Flickering Monitors? 66
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."
Re:You might want to... (Score:2)
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.
Fans? (Score:3, Informative)
electrical fields (Score:4, Insightful)
If you can find the source of the problem, you might be able to shield it.
backup power generator (Score:3, Informative)
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!
Magnetic interference (Score:1)
Re:Magnetic interference (Score:2)
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.
Railroads cause VGA interference? (Score:2)
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.
Watch for close neons... (Score:1)
I also whitnessed some speakers doing some weird things to monitors. Another thing to check for.
Re:Watch for close neons... (Score:1)
Voltage Spikes (Score:1)
Regards, Specialist2k
Your not going to like this. (Score:1, Interesting)
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?
UPS will help if it's not magnetic (Score:4, Informative)
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.
Re:UPS will help if it's not magnetic (Score:2)
My monitor is "wavy" (I've tried 3 different ones), and I had one die. My DVD player is flaky (crashes regularly, locks up, etc), and I have a PC that just dies once every couple weeks for no reason.
I'm afraid for my current hardware. My DVD player is permanently damaged (it's at my Girlfriend's place now, and still locks up...), and one of my monitors just snaps and dies all the time (hard power interruption fixes it temporarily. I wonder if I can hold my landlord responsible for damages?
Do you have more details on what bad power can do to electronics? (quared/spiked/etc?)
I'm moving in July (on Moving Day, here in Quebec), but in the mean time, I just can't afford to replace my gear.
S
Re:UPS will help if it's not magnetic (Score:1)
Re:UPS will help if it's not magnetic (Score:2)
I think the power in my apartment is like this.
My monitor is "wavy" (I've tried 3 different ones),
OK, I confess. I live in the apartment next door to you and I've been running a 20kV Van de Graff generator alongside the superconducting magnet that I keep "Frank" in.
[All kidding aside, my boss at the consumer electronics store told me to do this for a few weeks to drum up some business for new TV's, computer monitors from my neighborhood.]
Re:UPS will help if it's not magnetic (Score:2)
No specifics, but I'd wager a question posted to sci.electronics.repair would net you more replies than you can count.
Check those cables. (Score:1)
Good be power (Score:2, Informative)
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
I have the same problem.... (Score:1)
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.
2-phase (Score:2)
Re:2-phase? NOT! ...and safety (Score:3, Interesting)
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.
Re:2-phase? NOT! ...and safety (Score:2)
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.
Backup power takes time (Score:2)
--Mike--
Buy and Try (Score:1)
What ever happened to experimentation, isnt' this part of the scientific method? :)
Re:Buy and Try (Score:2)
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.
Probably EM, how to measure.. (Score:2)
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.
You might try... (Score:2, Informative)
There are other similar products, but that should give you a good start.
Looking with the right tool (Score:4, Interesting)
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!
rule number 1. Re:Looking with the right tool (Score:2)
Step by step (Score:5, Informative)
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.)
Re:Step by step (Score:2)
Re:Step by step (Score:2, Interesting)
They had an older style table saw, the type that rarely has a blade guard (nor can you use them anyways when ripping an 8' piece of ply). He powered it up once, it ran normally. He turned it on or off a couple more times, and finally said "Got it". Though I could distictly here that the saw was on, the blade appeared not to be spinning. When he slid a two by four into the blade it slowedthe rotation down just enough that you actually could see the blades turning, though it was in a funny oscillatiion, like dancing in a high speed strobe light. Turns out, the flourescent lights flickered at just the right frequency to make the moving blade appear to be standing still.
How many HP LaserJet II's do you still have around (Score:1)
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...
Re:How many HP LaserJet II's do you still have aro (Score:2)
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.
Re:How many HP LaserJet II's do you still have aro (Score:1)
I had the same problem (Score:2)
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's just this simple (Score:1)
This should elimiate your magnetic interference problems. I would also recommend the chrome option for a really classy look.
Sometimes it's your building. (Score:1)
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.
my guess is (Score:1)
Want to know how to check?
See if your balls are shrunken!
Re:my guess is (Score:1)
So THATS the reason, all this time I thought it was genetics!
Some other possibilities (Score:1)
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
Just read the comment, I can't think of a subject (Score:2)
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.
snack time! (Score:2)
Oh geaz (Score:2)
Anyone else find that funny?
Finding the source (Score:2)
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.
Re:Finding the source (Score:2)
Do this first: Turn them all the way down/off and see if your problem goes away. Cheap SCR dimmers are *the biggest problem* in causing noise in audio systems, that's why you never find them in radio stations, auditoriums, or recording studios (they've got mucho-buck lighting control systems that don't put out dirty-waveform EMFs).
You still need a UPS (Score:2)
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?
Re:You still need a UPS (Score:2)
All too often I have seen what was a small server room expand with hardware upgrades and with no forsight to include upgrading the wiring. That poor 20 amp breaker eventually will be a rude awakening to those who didn't want to include the time of an electrician into their plans.
I feel a local UPS in addition to the other larger backup power generation is a great idea. They are small, easily servicable and replaceable by just about anyone; whereas a failure of a large UPS may require a service call.
I once had the pleasure of being close to a large 1.6MW Cat twin turbo diesel generator when it decided to toss a valve out of the cover. A few hundred hours of operation into another shift, the shaft between the engine and the generator snapped. Nothing like 2800 horsepower wanting to be free once in a while... After several years, the nicad battery pack failed to turn over the two starter motors. They were replaced by a pack of lead acid batteries (cheaper, but an expected life 3 years.)
While the large sets are lifesavers, they can have extended downtime due to their size. They seem to work well in addition with small, replaceable UPS units.
Two-way radio's and Cell Phones (Score:1)
Go off site (Score:3, Insightful)
flicker.... (Score:1)
Had a similar problem (Score:1)
backup generator still needs a UPS (Score:1)
UPS versus SPS (Score:2)
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.
Motorized desk? (Score:1)
/Pedro
EM Interference (Score:1)