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Flickering Monitors?
Anonymous Coward writes "Our SB Office runs a small 2 Server network with 4 workstations in the LAN, each connected to a dedicated APC Surge protector. The building has a backup power generator thus we didn't see the need for a UPS. For some odd reason all our monitors flicker a lot. We've tried everything from changing resolutions/refresh rates/video cards/monitors and spacing the monitors farther apart from each other - all to no avail. Could this be a building power supply problem? Some have suggested there may be some magnetic interference but visually inspecting the surroundings doesn't leave us with a culprit for the cause. Could this be fixed by the simple addition of a good UPS? Any help, tip or information would be gladly appreciated. Thank you."
I had this problem when I placed a table fan next to my monitor on my desk in the middle of summer. The spinning magnets cause a very annoying flicker, and maybe hopefully not do some damage. Try moving the monitors farther away from racks or the generator, and that might fix the problem.
Yawn.
A coworker of mine who is very sensitive to screen flicker had a similar problem--every monitor he tried would cause headaches. They gave him a flat screen and that solved the problem. That was at about the time when we figured out that on the other side of the wall from his cube was a wiring closet, so it was the electrical fields from the wiring closet messing up his monitor.
If you can find the source of the problem, you might be able to shield it.
How close is the backup power generator to your room? I think this could be the problem - due to EM inteference. A similar problem occurs if you have e.g. a large bass-box and you place the monitor next to it, which I hope you are no doing!
In fact, I have experienced exactly this where I work. There is a fscking great big generator right next door to me. My original monitor flickered like hell when I moved in to my new office. No matter what I did - where i put the monitor, whatever the settings, the flickering was completely unbearable.
The only way round the problem I have found is using a flat-screen. LCD doesnt suffer the same EM inteference problems as cathode ray. Hence no flickering.
Luckily I was able to find someone kind enough to swap monitors with, saving me some expense (my old CRT monitor was pretty darn huge and cool, though). Other than forking out for some new flat screen monitors, I dont know what to suggest!
But if you're going to lay out that kind of cash, replacing the monitors with cheap analog LCDs will make them immune to most kinds of interference and cut your power consumption significantly. Replacing them with digital LCDs (DVI-D) will make them work properly in the middle of a pile of supercharged magnets.
That said, I'd find someone who's comfortable throwing a scope on the line and checking out your power situation. If your building's UPS is throwing out an imperfect signal, it may be slowly killing your machines if left unrepaired. PCs don't take well to current variation or screwy spiked or squared voltage waveforms.
I would check for power problems. I once had a similar situation, where you could actually hear something when the monitor screens would shrink a bit. One quiet night I figured out that it was the power hungry Sun SparcPrinter on the same power circuit that was firing up the fuser periodically. It was causing brown-outs.
m
If all of your flickering monitors are on the same circuit, or worse, the same surge protector, try changing that.
I have had surge protectors that were "used up" and were spiking the power on their own. Try taking the surge protectors out.
You might try monitoring the power voltage with a mulitmeter to see if you see a change when the flicker happens.
Try testing with a small online UPS for one monitor to see if that cures the problem. Note that it cannot be a standby UPS. Those won't cure brown outs. http://www.pcguide.com/ref/power/ext/ups/types.ht
Ever dream you could fly? Get up from the Flight Sim. I Fly
I have this exact same problem. I've given up and resorted to using 60hz refresh only. I checked for lights, moters, dirty power, everything. Remember, this isn't really flickering, this is a kind of shaking. Your eyes will filter it out if you're using a black background, but it's unbearable if you're trying to do anything other than watch a dark movie from accross the room. (I have a 19" sony trinitron in my living room)
Oh, and ALL my monitors do it, 14", 17", 19", cheap to midline to pricey. They also do it in ANY room.
I really wish I knew what caused it... I'm ready to move soon though, so hopefully things will be better then.
--Mike--
All of the office equipment will be 2-phase. Three-phase wiring is mostly used in industrial settings, although it might also be used with consumer oven and electric clothes dryers.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
I'll bet it is magnetic interference. One of my old offices was near a generator, and the monitor would go crazy all the time.
;)
My friend's got this device that you use to amplify a telephone. You can also use it to listen to EM radiation -- put it near your monitor or electrical wires and hear a nice hum. If you get one of those (I'm sure they're pretty cheap) and hear a hum in the middle of your office with your equipment off, then you'll know you've got a problem.
Something like This. It might be cheaper to begin with and it's not another component to go bad :)
There are other similar products, but that should give you a good start.
I have developed a set of debugging techniques over the years that seems to work in most every situation. It's a matter of looking at a problem from the proper level of abstraction and using the tools I already know how to use:
How do you find a needle in a haystack?
With all seriousness, pick up a good compass at a sporting goods store and do a survey of your office. Walk around the room and see if there are any deflections. Whether it's an electric current (which induces a magnet field) or an actual magnet in near proximity to the magnet,
a good compass should point you in the right direction (pun intended!)
Things I have experienced in the past which affected my monitors, in no particular order:
One other thing to try is to bring the PC, monitor, and all peripherals home and see if the problem exists there, too. If so, then it's likely there's something flakey about your equipment. If they are okay, then it would indicate there's some environmental factors at your office.
Good luck! And please fill us in on what you find!
- Funky power is going to shorten the life of your hardware significantly. I used to work at a company where a series of IS servers "mysteriously" kept failing. When it became my turn to rebuild the fool thing I discovered it wasn't in our many-million-dollar server facility but down the hall from it, under a counter, plugged in next to a photocopier, big old laser printer and two fax machines. After discovering this and taking a look at the transients I'm was impressed they were lasting as long as they did. In your case hiding the problem with LCD displays isn't going to solve it.
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On the other hand it could be lighting. Tube lighting flickers a lot and that can interact with the refresh rates on your monitors, particularly if you've all the same brand of monitors or your OS or staff keep setting them to the same refresh rates. Test this by adjusting the refresh rates of some monitors via software. Make one 65Hz, another 75Hz, if you can make another 85Hz. Also try working without the tube lighting. Get in some fill (torchier) and task (desklamp) lighting, preferably incandescent, and see if they obviate the problem.
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So, if its not your eyes what devices are within 10m (same floor, floors above & below)? What devices are on the same circuits as your server? Are any of them motors, generators, heavy or intermittent draw devices? This includes laser printers, big fax machines, refrigerators, microwave ovens, etc. Survey all of this, ask your neighbors, ask to take a little tour for yourself, talk to the facilities folks.
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Put servers on separate UPS's with power-line conditioning. It'll provide a backup to that generator (they know when to fail), clean up your supply, provide a bridge between the mains failing and the generator kicking in, just make everything a while lot more stable for your more expensive and critical hardware. Have purchasing get you a separate UPS/conditioner for each server and for heavens sake don't plug the monitors into them. If you really need server monitors when the power goes out get small flat-panel ones and plug them into their own UPSes (will give you handy spares you can sacrifice at need.) BTW these UPSes need not be power-all-day mondo models, just enough so that if that generator doesn't come on or there is some other problem they'll give everything time to shut down properly.
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Replace the UPSes, "surge protectors" and the like every year or two. After enough hits the cheapie surge protectors become unresponsive and are essentially extension cords. The batteries on a UPS also age and start to loose charge faster. When you replace them migrate them down the critical path if you want but for heavens sake spray paint them, permanent marker them, something so they don't end up plugged into something really critical again.
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Call an electrician. Seriously. 5 minutes with the hardware hanging from their belt and you'll have the comfort of knowing something. Also buy a compass, about US$15 or US$20 for a decent orienteering one. Walk it around the room to see if it shows any bobbles, it might help you track down the problem, or at least determine if the effect is strictly optical, electrical or there is a magnetic component too.
So between the time, services and hardware we're talking a few hundred bucks. Is that overkill? No way. That's popcorn compared to the disruption if one of your critical devices fails catastrophically, also nobody wants to work in a flickery environment. You wouldn't put up with a random "Feep" noise, why expect folks to deal with the visual equivalent? Staring at displays all day is tough enough without letting them degenerate into flickery ones.Oh, and if nothing else works, remember the order of propitiation: Chicken, Goat, Virgin. If you ending up needing the last one call Corp HQ's IS, we usually have one or two on staff we could spare (we keep them just for this purpose.)
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
That's not off topic.
Chewing can cause CRTs to appear to flicker, especially form a distance.
I'd check any florescent lights. Turn them off, and see if the flicker changes.
and it was due to proximity to the big APC ups's and their tranformers (or whatever was generating such a strong magnetic field).
my solution: convert to lcd displays. I am now using a pair of 'old' SGI 1600sw displays and obviously all my flickering is gone. before I used a pair of dell/sony 20" monitors and the shaking (not really flickering) just drove my eyes nuts.
--
"It is now safe to switch off your computer."
One of my clients (a large law firm) had a user who seemed to be death to monitors. They tried new monitors. They tried new video cards. They tried a new computer. They even tried moving her to a different office. Monitors still died.
One day, they called me and said "the monitor flickers." I went over there, asked some questions, and found out that the monitor has ALWAYS flickered, but it just now started to drive her nuts.
So I turned off the typewriter that was next to the monitor (which stopped the flicker) and told them that the typewriter (which was always turned on and always next to the monitor) was the likely perpetrator of death, and physically separating them was the only solution.
Another client, a large print house and manufacturing facility, has a few which flicker whenever a machine starts up.
In your case, unlikely it's the backup generator, because it's not running all the time.
If the problem is indeed in the power, you'll need to get a power filter. What that does is takes dirty power and gives you a nice, smooth, clean 60Hz (or 50Hz in Europe) sine wave.
Give me my freedom, and I'll take care of my own security, thank you.
Does the flickering go away when you stop eating crunchy foods? If so, then I've got an idea what might be causing this...
It's only software!
I've found on more than one occassion the ole' HPLJII's (and a few variants) have a horrific draw on the power grid every few minutes.
That horrific draw wouldn't be right about the same time they actually print something, would it? Laser printer (especially older ones or bigger ones) draw a ton of power while charging up their drums.
No, it is not two phase. It's single phase. Bear with me and I'll explain:
The power company transformer has a secondary winding with a grounded center tap. The voltage between the two poles of the transformer is 240V; the voltage between one pole ant the center tap (ground) is 120V. The grounded "neutral" wire is connected to this center tap.
If you hook up a scope between pole "A" and neutral, then hook it up to pole "B" and neutral, (providing the neutral is connected to the same pole of the scope) you will find that one is the INVERSE of the other, or reverse polarity. They are not 180 degrees out of phase, because YOU have reversed the polarity in hooking it up. Connect the scope between the two poles, and you will find a 60Hz sine wave of twice the amplitude (240V) as between one pole and neutral. There is no point to 180-degree 2-phase, because summed with cross polarity you get 0V and summed with same polarity you get single phase twice amplitude.
If there was a two-phase situation, you would see a sine wave that is the sum of two sine waves, offset by 120 degrees from each other. No point to this, because the resulting waveform is ugly and inefficient.
Three phase power is used primarily for electric motors. For a given power rating, a 3-ph motor can be made smaller and cheaper, runs cooler and more efficiently, and has greater starting torque than a 1-ph motor. Besides, a 3-ph motor can be reversed easily.
Occasionally in a commercial or industrial setting, you will find lighting which is "208" or "277" volts (odd numbers, hey?). This is because they are running from different legs of a 3-ph transformer bank than your ordinary stuff.
Back to the 1-ph system... it's not truly a neutral wire unless the loads on both poles of the transformer are equal. In a 120V circuit, it is NEVER a neutral wire because it is carrying current back to the power source.
In spite of the fact that the "neutral" wire (properly termed, "grounded current-carrying conductor") carries current, the potential between it and ground should always be zero. Anything else indicates a very serious and hazardous problem. If this center-tap wire fails between the transformer and your electrical panel, you may get a situation where the voltage between pole A and ground is greater than pole B and ground (depending on load), summing to 240V. This is a very dangerous situation (kills every appliance and computer and in the event of a ground lift energizes the metal frames of everything) and if you have it, turn off ALL POWER NOW and call either an electrician or the power company immediately.
Give me my freedom, and I'll take care of my own security, thank you.
The building has a backup power generator thus we didn't see the need for a UPS.
Anyone else find that funny?
One thing you may be able to try is powering down EVERYTHING in the building... and I mean everything: water heater, coffee pot, alarm panel, wall clock in addition to the usual lights & computers. Unplug other computers, monitors, small appliances, and TVs. Turn large appliances off at the electrical panel; some have transformers and electronics that remain energized when you hit the power button. Remove battery powered devices like cell phones and PDAs from the building. Well, maybe you'll need a flashlight, but it will be pretty easy to tell if that's the culprit.
Leave the computer and monitor in question on, though. Does it flicker? If so, problem is external to the building. No? Start turning things on one by one, checking the monitor every time. If it's one thing that's doing it, this should isolate the problem.
Give me my freedom, and I'll take care of my own security, thank you.
The gen set is great, but what about the lag time between power failure and generator startup?
You need something to carry you through. A UPS is great for this. (Now if you have a whole-building UPS for this purpose, that's great.)
What if the gen set fails?
Give me my freedom, and I'll take care of my own security, thank you.
A friend of mine has the same problem, and he also has 'light rail' (Metra tracks) about fifty feet away.
The 'screen shake' is a constant problem, there is also wide-spectrum 2.4Ghz interference at regular intervals, coincident with the passing of passenger trains.
I do not deploy Linux. Ever.
Just so you know, two things you said contradict each other:
In a 120V circuit, it is NEVER a neutral wire because it is carrying current back to the power source.
In spite of the fact that the "neutral" wire...carries current, the potential between it and ground should always be zero.
If its carrying current then there will be a potential between ground and neutral, which is the real world case. BTW, neutral and ground are bonded together, once and only once, usually at your circuit box. The neutral is very close to zero, but never zero for loaded circuits. Secondly, an ideal 3 phase motor would not return any current on the neutral, but they don't exist, so in three phase, there is current on the neutral, granted very small, but still there.
A side note: In a three phase system, neutral lines used to be sized to the same gauge as one of the phases, but things like computer switching power supplies, produce harmonics on the line which would add together on the return from the three phases and burn out the neutral, so now they are sized larger.
"Karma can only be portioned out by the cosmos." -Homer Simpson
Some evening after work, pack up your computer and monitor and bring it off site. See if it still flickers in a completely different environment. Either you have some electrical noise or you bought cheap monitors.
There is no reasonable defense against an idiot with an agenda
:wq
Be aware that most cheap UPSes (Uninterruptable Power Supplies) are actually SPSes (Standby Power Supplies) and only provide basic spike/noise filtering when normal AC voltage is present.
A true UPS (such as the 1KVA Siemens that sits under my desk) converts the AC voltage to DC then runs it through an inverter to create a rock-steady and smooth AC output. It doesn't matter what comes in on the mains side (short of a direct lightning hit), the output side is clean as a whistle.
If you want to get rid of low-frequency voltage/phase fluctuations on your mains supply then you really have to use a true UPS or at least a big, heavy, ferromagnetic resonator.
With all this discussion on using a UPS to reduce line noise it's worth pointing out that most of the low-cost UPSes on the market are actually SPSes (Standby Power Supplies).
Until such time as the mains voltage drops below or above the trigger level, they're nothing more than a medocre spike supressor and filter -- just like the low-cost spike supressors you can buy inside power-boards.
A true UPS runs a full-time inverter.
Incoming mains power is rectified, smoothed (turned into steady DC) and then fed into an inverter that creates the AC waveform which is used to power your computers etc.
Short of a lightning strike, nothing that happens on the input side will affect the output waveform.
Spikes, voltage and phase fluctuations are all eliminated when the AC is converted to DC inside the box.
By comparison, the cheap SPSes (erroneously refered to as UPSes) simply pass the mains voltage through a crude filter and spike suppressor unless they're triggered into inverter mode.
Another problem with these cheap SPSes is that they often don't play nicely with low-cost generators.
I used to have a 600VA SPS that I used on my PC but found that the power outages I was getting were often an hour or more in duration (I live in the countryside where trees regularly fall across the lines).
To solve this problem I bought a 2KW Honda generator but found that when I plugged the SPS into the generator it would repeatedly kick in and out every 2 seconds or so. Turns out that most SPSes are very sensitive to the frequency of the mains and most small generators tend to have a frequency variation well outside the SPSes acceptable limits.
Some better SPSes (such as the APC line) have an adustment so that the sensitivity to frequency fluctionats can be reduced but sometimes even this isn't enough if you're running other loads of the generator.
That's why I bought a true UPS. You can feed it anything and it just keeps putting out a nice smooth, superbly regulated AC waveform. By going up to 1KVA I also obtained an extra 15 minutes of operation on batteries so I don't have to rush to get the generator out and started.
Check the cables. (really!)