Hey guys, weird question for you. What kind of electrical issue would cause a projector to not be able to display at 60hz, and only at 70hz? There are 2 projectors ceiling mounted in 2 side by side rooms, they will only run at 70hz, but if you change outlets by running a cord directly to the 2 projectors they will run at 60hz. The only thing I can think of, and I may be completely wrong, is that the power cord in the ceiling is either defective, or running into interference...maybe...??

Opinions? :confused:

I know some other ghosts that like messing with living people's AV equipment. I'll check with them and get back to you. Maybe they'll know who's doing it and can get them to stop.

Hey guys, weird question for you. What kind of electrical issue would cause a projector to not be able to display at 60hz, and only at 70hz? There are 2 projectors ceiling mounted in 2 side by side rooms, they will only run at 70hz, but if you change outlets by running a cord directly to the 2 projectors they will run at 60hz. The only thing I can think of, and I may be completely wrong, is that the power cord in the ceiling is either defective, or running into interference...maybe...??

Opinions? :confused:DO you mean by change outlets that you are running a long extension cord from another location? What are you using for a signal source and how do you set it to 70Hz?

Sounds like a bad circuit and the other outlet is on a good circuit. What is the signal source plugged into?

They are using a different cord, coming from a second outlet in the room. This is the only thing they are changing in the setup, I'm not entirely sure it could be from the source. A bad circuit on the first outlet they tried sounds right, however they have advised me that it has been "tested, monitored, and deemed good"

They are using a different cord, coming from a second outlet in the room. This is the only thing they are changing in the setup, I'm not entirely sure it could be from the source. A bad circuit on the first outlet they tried sounds right, however they have advised me that it has been "tested, monitored, and deemed good"

They? Who are they?

THEY need to provide you with some numbers for the outlet that has the problem and numbers from the outlet that works fine. Volts, amps, polarity, and range of voltage. Most circuits in homes do not run a consistent 120v but fluctuate up and down. What range do THEY consider normal? Did they validate the ground?


Your write-up is somewhat confusing to me still. There's a lot of missing info. Are you using a HTPC? How do you know you are sending 70hz vs 60 hz?

I'd like to help but I need a lot more info on your setup.

What is your signal source? Where does it plugin?

I agree I need more info, unfortunately they are not forthcoming with this. More than likely they are using a video codec outputing at a set range. Could changing the power outlet affect the signal coming in, or is it affecting the actual projector? Could they have the hot and ground backwards on the outlet?

I would say just off the cuff, something else plugged into the circuit in question is causing the problem. Need to look at everything plugged into the circuit that checks out when there is no draw on it. Could be a loose wire, a short, or a bad power supply that when connected to the circuit causes the problem.

Thanks again recon

Are you talking about residential rooms or industrial halls? Industrial eletcrical systems might have some frequency converters for other reasons (like energy savings, speed regulations of ac motors, etc.) and projectors should not be connected to those outlets. Are there any inverter type un-interrupted power supplies (UPS) in the path? If so, imperfect conversions from AC to DC and then back to AC may inadvertently change the frequency.

Not residential. They have a massive overall system, not sure what is on this same circuit without being on-site

Zack S, you are being very mysterious with this whole "they" thing.

Who are "they"? What kind of environment are you trying to install these projectors into? What projectors are being installed?

Without more info, as others have suggested: something else is plugged into that circuit causing bizarre behavior, or the circuit itself is not properly configured.

shinksma

There is nothing mysterious, just not wanting to throw down names on a public forum. The two rooms are two large auditoriums, each outlet appears to be on the same circuit as these are the only two having issues.

Well, the reason I'd like more details about the client (even just "school" or "car factory" or "Irish pub"), is because industrial sites tend to have lots of "industrial" power configurations (208VAC single phase, double phase, 240VAC triple phase, 120VAC 400Hz for aviation, etc).

On the other hand, schools might have had a circuit installed for one use, then re-configured for another over time, and Something Has Gone Wrong. Whereas an Irish pub should really only have typical residential type power available (120 VAC single phase and 240VAC two-phase, both at 60Hz). And something with lots of UPSs plugged in for PC equipment can really wreak havoc when the UPSs start to fade.

I would have those circuits re-tested with an oscilloscope or freq meter, not just a voltmeter, to make sure that "they" really have configured the power correctly. And look for a DC bias that might be fouling things up.

Also, defining the video source and how it gets set to 60Hz vs 70Hz would help a lot in diagnosing the issue.

Hope this help, IMHO, AFAIK, etc,

shinksma

They are an education customer, we didn't do the original install, at least I doubt we did, and they are now having problems with the current configuration. My main question was more along the lines of, can a bad power cable/interference cause a projector from not displaying 60hz. The signal is set, 1280x768 @ 60/70hz, 1400x1050 @ 60/70hz etc, etc. Everything pumped into the codec is output the same, again, I doubt it's the source.

...My main question was more along the lines of, can a bad power cable/interference cause a projector from not displaying 60hz....


Since the projector shows 60Hz at another outlet, most likely it's not the projector. Bad cables should not change frequency. For interference to change the frequency, it has to coherently add to the mains signal (60Hz) on a consistent basis. This seems highly unlikely to me. My suspicion is, somewhere along the same circuit in the "faulty" rooms, there's diac/triac or inverter based device, faulty UPS or frequency changer for speed control that is creating this change in frequency in that particular circuit. Not sure if that's what you mean by "interference." These are all speculations; until proper troubleshooting is done with appropriate measurement tools, difficult to conclude anything. Sorry, not of much help.

I agree on it not being the projector, obviously it can display 60hz. Cabling should not change the frequency, correct, but can it? As far as the interference, say you have the power cable running over 40+ fluorescent light fixtures, could that cause a change in frequency? I'm just trying to narrow it down, I am pretty sure it's an existing problem with the power infrastructure, or supporting components, but want to rule out possibilities if at all possible. I honestly appreciate all the help, I'm not too knowledgable on electrical issues.

Be careful here. The outlet may be miswired. Have an electrician verify the wiring. There could be substantial current on the ground which is upsetting the projector electronics. Avoid getting your body between the projector and cable connectors - like touching the projector metal chassis while plugging in cables.

There is a way to test this with a cheap hardware store part. But I won't post it because in the wrong hands it could be deadly with a miswired outlet. Anybody else wants to accept the liability - go ahead and post it!

I agree on it not being the projector, obviously it can display 60hz. Cabling should not change the frequency, correct, but can it? As far as the interference, say you have the power cable running over 40+ fluorescent light fixtures, could that cause a change in frequency? I'm just trying to narrow it down, I am pretty sure it's an existing problem with the power infrastructure, or supporting components, but want to rule out possibilities if at all possible. I honestly appreciate all the help, I'm not too knowledgable on electrical issues.

You have to test every device / equipment on the circuit. I would run an isolated circuit with it's own breaker for your AV installation. If you have all kinds of other devices like 40 FL fixtures on it, you are asking for trouble.

I'm not actually doing the install, just helping them diag the problem. I would hope they don't have the fixtures on the same circuit, it was more of a hypothetical question.

This sounds like a issue to do with a earth loop problem it may interfere with signal or projector circuiting.

What I'm thinking is, that the power to your source (AV gear) is coming from a different location and on a different circuit to the projector.

The cabling rule is you must have your source and display on the same circuit and cabled from a central point.

There is a way to test this with a cheap hardware store part. But I won't post it because in the wrong hands it could be deadly with a miswired outlet. Anybody else wants to accept the liability - go ahead and post it!Totally piqued my interested. Can anyone elaborate?

Thanks guys

There is a way to test this with a cheap hardware store part. But I won't post it because in the wrong hands it could be deadly with a miswired outlet. Anybody else wants to accept the liability - go ahead and post it!

Glimmie, I would like to know what you're speaking of as well

Reading only the last two posts, I would as he is telling te tst is to use a cheater plug to defeat the ground pin on a three pin plug. If one uses multple three wire plugs in a system and these plugs are plugged in different outlets, one will induce a ground loop audible as a 60 cycle hum through the speakers. The test is to cheat these plugs bu using a cheater plug which lifts the ground pin. ou never want to have more than one three wire ground. Of course this would be a safety issues but it normally OK to test this way. Just don't touch equipment chassis during the test a;though this is highly unlikerly but possible to put your body as a ground path if you do. The fix is to isolater your components with expensive coupling transformers.