complained so far.

    So, why'd I get the spark at the new location if the electric wiring
    checks out?
     
    Q, May 13, 2004
    #4
  5. Q

    Jim Phelps Guest

    Hi again Mario, It does not check out OK. Round to Wide is connected
    together at the Entrance Box therefore can not show more than a few
    tenths of a volt if it is connected at each outlet properly. There is
    a difference in voltage between the two grounds hence sparks when you
    connect as the connector shells are connected to the earth ground
    (Round). The new location is not wired correctly. Probably the ground
    (round) is not connected to anything. Have it checked by a licensed
    electrician if you are not experienced. Luck, Jim
     
    Jim Phelps, May 13, 2004
    #5
  6. Q

    Q Guest

    ?
    Here goes again:

    New location:
    Round to wide -> 0
    Round to small -> 115V
    Small to wide -> 115V

    At the new location the UPS doesn't complain. But that's where I got
    the huge blue spark when plugging in the cable TV.

    The old location is where it gets screwy and I start to get voltages
    between wide and round, not to mention the UPS complains all the time
    about a wiring fault (no doubt in my mind the wiring's screwed up
    there). But there the sparks were minimal. There *were* a couple here
    and there, but nothing as intense as the one I saw recently. That's
    what's bugging me: the problem occured precisely where in theory it
    shouldn't have.

    BTW the locations are different rooms, so it wouldn't be strange if
    they were on different electrical circuits.

    Now, the wiring could have nothing to do with it... it could simply be
    that the TV card shorted internally and now sends a surge through the
    cable connector. The connector reads a short on the resistance meter,
    not sure if that's normal or not in these devices. I figure I could
    put the card back in the CPU and read voltage on the TV connector,
    normally these things shouldn't show a voltage at the connector given
    that they're the load in the TV system, right?
     
    Q, May 15, 2004
    #6
  7. Q

    Ron Cook Guest

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    Those figures are okay.
    Not a good sign.

    I'd question the design of the UPS, as well.
    Visit a Homedepot or a similar store and pick up a 'wiring tester'.
    This is typically a device with a three-prong (grounded) plug on one end and
    three indicator lights on the other end.

    The lights are marked to show correct and incorrect wiring.

    If you can find one with LEDs select it.
    The older units sometimes used neon lamps but they typically require a
    minimum of 85-90 volts A.C (as I recall) to fire.

    Call the cable company or (far preferred) a licensed electrician to check
    the cable ground connection *and* the electrical service ground.

    You're describing a classic symptom of a ground fault.
    That would be expected.
    However, even with rooms on different circuits there are standards to be
    followed in wiring.

    If your TV card shorted in a manner to cause that your computer would never
    work again.
    There is a small voltage (although I don't recall the values at present) at
    the end of the cable: no voltage, no signal.

    The fact that you have at least one receptacle that shows a voltage between
    neutral and ground (as you mentioned in another post) is enough to have an
    electrician come in and look at it.

    Remember also that if you should have a fire and the insurance company finds
    that even one outlet was incorrectly wired, you may be denied any claim.

    - --
    Ron n1zhi

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    Ron Cook, May 15, 2004
    #7
  8. Q

    Q Guest

    I decided to check and see what kind of wiring job had been done on this
    house, and came across the interesting fact that no outlet had three wires.
    All of the outlets had two wires. All except the one I had plugged into when
    the problem showed up and another one in that same circuit.

    I got myself an outlet tester and sure enough, all the outlets showed an
    open ground problem.

    So I spoke to the previous owner of the house, and he told me that the house
    didn´t have a third wire. When the house was built (about 15 years ago) the
    wiring had been done with the traditional two wires, the electrical engineer
    didn´t consider the third one necessary (don´t ask me why, he just didn´t).

    I checked with a VOM, and sure enough between computer chasis and tv cable I
    had 115 VAC... that´s where the huge spark came from. I poked around and the
    problem showed up on this particular outlet, but it wasn´t present on any
    other... even outlets on the same circuit. If I plugged in at another
    location the most I got was 5 VAC.

    So I looked inside. Upon opening the outlet I found that this one had three
    wires: hot, neutral and another one leading to the ground screw. Strange
    since the house didn´t have a third wire. So I checked the outlet voltages:
    hot to neutral: 115, neutral to ground: 115V. I unscrewed the "ground" wire
    and rechecked: chasis to TV wire was 5V.

    Seems that was the source of the problem. There was a third wire in the
    outlet (maybe part of an improvised lighting connection or something of the
    sort) and the guy who wired the outlet saw it fit to plug the third one into
    the ground lug. And what he managed to do was raise the ground lug (and
    equipment chasis) to 115VAC. It´s a wonder in 15 years nobody got hit by the
    chasis voltage. Probaly the 115V on chasis was also the reason why the UPS
    didn´t complain about a ground fault.

    After taking care of the wire, my TV card works normally again. That´s my
    happy ending to this story. Or I guess it´s more of a "to be continued" kind
    of thing... now I´ve gotta see what to do about that missing ground.

    I figure I can pull a ground wire from the breaker box through the roof and
    patch it in a non-visible location (can´t rewire that easily since the home
    is cinderblock). Or I could set up another ground-rod network on this side
    of the house and hook that up via a 0/1 cable to the original, and take the
    ground from there. In any case, it´s gonna be a job. =S
     
    Q, Jun 6, 2004
    #8
  9. Q

    Bob Day Guest

    < snip >

    I believe nearly all building codes required the third wire
    15 years ago. If that's the case with the building code in
    your area, consider suing the electrical contractor who
    installed the wiring if they're still around.

    -- Bob Day
     
    Bob Day, Jun 6, 2004
    #9
  10. Q

    Aaron Guest

    Or, if you haven't been damaged by the wiring, don't waste people's time and money.

    Aaron
     
    Aaron, Jun 7, 2004
    #10
  11. Q

    Jim Phelps Guest

    Hi Mario, In most areas of the country the conduit is a satisfactory
    Earth Ground if it was installed properly. It must go from the
    intrance box to the outlets with no breaks. The Intrance box box must
    be properly grounded to a good earth ground. If you don't have conduit
    then you will have to pull the ground (Green) wire. Outlets must be
    strapped to the conduit by their mounting straps with a wire or
    outlets with built-in grounding straps must be used. Jim
     
    Jim Phelps, Jun 7, 2004
    #11
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