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Power

PC Not Booting Until a Different Phase is Used? 130

Posted by Cliff from the mysteries-of-the-server-room dept.
2by4 asks: "I run at IT Dept for a small firm, our network room houses production & development servers. Some machines are plugged straight into a strip with no UPS. Here is the Mystery Problem: When the power glitches, the strip machines go down, and some of these machine WILL NOT come up again until I switch them to a new outlet. Once this happens, I can put them back on the original outlet and they will work. Unplugging & replugging on same outlet is not enough. I have seen this on at least 5 machines so far, with independent confirmation. We can narrow the 'fix' to plugging into an outlet of a different phase (there are 3 separate 120v phases powering the room). The symptoms vary from no powerup, to frozen at the BIOS (depends on motherboard make), etc, but consistently, switching to a new phase fixes them. I tried the 'unplug-wait-&-replug' cycle, to no avail. Using a new outlet w/ a different phase is the only solution. Any theories? I assume the new phase is causing something to 'reset', but what? I can provide more details, but I am wondering if anyone has seen this before? I am completely and absolutely stumped. Our power is healthy, lightly loaded, evenly distributed and the power strips are new. I know I should have at least a simple UPS, but this mystery is causing me to lose sleep."
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PC Not Booting Until a Different Phase is Used? More

PC Not Booting Until a Different Phase is Used?

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  • Hmm (Score:5, Insightful)

    by pclminion ( 145572 ) on Tuesday January 17, 2006 @02:34PM (#14492255)
    Have you tried shorting the two power pins of the power plug together? Just tap'em simultaneously with a screwdriver. Maybe a capacitor inside the power supply is charged up and somehow it's blocking the flow on a different phase. If so, it's crappy engineering.

    Obviously, I mean that you should do this with the plug UNPLUGGED.

    • Re:Hmm (Score:3, Informative)

      by hey! ( 33014 )
      Well, once the plug was unplugged from its socket, how does the capacitor remember what phase it was plugged in? It's just sitting there holding a DC charge, which of course has no phase to rememeber.

      I generally have the same problem with this entire scenario. If the equipment is designed to work on one phase, once it is disconnected from the wall, how does it keep track of exactly where the sine way should peak? The only thing I can imagine is that there is a battery driven oscilllator whose phase is s
      • Well, once the plug was unplugged from its socket, how does the capacitor remember what phase it was plugged in? It's just sitting there holding a DC charge, which of course has no phase to rememeber.

        Not if there are two capacitors, one on each phase. One might be in a charged state while the other is discharged, that would allow the two states to be distinguishable. It would also depend on the exact moment that the power got dropped. A diode would probably have to be involved somehow. But this is just a

        • Re:Hmm (Score:1, Informative)

          by Anonymous Coward
          I worked as an electrician for a time (doesn't pay as much as programming, though :), and sometimes wierd problems can be traced to "loose neutrals". If you could open up a circuit-breaker box, you will see either 3 or 4 main "power" wires, distinct from the ground wire. 2 or 3 of them are actually your power lines, which feed the breakers (you have described a 3-phase system, so you must have 3), while the remaining line is the "neutral". Its purpose in a SINGLE-phase system is to return all the power b
          • One a side note there is no two phase power used for distribution today. The proper term your lookig for is called a 3 wire single phase system (120/240 volts).

            Now as for 2by4's problem:
            Sounds like you have some bad power supplies that are acting up. It is a possibility that that particular phase might have noise on it or "dirty power" caused by other equipment or wiring problems. Some buildings have 277/480 mains(or sometimes in canada 346/600) and then have seperate stepdown transformers throughout the bu

        • Re:Hmm (Score:4, Informative)

          by Neon Spiral Injector ( 21234 ) on Tuesday January 17, 2006 @04:16PM (#14493207)
          My machine at work gets wonky after a power blip. It will not power up until I remove the plug from the wall (or flip the main switch on the PS) and hold the power button on the front of the case. I can actually hear a little squeak from the power supply that lets me know it is ready to go.

        • Re:Hmm (Score:2, Informative)

          by Trepalium ( 109107 )
          I suggest you learn how power supplies work. At their most basic level, [electronic...orials.com] they consist of a diode and a capacitor. You will not be able to discharge the capacitors by shorting the pins of the PSU because of those diodes. It's far easier to discharge them by removing power from the computer and attempting to power it on.

          I'm not an EE (and only have the absolute basic knowledge of electronics), so I can't really meaningfully elaborate further.

          • I suggest you learn how power supplies work. At their most basic level, they consist of a diode and a capacitor.

            And an inductor and a switching transistor. I'm not ignorant.. Even built one, once. I was guessing that this particular supply might have some extra circuitry between the wall and the rectifier, possibly for cleaning up the AC waveform. Again, it's a wild-assed guess. Other people have put forth more likely scenarios, involving faulty grounds.

    • Hmm-Willy Watt says... (Score:1, Funny)

      by Anonymous Coward
      "Obviously, I mean that you should do this with the plug UNPLUGGED."

      Man! You're just trying to take all the fun out of electricity, aren't you?
    • I think this is the winner. Your PC Power Supplies are holding a charge (in one of the caps) and when you plug them back in, they are unstable and won't boot.

      When you move them across the room, you've given them adequate time to discharge, and they will power up.

      Try waiting for a longer time before plugging it back into the same outlet. I doubt it's the outlet/phase wiring. I think the culprit is your PC PSU's.

      Gateway's were notorious for this - leave them unplugged for a period of time, and they would s
    • NEW != work correctly. Just because you bought something new doesn't mean it can't be the cause of your problem. Did you actually swap strips?
      Healthy != glitchy If you had healthy power, you wouldn't be losing it.
      It sounds like this only happens when you lose power. Correct? Is it a blackout, glitch, or brownout?

      You have 5 computers that display these symptoms. What do they have in common?
      Same circuit? Same powerstrip? Same outlet on strip? Same model of server? Same PSU? Do you put the problem computer bac

    • Re:Hmm (Score:2)

      by EvlG ( 24576 )
      OMG this totally fixed a dead machine I have here.

      Thanks for the tip!

  • CB (Score:4, Insightful)

    by twoflower ( 24166 ) on Tuesday January 17, 2006 @02:34PM (#14492257)
    Try resetting the circuit breaker on your "strips".

  • Gateway (Score:4, Interesting)

    by gmerideth ( 107286 ) <gmerideth @ u c l n j . c om> on Tuesday January 17, 2006 @02:34PM (#14492266) Homepage
    We had a customers Gateway machine that often did that exact same thing. Machine would refuse to boot or crash at the BIOS with invalid memory errors. Swapping the outlet to a plug across the room would cause the machine to boot just fine and stay running for months on end. Even moving the plug back to the original outlet would be fine for a while. The kicker is, it wasn't just the computer. Plugging in his palm would cause the palm to reset while sync'ing and glitch during regular use.

    Our Fluke meter showed nothing special on the line and an APC UPS showed no spikes nor higher than normal voltage levels.

    To this day we call it the haunted outlet and tend to just keep things away from it.
    • Using a DVM to monitor the line won't give you much beyond a short-term average voltage, and it may not even do that if you're using it incorrectly.

      Having trouble with the Palm also makes a pretty strong case for it being the outlet or wiring to it. Try replacing the outlet and check for tight connections on it and all nearby outlets.

      There are a number of local problems one can have with power, in addition to those coming in from the outside world.

      1) low-voltage condition under load
      If there is a high-resis

  • HUH??? (Score:2, Interesting)

    by voxel ( 70407 )
    "Mystery Problem: When the power glitches"....

    then you say:

    "Our power is healthy, lightly loaded"...

    Not contributing to the solution of your problem, but my office doesn't get "regular" giltches like yours seems to, even though our power is "healthy" too.

    Sounds like you need to call your power company.

    • Re:HUH??? (Score:3, Insightful)

      by Nasarius ( 593729 )
      Sounds like you need to call your power company.

      More likely a competent electrician, if some of the outlets are fine and some aren't.

  • As an EE student, my professional opinion is: (Score:5, Funny)

    by Anonymous Coward on Tuesday January 17, 2006 @02:35PM (#14492269)
    Gnomes?

    (Flunking, in case you couldn't tell)

  • Bad ground (Score:2, Interesting)

    by Anonymous Coward
    Test the ground line on the power strip.

  • Are you sure your power is all the way recovered? (Score:5, Insightful)

    by argStyopa ( 232550 ) on Tuesday January 17, 2006 @02:40PM (#14492317) Journal
    You mention when your power 'glitches'...brownout or blackout or spike?
    We are a light industrial building in a heavy industrial park, and I swear the power goes glitchy 2-3 times per year.

    We'll get brownout and blackouts, and when the power comes back it SEEMS like it's on, but only 2 of the 3 phases of the A/C actually comes up, meaning (depending on how it's wired at the *circuit box*) some circuits are dead, some are full, and some are semi-brownout (our flourescent ballasts LOVE that half-state.....not).

    That third phase sometimes doesn't come back up for hours.

    I have no idea if this is of any help, that electrical stuff is arcana to me, I'm just reporting what we've discovered.
    • Had this problem in my parent's house TWICE. The first time was that over 20 years of use, one leg of the mains had worked it's way loose from the screw holding it to the main switchbox. The second time was a halfway blown transformer on the pole. Didn't even think of this as a possible problem for TFA until you said something.
      • Your parents must have very very unusual power. Three phase power is hardly ever found in houses. In the US, we don't even have two phase power - we use a single split phase.
        • It was two phase- did I say anything different? But the result is the same- the circuits on the phase that was blown on the transformer or the phase wire that had worked it's way loose went out, or rather browned out, while the other phase stayed good.
          • The original posted said that 2 of the 3 phases would be on, and the 3rd phase would be down. You said you had the same problem, so actually yes, you did say something different.

            Also, if you are in the US, you've got single split phase. If you're in Europe then you have two phase. Are you sure your parents have two phase? How much do they pay for that?
            • Also, if you are in the US, you've got single split phase. If you're in Europe then you have two phase. Are you sure your parents have two phase? How much do they pay for that?

              In Oregon, two phase is common (I know, I use X10 in my house, and have problems with the 5v powerline commands getting from one phase to the other). Two 110V wires coming in from the transformer. In the case of the X10 problem, a simple capacitor across the phases (passive coupler in a box behind my dryer- one of the few places I
        • in the US almost every house if not every house has 2 phase current for the 220 outlets powering heavy appliances such as washers, driers and dishwashers. Commercial and industrial facilities get 3 phase and get higher voltage connections used for heavy equipment.

        • In the US, we don't even have two phase power - we use a single split phase.

          Um, Wrong.

          We definitely have the power, it may not be universally connected residentially.... If you have 220 in the house (typically for an electric stove or a clothes dryer), you have two phase coming in from the street.

          You may also have multiple phases coming in if you have a higher load. This office is that way.

          The multiple phases may not be wired, but they are definitely available. I looked into setting up a 3-phase circuit t

          • If you have 220 in the house (typically for an electric stove or a clothes dryer), you have two phase coming in from the street.

            Not really. House 240V power is created by connecting one phase of a three phase feed to a transformer with a center tapped output. The center tap is grounded and voila, you get split phase 240V power. It consists of a ground, plus one leg at +120V and the other at -120V, referenced to ground of course. Take the potential across the two of them and you get 240V. While these legs ar
          • I have a friend that has 3-phase to his house as well. He had to pay an arm and a leg for it because his neighborhood just had a single phase delivery since it was residential, and residential is based on a single phase power. Yes, most residence are single phase power. While it is true there are two seemingly different phases that give a potential of 240 volts between them, that is still one phase. It's called Split Phase [wikipedia.org]. The fact that the differential voltage is exactly twice normal voltage is how y
          • If you've got 220, then you most certainly have your power coming from a center tapped transformer coil. That's a single phase, and you get 110 volts if you hook up one side or the other to the neutral. 220 comes from the two hot wires.

            Check Wikipedia.
        • I live in an apartment building that has three phase power. Some of the circuits are connected to one phase, the rest are connected to another phase. On occasion, one of the phases will fail and I will lose roughly half of my circuits until the power company shows up and fixes the problem.

  • The true Mystery (Score:2, Insightful)

    by wift ( 164108 )
    ... is why you continue notto have a UPSs after several brownouts.

    I think starting the article with "We have since gone out and bought some fairly inexpensive UPS's to eliminate this problem but nonetheless the phase detection has piqued my curiosity ...."
  • Unplug the machine, hold the power button for about 10 seconds, plug it back in. You really don't want your machine bouncing on/off during power problems. Either that or go get a cheap UPS.
    • This comment needs more attention. Look at the larger picture here. You have identified a solution without identifing an issue. You say the solution is to change "phases." But what is the problem?

      My first reaction to the parent question is what do you mean by "different phase." Do you mean your server room is fed off of 2 or 3 phase power? And that some outlets are fed off of different branches? Or do you mean you change to a different circuit?

      What is likely is that certain voltage rails aren't settl
    • Comment removed based on user account deletion

  • What Would Jordi Do? (Score:4, Funny)

    by Akito ( 222802 ) on Tuesday January 17, 2006 @02:51PM (#14492425) Homepage
    Did you modify the phase variance?
    • Good idea, though I suspect
      the problem is really in the flux capacitors.
    • Did you modify the phase variance?

      Alternatively, try modulating the frequency of the deuterium drive. If that fails, try reversing the polarity of the neutron flow--you'll need a sonic screwdriver (like $10 at Home Depot/Lowe's). If that fails, your dilithium crystals are probably dead and you'll need to find replacements (should take about 60 minutes, minus commercial breaks--you'll need someone in a red shirt to help you, best if it's not a close friend).
  • Have you measured the voltage on the outlets when the computer is not working? . Anything below 100 will not work. If one of the phases is overloaded and thus your circuit not balanced, you'll have a serious voltage drop on the outlets of the overloaded phase.
    • Not always true...

      We were having brown outs a few years back and my PC ran just fine with no glitches, even when I measured voltages as low as 90 volts.

      Not to say that more robust server class machines will do the same, but I imagine at least some of them will... especially for the varying definitions of what class of hardware belongs in a machine room.

      -Steve
      • Success (Or lack thereof) will depend deeply on the power supply. If you have a big beefy power supply that is much more than the machine needs, then it likely won't be as big a problem than if you are running a power supply close to the required level for the load in the system.

        The thing is, when a power supply is running on low voltage, it has to make up for the lacking by drawing more current. This also stresses the power supply components as they have to do more work. Many power supplies will not o

  • Check the Neutral To Ground (Score:5, Informative)

    by getagrip ( 86081 ) on Tuesday January 17, 2006 @02:56PM (#14492473) Homepage
    We just got a 30 amp circuit installed for a 3kv ups. The UPS once powered up had a "check building wiring" light on the back that came on and stayed on. The cheapy circuit tester indicated that the wiring was fine along with an electrician verifying that all the wiring from the panel to the outlet was correct. One more symptom of this area is that light bulbs blow out much more than normal, although the PCs have not had anything unusual happening.

    We had the original electrician who installed the line back out to test. His voltmeter was showing about 20-30V between the neutral and ground. According to code (IANALE), these lines are supposed to be connected at the panel. Apparently without this connection, the two sides coming off the transformer can float in the voltage which may have been responsible for the light bulbs blowing. Once the neutral and ground were connected, the wiring fault light went out on the ups and everthing has since been fine.

    SHORT RESPONSE: Have a licensed electrician check out your circuits.

    • Re:Check the Neutral To Ground (Score:5, Insightful)

      by sakshale ( 598643 ) on Tuesday January 17, 2006 @03:11PM (#14492613) Homepage Journal
      SHORT RESPONSE: Have a licensed electrician check out your circuits.
      Amen!

      I actually worked on a system where printer interfaces were burning up because an electrician had reversed neutral and ground in the outlet where the printer was plugged in. There was enough of a difference between neutral and ground to damage the interface of the computer.
    • Mod this post up; "getagrip" is correct. You have a partially lifted neutral. An electrician must fix it and now.
    • Just an FYI to the parent and also the poster, you can buy a 3 prong electrical line tester from Home Depot or any hardware store for under 10 bucks, which has 3 or 4 LEDs on it, that will tell you exactly what, if any, wiring is wrong in the outlet.

      I found this indespensible when I was shopping around for a house - you never know what you will find in a house that has bad wiring. Always bring a tester, can sometimes save you from wasting money on a home inspection.

      • I'm not sure that would have helped. Note the grandparents mention of the cheapy detector saying everything was fine. I read that as being one of those things with the 3 lights. Those only really help with obvious stuff, like open circuits (On any wire) or reversed wiring. I don't think it would show anything abnormal where the neutral and ground wires were both connected, but not properly wired at the box as mentioned in the grandparent.
        • you can check something like that yourself with a multimeter, though if you didn't already know you could i wouldn't recommend trying it.
        • You are absolutely correct. I went to home depot, got the cheapy yellow tester with the 3 leds and plugged it in. It indicated everything was fine. But the 3kv ups still had its wiring fault light on. So I take that to mean that the little testers will find really bad faults but not more subtle ones. The building I am in is over 100 years old and used to be used for manufacturing. The transformers may have been wired a bit differently to supply power to the three phase motors and thus, were not wired 100%
    • Just a note - "connecting the neutral and the ground" does NOT mean you should short the neutral to the ground at the outlet. Doing so would be a good way to melt wires and start fires. Get an electrician to fix the problem.
    • "We had the original electrician who installed the line back out to test. His voltmeter was showing about 20-30V between the neutral and ground. According to code (IANALE), these lines are supposed to be connected at the panel."

      Depends on what you mean by panel.

      The "ground" (the green or bare wire, which under normal conditions carries NO current) and the "neutral" (the white wire, which DOES carry current in a 120 Volt circuit and should be assumed to carry current in all others for safety's sake) must be

    • SHORT RESPONSE: Have a licensed electrician check out your circuits.

      Absolutely! By doing that, you found and fixed a genuine safety hazzard.

  • ALL devices and connections to the same ground (Score:3, Informative)

    by Futurepower(R) ( 558542 ) on Tuesday January 17, 2006 @03:03PM (#14492527) Homepage
    As someone already said, when you have weird electrical problems, suspect the ground. Remember that ALL devices and connections on a computer system need to be connected to the same ground. The exception to this is Ethernet network connections, which are very well isolated.

    Printers must be connected to the same ground, for example. Check the integrity of the ground; their should be low resistance, as measured with an ohmmeter after you have turned off the power, of course.

    Also suspect that there is some weird voltage riding on the power. Is your power clean? The only way to check this is to look at it with an oscilloscope. Oscilloscopes make an instantaneous on-screen graph of the voltage.

    All computers should be connected to battery backup power supplies, too of course.
    • Ground is shared by all 3 phases. I've measured between neutral & ground & hot & ground on each of the 3 available phases (at the outlet & breaker box) and all is well. The Home Depot circuit tester shows all ok as well. I have not used an oscilloscope on it, that may yield some interesting clues. I shall try that. (I'll have to haul my museum piece of an oscope into work for that one). Thanks.
      • Something sounds as though it needs to be investigated. Generally, three phase power is for industrial uses, in which noise and small fluctuations don't matter.

        Certainly all computers must be plugged into a battery backup power supply. The loss of data is far more expensive than the $20-after-rebate cost of a UPS. If Windows XP writes garbage to its registry file, it can be impossible to recover cheaply.

        Sometimes PC power supplies don't reset from an error condition until they are unplugged for a minu
    • The exception to this is Ethernet network connections, which are very well isolated.

      Nope, no exception. It's quite important to make sure equipment connected via electrical ethernet has common ground.
      • Not sure if you realize this, but Ethernet over copper is not referenced to ground. Look on any NIC, the RJ-45 jack is connected to an isolation transformer. I'm not saying establishing common ground is not a good thing to do, I'm just pointing out something you may not have been aware of.

    • Seconded. I have a PC here which, after a mains glitch, sometimes fails to start, even after disconnecting the PSU from the mains for a whole day, or even disconnecting the PSU from the motherboard.

      The last time this happened, I disconnected the PSU from the mains and the motherboard and reluctantly started stripping it for parts. Whilst removing the AGP graphics card, the motherboard-mounted LED to warn that the motherboard still had power started flickering on and off (eek!)

      I hurriedly started yanking

  • Phase balance? (Score:4, Informative)

    by redelm ( 54142 ) on Tuesday January 17, 2006 @03:04PM (#14492538) Homepage
    Three-phase power is kinda screwy and needs to be kept balanced. Is the high-drawer that justifies three-phase running during these restarts? If one leg is overloaded, it can get dragged down and the return path overloaded. Check your neutrals, grounds and voltages.

  • Just Happened to Me (Score:3, Informative)

    by mlmitton ( 610008 ) on Tuesday January 17, 2006 @03:05PM (#14492558)
    Boy, talk about the long arm of coincidence. This just happened to me *last night* with my Replay TV. It wasn't showing any life whatsoever, but I checked other devices in the same outlet and they were getting power. So I figured the Replay TV was cooked. I pulled it out, and thinking I might try and fix it (i.e., kick the damn thing a few times) I plugged it into a different outlet and it worked just fine. I took it back to the original outlet, and it works just fine. This hardly answers your question, but another data point never hurts.
    • Replays sometimes get touchy about booting. See AVSforum.com for examples. Often, this is due to either a) the drive starting to die, or b) the power supply is starting to die, or c) the IDE cable is loose/bad, or d) the power connectors between motherboard and PS are arcing/glitchy/resistive (this has been seen a number of times, often with discoloration).

      If it gets really bad, and a different HD doesn't fix it, there's someone who repairs them as a business who's on avsforum all the time, and also sells
  • If power's coming and going that often you need something. As well as handling short power-outs without any problems, even the consumer-level ones can provide some monitoring of the input voltage. If you're having trouble getting the cash signed off, "I can't start this machine without it" should help.

    However, it does sound though like you need to get someone competent to check over the electricity supply. I'm not, and neither are you. I'm assuming that you're in the US (from the 120v comment) and I'm s
    • Usually 3 phase outlets are completly different looking plugs. If that is the case. It could be that the a phase is on one side, and b phase is on the other side of a panel. I would go along with what other people have said. Power will get you without out you knowing. If you know what you are doing. Make sure the all the phases are good and tight. Especially the neutral. If you are using 3 pahse, you might read up on it a bit. That would make sense. (If you havent already). IF you have an electrician co
  • This happened to me once with my old Suse box. The really strange thing was that it's plugged into the same outlet as my other computer, and it didn't seem to have any problem at all. After it started working again, I just wrote it off as one of those things beyond my comprehension. Useless, I know, but at least you know it's happening to people on the residential end.
  • Something very similar happened in my Mom's condo, with two different 65W PowerBook power adapters. They would stop charging the 'Book whenever the paper shredder was turned on. In order to get them to work, they'd have to be plugged into a different circuit... then we could plug them back into the original circuit and they'd work OK until the next shredder use.

    Ultimately, both of them quit working altogether. IANA[electrician] and she didn't feel like hiring one, so I just got her another adapter and she

  • Drain the Power Supply safely. (Score:5, Informative)

    by cravey ( 414235 ) * on Tuesday January 17, 2006 @03:14PM (#14492647)
    I've run into this type of issue several times. The issue is'nt so much moving the plug, it's that the MB maintains power for up to a couple of minutes after the power is lost. If the Power glitched, the MB may be in a non-useable state. The way I solve the problem is this:
    1) Unplug the Power supply.
    2) Hold down the power button (on the front) for 10 seconds.
    3) plug in the power supply
    4) Turn on the computer.

    I solve this issue with most of my systems by connectiong them to a UPS. Some crash on their own so often that they're not worth a UPS.
    • I was going to start my own post but my experience kind of relates to what you have said.

      Here at work I have noticed that when some older IBM machines don't power on properly..

      I unplug the power cable from the back of the machine and wait 30 seconds, the power supply makes a kind of discharge sound which hard to explain but you'd know it if you heard it.

      Then we just plug the power cable back in and the machine powers on without delay :-)

    • My UPS is such a POS that when I shoot my USP in CS:S it FUBARs my CPU, then some AWP whoring FNG gets a HS on me when I am practically AFK.

  • Sounds like it could be a grounding problem (Score:4, Insightful)

    by relifram66 ( 899283 ) on Tuesday January 17, 2006 @03:23PM (#14492724)
    This sounds like it could be a ground problem. I'd check (if you have the capability) the hot-to-ground and the hot-to-neutral with an oscilliscope on the effected outlet. Barring that you can check it with a multimeter, you may find that the neutral or the ground is inductively coupled to a hot phase.

    Some other things to check:

    The continuity between the outlet and the electrical box (all three wires).

    That your grounding rod is correct for the type of soil in you area.

    A different power supply.

    Also, like a previous poster noted, try shorting the input to the power supply (when it is unplugged), that may give you a temporary fix.

    • O-Scope Warning !!!! (Score:2, Interesting)

      by fluffy99 ( 870997 )
      If you opt to test the outlet with an O-Scope, first find out if the ground pin on the cord is tied to the ground on the o-scope inputs and chassis! Most analog, corded models are and you run the risk of putting 120-volts on the chassis or shorting the outlet through the o-scope. More than a few amateur electronics techs have missed this feature and blew up an o-scope or shocked the hell out of themselves. Electronic techs often use isolation transformers to protect the equipment and themselves for this
      • you run the risk of putting 120-volts on the chassis or shorting the outlet through the o-scope.

        Also note that oscilliscopes typically have very high-impedance inputs, that will work perfectly well with some megaohm resistors in series with the test leads. Worst case, it may show a lower amplitude wave, but the waveform will be preserved. At 377V (peak to peak voltage for 120V RMS), the most current you can pump through a 1 megaohm resistor is 377 microamps, which should be safe.

        And of course, make sure

  • Grounding problem and testing (Score:3, Insightful)

    by WasteOfAmmo ( 526018 ) on Tuesday January 17, 2006 @03:26PM (#14492752) Journal
    As a couple of others have pointed out:
    • you may well have a grounding problem either on the strip or the outlet that the strip is plugged into.
    • when a computer is in the "won't work on this strip" state: unplug it and ground each of the 3 terminals momentarily. You can do this by simply touching all three prongs to the metal face plate of a switch or plug. (this is similar to the suggestion that someone gave about shorting out the prongs with a screwdriver but better). Then try the computer. If this works then you may have a floating ground on the strip or somehow voltage is getting induced onto the ground.
    • you can buy a simple tester to test the wiring on a duplex plug. Home Depot usually caries them for less then 10 bucks. The plug into a 3 prong outlet and have 3 lights on them (2 orange and a red if I recall correctly). Depending on which lights light up tells you about the wiring and suggests what the problem is. I have even found high resistant neutrals and other such strange wiring problems with it.
    Of course once you have tried this (or not) and have a better idea where/what the problem is, it is time to call a qualified electrician.

    Merlin.

  • Bad Power (Score:3, Interesting)

    by Renraku ( 518261 ) on Tuesday January 17, 2006 @03:28PM (#14492771) Homepage
    There should be some kind of inline tool that measures the 'quality' of the power coming from the line and flowing into devices. It could have like 5 levels or so and you could check the outlet for problems during real-time use. It could have a bunch of different functions, you know, like checking for electrical problems at the same time.

    Unclean power is the problem that causes more crashes than people would like to admit. I've had my parents on the other side of the house start a vaccum cleaner and I've bluescreened at the same time..quite a few times..before. Obviously not a coincidence.

    • Re:Bad Power (Score:4, Funny)

      by TeknoHog ( 164938 ) on Tuesday January 17, 2006 @03:37PM (#14492865) Homepage Journal
      I've had my parents on the other side of the house start a vaccum cleaner and I've bluescreened at the same time..quite a few times..before. Obviously not a coincidence.

      Obviously, your electrical system can only support a finite amount of suction at a given time. Consider switching to an OS that doesn't bluescreen ;)

  • It will not come up after being powered down. Haul the damn thing into the lab, turn it on, works fine. Haul the damn thing back to the printer station, comes back on ok. Power is fine at the printer station. Laserjet 5000 at printer station does not have the same problem. Other Laserjet 4000's don't have the same problem.

  • I had a weirder one (Score:1, Interesting)

    by JohnnyGTO ( 102952 )
    Seems that every computer connected to this old Thinnet network would eventually fail, either the motherboard or the network card. I found out the hard way if you grounded yourself to the case you got a good 70vAC shock!!

    After a bunch of head scratching I tracked it down to one PC plugged into a floor outlet. Seems the outlet was cracked and had a carbon trace from the Hot to the Gound on its face. Got 4 year support contract with an AZ tribe for finding that one :-)

    • I've experienced a similar situation. When I worked for a school district, we had a computer lab that the computers were plugged into power strips that were plugged into outlets in the floor (the computer lab was originally the sewing machine room of the home economics classroom.) When we were working on the computers we discovered that the tables were slightly "charged". Apparently, the wax that the custodians used on the floor over the years turned out to be a halfway decent conductor. We moved the co
  • Spooky stuff like this is usually bad grounding. The machines in question are connected to each other, right? (network? serial port? some such...) and the ground voltage is different, causing current through the system when the others are up but its power is off.

    I'd look into the docs on the UPS you have to see if there is a way to hook up a ground lug on the *output* side of the UPS to tie it to building ground. I'd also get one of those testers over at Home Depot to see if your outlets are all actuall

  • The List (Score:4, Informative)

    by Ed Almos ( 584864 ) on Tuesday January 17, 2006 @05:35PM (#14494143)
    1) As other have pointed out, bad grounding on one or more phases.
    2) Bad neutral on one or more phases.
    3) Voltage drop on one or more phases.

    For the first three get an electrician out, don't mess around with three-phase power.

    4) Electrical noise on one or more phases, this may not be caused within your computer room.
    5) Equipment connected on different phases affecting each other, for example a printer on phase A and a server on phase B.
    6) Borderline power supply in a machine affected by one or more of the above conditions.
    7) Faulty power strip(s).
    8) Incorrectly wired plug(s) or socket(s).

    Ed Almos
  • Buy or rent a power quality monitor, such as those from Dranetz. You probably will find your power isn't as clean as you thought, or your building is wired wrong.

  • I would venture that the problem may be a bad ground on one circuit. I have seen problems where a computer plugged into a peripheral, say a printer, would crash if the peripheral was on a different power circuit, due to a problem with ground and neutral not being connected (or something like that).

    It's been a long time since high school electronics, but I could see a grounding-related problem more simply than a phase-related problem.

  • I concur with the others who have talked about ground problems, but here's an extra question:

    Is the computer plugged into anything else when it's being glitchy? Printer? LAN? Modem? It may be that there's a difference in ground potential between the computer and the peripheral that's causing a current flow between the two.

    If not, ignore the above but check the grounding anyway.

  • Is the phase thing a red herring? (Score:3, Interesting)

    by Grab ( 126025 ) on Tuesday January 17, 2006 @06:42PM (#14494813) Homepage
    (Or some other kind of scarlet swimmy thing...)

    Turning off and on at the same mains outlet will generally be "off, count 10 elephants/mississippis, on". Moving outlets usually involves physically moving the damn thing around, or unplugging a wire from one socket, taking the wire across the room and plugging it in somewhere else. Consider the time it takes to do this - could the power-off time be the significant factor, and the phase thing is a coincidence?

    Or on a similar theme, how about disconnecting the mains cable (and waiting some time) so that the mobos are fully powered down? That happens naturally when you disconnect the cable and plug it in somewhere else. Maybe try repeating the same action, but on the original phase.

    Not to doubt the fault-finding you've already done, but just adding a bit of devil's advocacy to suggest possible alternative situations with the same symptom.

    Grab.

  • Solution. Wired wrong (Score:2, Insightful)

    by jskline ( 301574 )
    Have an electrician come in and do some wiring checks and fixes. You have a combination of two problems causing you to see this.

    1: You have poor to non-existent grounds on one or more of the phases. This can be tested for by the electrician.

    2: The HOT and Neutrals are swapped around and generally this isn't an issue except that *modern* power supplies are getting cheaper and cheaper and this usually means cutting out *some* parts like full-wave bridges for half-wave diode sets, and similar tricks. This then

  • Might be due to current leakage or stray EMF (Score:3, Insightful)

    by GrpA ( 691294 ) on Tuesday January 17, 2006 @11:02PM (#14496442)
    I've experienced similar problems in the past, due to current leakage. Especially with different phases, but also commonly with poorly grounded devices or devices which had peripherals or cables running close to sources of high levels of common mode noise.

    Most commonly, when plugged into a peripheral or another device which is separately powered or grounded.

    What was happening was small amounts of current leaking in through peripheral components was affecting the power supply... Usually to stop them starting up. ie, hit the power button, no start, no lights. The leakage was in the micro-amps region, but was enough to leak back through the motherboards into the power supply, and cause a false fault condition reading on start up, and the PSU would shut down before it got started.

    The solution? In one instance, I decoupled the power rails. In another, better grounding. Another? Changed phase. The best solution was usually to find a better power supply that wasn't affected, but was not always possible.

    Often in these circumstances you can feel the current leakage, as it's often at high voltage but very low amps. Sometimes it feels like a slight tickle when you touch rivets on the case.

    Additionally, I've also encountered similar problems due to engineering faults, where a high impedance section of the circuit was acting like a radio antenna and was getting enough "reception" of a local signal (any strong electromagnetic radiation source) and causing a fault condition on power up that was not present during normal operations (when the applied signal was significantly stronger than the picked up signal).

    Solutions there include EMF shielding and redesigning the circuits.

    Problems like this are difficult to diagnose, as they are not always obvious, and there is very little you can do to test or troubleshoot directly. Often it involves experience and a little lucky guesswork.

    GrpA
  • solar flares.

    What I would do is go to my toolbox and get my $2 outlet tester and bring it to work the next day. If that turned up nothing, I'd go with an exorcist.
  • I'm reminded of the (apocryphal [snopes.com], but instructive) story of the car that starts or fails to start depending on the flavor of ice cream the driver chooses.

    You seem to have focused on the phase of the circuit the same way the driver in the story focused on the flavor of the ice cream. Try to think of your problem more in terms of the facts, and less in terms of your hasty conclusions.

    -Peter
  • I have had the same problem with my notebook. When I plug it in to certain plugs, it refuses to draw power from the AC, and beeps very loud very fast until I unplug it. If I plug it in to a different plug, it is fine, and then when I put it back in the "problem" plug it is fine again.

  • voltage between grounds at different outlets (Score:3, Insightful)

    by rcpitt ( 711863 ) on Wednesday January 18, 2006 @03:56PM (#14502917) Homepage Journal
    Many have posted posits about a problem with the ground and maybe bonding the neutral to ground. There are instances where even though the electrician has done his job correctly, there can still be a voltage difference between the grounds at various outlets to each other.

    There are two ways this can happen:

    • current flow in the neutral on circuits with more than one plug (many offices put 2 or 4 plugs on a single circuit) causes a voltage drop across the wire due to the resistance in the length of the cable. If the plugs are close together this is next to nothing, but if they are far apart (and many electricians spread them by hop-scotching the circuits around the room so two plugs close together are on separate circuits but the same circuit shows up 20' away again (and maybe 40' away again)
      Note that this can be induced in otherwise properly bonded circuits by the use of daisy-chained power strips/bars. It is the act of plugging in a (typically high-power) item on the end of the line (so the draw through the whole line is high) and connecting it via a signal cable (Ethernet, serial, USB, etc.) to something plugged closer to the junction box (electrically) that then ends up routing some of the ground current through the low-voltage signal line.
    • imbalance between the 3 legs of the 3-phase causing current flow in the common neutral which causes a voltage difference between neutral and building ground

    In general, the cure is to return to the bonded-circuit of yesterday designated by the orange plugs where they've been installed. These consist of a single plug per circuit (never more than one!) where ground is bonded to neutral at the connection box so there is no possibility that there may be a voltage drop due to current between individual recepticals.

    We seem to have gotten away from the specification and use of these (more expensive to install) power recepticals. I for one continue to specify them for most commercial installations and have yet to see any of the kinds of things mentioned here when they have been properly installed and used.

    The worst case I saw of this was in an office that was long and skinny in a brand new building (they were the top floor) with retail below. The office went in first, and the retail later proved to include a dry-cleaner that used quite a bit of power off two phases of the 3.

    A Unix computer in the center of the long office fed dumb terminals the length of both directions. The reception area was the farthest out - about 100' by wire - RS232 shield.

    The terminal at reception kept doing wierd things: hanging, mystery characters, and in fact died - 3 times! Lights on but nobody home!

    It turned out the serial interface was dieing - due to about 5 volts between ground and neutral which was pulling current through the cable's cladding and buring out the chip. The electrician poh-poh'd it saying "5 volts on a 120volt line was nothing to worry about" but in fact it was 5 volts on a 12 volt circuit and carried current in what should have been a voltage (high impedance) system. No wonder the interfaces were flaky and buring out.

    Replacing the power plugs with "home-run" single bonded ones fixed the problem.

  • Did you check the inserts with your monthly utility bill to see that the energy content includes at least the specified minimum level of Microsoft-branded electricity for your Trusted Computing hardware?

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