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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."
stop eating those potato chips there.
Do not go gentle into that good night. Rage, rage against the dying of the light.
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!
I lived in a place for a while where if the monitor was set to anything above 60Hz the screen image would waver back and forth quickly. We tried everything we could. The house was old so we ran some new electrical wire. The breaker box was new and properly grounded as well. There were no visible major power lines around the place. Some of those high power lines can cause interference. I don' think there was a cell tower nearby either. The only thing I can think of was that there were railroad tracks running behind the place. Its possible that the railroad were sending radio communications and interfering that way. At the time I lived there I didn't have a UPS but my brother whose house it is has one now and it doesn't seem to help.
In Republican America phones tap you.
My desklamp is a neon, and it's just above my monitor. Whenever I light it, even if I'm at 800x600@100Hz, it will flicker. So I never use it (prefer ambient light).
I also whitnessed some speakers doing some weird things to monitors. Another thing to check for.
I'm experiencing a related problem when somebody turns off the light (a fluorescent tube - hope that's the correct term, the dictionary says so ;-) in another room, the monitor flickers for the portion of a second. I guess this is caused by a voltage spike that appears when the light is turned off.
Regards, Specialist2k
Any of your questions could be the culprit, and if that is the case, a separate UPS for the monitors would likely fix the problem.
But you don't say what type of monitors these are, or their age. Which brings us to the question: ARe these just crappy, cheap monitors?
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 had problems at a lan party that was finally traced to my monitor cable running too close to several power cables.
Degaussing scares the bad magnetism out of the monitor and fills it with good karma.
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've got the same problem in my basement, but I've also realized that 2 things are causing this issue:
1. Bad Ground/Non-existant ground. Take a good APC surge protector (mine has a little red "ground fault" light on it) and test the outlets/curcuit that the monitors are plugged into. If that light lights up, what could be happening is that you're getting a power drain through ground (or no ground at all) and the voltage on the "neutral" side can be varying.
2. Overloaded phase on 2 phase ??? (House Wiring) -- A friend of mine explained to me that since there are 2 phases in house wiring (may not apply to your SB office) if you overload one side, you could cause fluctuations in +V on the other phase. I tend to believe this theory (in conjunction with my other problem) causes flicker on my monitors; when the furnace + washer kick on, the flickering gets worse.
That's my personal experience -- hopefully it helps.
Karnal
--Mike--
What ever happened to experimentation, isnt' this part of the scientific method? :)
Power corrupts. PowerPoint corrupts absolutely. E. Tufte
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.
First of my guess would have been proximity, but you stated that you'd tried moving them appart. What happens when only one is plugged in? Do you still see the effect?
Odd as this may seem, 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. Something to do with keeping the internals to the right temp or somesuch. Anyway, yank the power cords of any printers you have in the nearby vacinity.
You'd be surprised...
You've got an office with 4 computers and lan. But instead of borrowing a UPS for a time or testing a monitor out of the office you just ask slashdot: could this be a power supply problem? Probably could and probably could not. Probably it's just visual interference with lamps, or a software problem (various versions of Windows tend to be very weird about monitor specs).
Even the producer of monitors is unknown. I doubt power supply will cause bad image on a new digital NEC and probably the best UPS would not help 15 years old samtron or like. You have much better chances to locate the problem where you are than we here.
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."
Place each monitor in an appropriately sized six-sided grounded metal box with a small hole just big enough for the power and video cables.
This should elimiate your magnetic interference problems. I would also recommend the chrome option for a really classy look.
Healthcare article at Kuro5hin
In one of the buildings that I worked in, my monitor kept flickering no matter what I did. Regular monitors (Apple, SGI, Sun, Sony) were all but unusable. The only monitors that came close to being usable were old IBM Trinitron monitors that were bought with old IBM RS6000 320's and 340's. These monitors weighted 100 lbs or so and probably had significant sheilding. Additionally, it may have been the BNC cabling. We tried UPS's and other power conditioning to no avail. We tried bringing in power from other rooms, no luck.
At any rate, after much eye pain and quite a few hours of tracking the problem down, it was found that one of the main power lines for the building was in contact with the metal frame of the building near that office. I guess that it was producing a 60Hz oscillating electric field and that was messing up the monitors. At any rate, when that power line was fixed, the monitor flickering went away.
that is is EM radiation.
Want to know how to check?
See if your balls are shrunken!
Maybe your lights are flickering, but your monitor is rock solid?
First of all, you almost certainly need to invest in either a voltage regulator or a UPS (which will perform the same function) to clean up the power going into your monitor/machines.
Secondly, check the proximity of items that are very high voltage and contain magnets. Something missed by a lot of people that can cause this problem is the proximity of your speakers/subwoofer to your monitor. I have a 21 inch ViewSonic monitor and a set of Klipsch ProMedia 4.1 speakers and they don't like each other very much when they get too close together.
Cheers,
Blake
Blake
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.
I think maybe your eyes are what's flickering. This happens to me from time to time.
Do you get dizzy spells? Have you ever fainted? Do you get motion sick?
With practice, you should be able to shake your head at the right frequency, thereby eliminating the flicker on your monitor. One drawback of this approach is that everything else in the world quivers and people think you have Parkinson's disease.
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.
Maybe the guy just has an ElectroMagnetic Personality.
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.
Look for Two-way radio's and Cell Phones, or another client in the building with radio equipment. I get speaker pops and monitor shake when some cell phones are used near my monitor and speakers. We used to be able to reboot older Compaq laptops by just keying up a two-way Motorola radio. If my buddy on the other side of the cube pissed me off I would just hold the radio to the side of the cube wall and key up. His laptop would just spontaneously reboot itself.
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
Actually, they charge the drums periodically even when you're not printing--and that was what was causing it.
We had the same problem in our company in the past. Our offices where underneath high-voltage power lines coming from a power plant. The EM radiation coming from these lines causes flickering. We had to replace all our CRT's with TFT's to solve the problem
A plugged in electric clock caused the monitor to flicker. When I moved it away that stopped it.
That we finally determined was being caused by some regular electrical wiring in the wall directly next to the monitor! Moved the monitor to the other side of the desk away from the wall- problem fixed. In any event, its definitely interference from somewhere- just finding out where can be a bit of a headache.
You still need a UPS. A backup generator can't start up fast enough to keep your systems running in the event of a sudden blackout or brownout. An active UPS produces incredibly clean power and eliminates even the slightest hiccup if your generator needs to start up.
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.
Yeah believe it the tubelights in the room doesnt remain constant but flicker. Changing to a halogen bulb really worked for my computers here. Try this first: On a good afternoon turn off all tubelights and turn on all monitors. Open the curtains to let sunlight in and check the flicker.
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
Dint't see anyone mentioning this, but aren't your desks by any chance fancy ones with motorized control? You have a control that makes them higher or lower, among other things? I've had that problem in my company, where engineers loved those desks more than mom, and monitors would simply flicker from being near the engine under the table. I told them to fix the tables to their preference and then unplug the engine from the power socket.
/Pedro
most of the comments on this discussion have delt with em interference of some kind. i bet that this is indeed the case, if you can't get rid of the interference, you can block it quite easily. one thing we do with sensitive scientific equipment is to put it in a faraday cage. this is just simply a metal wire cage. em interference cannot penetrate a conductor (as long at the spacing between the wires is smaller than the wavelength of the interference - the interference you're getting is probably on the order of 1 meter or longer, so you have nothing to worry about). you should be able to get away with a cage the covers the back and sides of the monitor - it would be kinda useless to cover the front :). if you know where the interference is coming from (i.e.wires in the wall), you can just block the source (put a mesh between the wall and your monitor). hope this helps.
Check the cables. (really!)
Like the first person, I had a problem with keeping a fan next to my computer over the summer. Run a quick scan of the area, check for any systems that involve a couple of magnets rotating quickly (an air conditioner or some sort of system like that may do the same thing)...
Goodluck.
Mike