Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×
Apple Businesses

Fluorescent Lights Magically Activates iMac? 108

Posted by Cliff from the weird-goings-on-here dept.
bats asks: "In my computer room at home, I have several machines -- and a fluorescent desk lamp. Among my various boxen is an iMac DV (slot loading) circa 1999. Its configured to go into power saving mode, but respond to wake-on-lan packets. The weird thing is this: If I flip on the fluorescent desk lamp, the sleeping iMac will suddenly wake up! This happens with 100% consistency. The desk lamp is plugged into a power strip and into the wall. The iMac is plugged into a UPS and then into the wall. The network switch for the room is near the desk lamp (1-2 feet) but the iMac is some distance away (8-10 feet). My question is: WTF?! How the heck does the iMac know when the light comes on? It seems like it must be some power spike in the AC or noise on the network interface. However, the power strip and the UPS should block an AC spike and the chance of electrical noise in the cat-5 looking like a wake-on-lan packet seem more than miniscule. So again I ask you, dear AskSlashdot reader, WTF?! I await conspiracy theories, pseudo-science, wild rantings, and hopefully, the right answer."
This discussion has been archived. No new comments can be posted.

Fluorescent Lights Magically Activates iMac? More

Fluorescent Lights Magically Activates iMac?

Comments Filter:

  • Find the reason... (Score:2, Interesting)

    by Bladesnitz ( 75600 )
    Perhaps you can setup/run some kind of program that will tell you what exactly is bringing it out of power-save mode... I'm not familiar with any, but I'm sure one is out there... and if one isn't - I'm sure it can be written! : )

    If you find out its a WOL... make sure your neighbor isn't peeking through the window just to screw with ya!

  • Hmm. (Score:3, Funny)

    by NoMoreNicksLeft ( 516230 ) <john.oylerNO@SPAMcomcast.net> on Saturday May 18, 2002 @04:01AM (#3541863) Journal
    Well, since this is a somewhat useful behavior, I believe I am correct when I say that this rules out hidden M$ software completely.
    • Way to get in that supposedly-obligatory MS potshot in a post, but why is turning on one's desk lamp and having it activate my computer useful behavior? If I want to write a letter at my desk, and don't need my PC, this behavior is actually kind of annoying. If I want to work on the computer, I'll touch the keyboard/mouse.
      • If you don't find it useful, then quite possibly it is MS Office for Mac somehow.

        Seriously, I agree with the other poster, that this is probably line noise on the cat5 cable. Some rearranging plugs, etc should be able to figure out what will cause it, what won't. May not get the explanation you want, but seems like you'd at least know "if the lamp is over there, it doesn't happen".

  • Cat-5 noise (Score:3, Informative)

    by PsndCsrV ( 80030 ) on Saturday May 18, 2002 @04:02AM (#3541865) Homepage
    My guess would be cat-5 noise. I've had problems with my computer turning on erratically whenever I plugged/unplugged a port, or jiggled a loose connection. For whatever reason, the noise on the network woke it up. I finally just turned off WOL, since I wasn't really using it for anything... just playing.

    Try putting more distance between the hub/switch and the light, and see if it still causes it to happen. I wouldn't imagine the light could cause much interference over more than a few feet or so. You might also try hooking up another machine, and monitoring all the electrical activity on the network. Myabe something will poke up.
    • Yeah I hate unshielded cables as well. Why the fuck does everyone use them?
      • ALL Cat5 cable is unshielded. You could go back to coax if you want shielded ethernet.

        • Re:Cat-5 noise (Score:3, Interesting)

          by Tuzanor ( 125152 )
          There is such a thing as shielded Twisted Pair (Cat5). Though people rarely impliment it properly. They forget (actually, they probably don't know) that you have to ground the shield in order to properly shield the inside wires.

          • Exactly true. Shielded Cat-5 is more expensive. It is more difficult to find a supplier. And, in this case, shielding would almost certainly not help. The noise is definitely not coming from some electromagnetic connection with one wire inside one of the twisted pairs.

            The problem is probably a ground loop; probably the noise is being conducted along the ground wires. More directly grounding the components to each other may help.

            Also, it seems to me that Wake-on-LAN is a technology that is usually not implemented well. I've seen cases where it was a selling point, but caused problems.

            One thing that helps stop Cat-5 noise is grounding the unused four wires. There are 8 wires in Cat-5, and only four are normally used. (It is possible to buy adapters that allow one Cat-5 to carry Ethernet for two computers, but that is not normally done.) There is electrical capacitance between one Cat-5 pair and the others. When you ground the unused two pairs, you are grounding most of the common-mode noise that would otherwise be experienced on the two pairs that are used. In a low-noise environment like the one mentioned, grounding the unused wires would be the equivalent of having shielded Cat-5. This is something you can try without cost if the Ethernet signal travels through an accessible wall or other connector.

            However, as I said, the problem sounds to me like noise conducted along the ground wires, a "ground loop".

            • The problem is probably a ground loop; probably the noise is being conducted along the ground wires. More directly grounding the components to each other may help.

              It may just be my universe, but I don't ever recall coming across a grounded fluorescent lamp. That, and none of the wires in ethernet is ground... there's a differential TX pair and another differential RX pair, the rest being unconnected.

              I would be willing to bet that it's a noise spike getting misinterpreted as a (bad) ethernet frame. UTP is generally pretty good at ignoring common mode noise but but without really getting into the details of the problem I can't say whether the noise really is common mode or just "almost" common-mode.

              IMO WOL should only wake on a good packet destined for the MAC of the sleeping computer, but it appears that it's just another broken technology.


              • Yes, but how is the noise signal getting into the computer? Generally, there is some problem with the ground. The noise from outside wags the entire computer around because of the bad ground.

                If there is a bad ground, the noise on the ground side can overwhelm the common-mode capability of the differential pair.

                • Someone wrote the following e-mail message to me. I decided to remove his name and company, but post the messages, so that everyone could benefit.

                  ______________________

                  G.T. wrote:

                  Just read your slahsdot posting on CAT5 cables. I am at the moment constructing an ethernet to fiber converter for long haul applications.

                  I have been looking at various application notes from different ethernet chip companies, and I have noticed that some (but not all) designers does just what you writes: they connect the unused ethernet pairs via a resistor to ground, and after reading your post I finally understood why ....

                  Soooo, where did you learn this? I have read (or browsed trough) the IEEE ethernet standards, and have not seen this anywhere. I believe that there are other tricks like this that I really should know. Do you know of any good resources for ethernet from a hardware point of view ?

                  Best regards

                  G.T.

                  ____________________________________

                  G.,

                  I am happy to help. The attached information is very difficult to find on the internet. That's why I carefully saved it to PDF files. If you need more information, let me know.

                  My information about the likely causes of problems with noise comes from having been an electronics circuit design engineer. You would not use a resistor to ground the unused Ethernet pairs, that would defeat the purpose a little bit. You would ground them directly. You can ground two wires, one from each pair, at one end and the other two at the other end. You should not ground any wire at both ends, because there may be a voltage difference between the two grounds.

                  My experience with 100 BaseT Ethernet is that it is generally problem-free. That's what led me to suspect a problem with grounding. Something is overcoming the common mode noise rejection of the Ethernet receiver, I guessed. That is most likely to be a loose ground. For example, maybe the computer in the Slashdot example is not grounded at all. It could be that the outlet to which it is plugged has a bad ground connector. I would suspect something simple like that.

                  Often with ground problems, people have symptoms which cause them to look in the wrong place. Before I was a design engineer, I was a repair technician. I repaired aircraft automatic flight control systems. One day an aircraft came in with 4 very serious malfunctions. Partly lucky and partly smart, I said, hey, wait a minute. I don't believe 4 malfunctions happened in one flight. I began to look for one thing that could cause all 4 malfunctions. The only thing they had in common was the ground. I told the crew chief to look for a bad ground. They found that someone installing some equipment had not remembered to re-attach the ground to the entire bay of equipment.

                  Again, it seems reasonable to repeat that Ethernet and 100 BaseT are very well-designed, robust technologies. Anyone who has problems should suspect something simple. Shielding of the Cat-5 and grounding of the unused pairs is only necessary when the noise is extreme, such as when doing arc welding 1 foot away.

                  Regards,

                  Michael Jennings
    • It could be this. A WOL packet is a broadcast with this structure
      FFFFFFFFFF
      My-MAC-Add
      My-MAC-Add
      My- MAC-Add
      My-MAC-Add
      My-MAC-Add
      My-MAC-Add

      and your mac might be responding to that

      That would be one hell of a coincidence for your lamp to generate that packet! I'd get the ballast and tubes replaced.

      Pi
      For Great Justice|ecitsuJ taerG roF

  • logical process... (Score:5, Insightful)

    by invictus ( 83837 ) on Saturday May 18, 2002 @04:10AM (#3541876) Homepage Journal
    one way to go about figuring it out, i would think, would be to remove the mac from the lan, turn on the lamp... does it wake up? if it does you can rule out WOL. If it doesn't, then it seems to be something on the network. Is the hub/switch plugged into the same surge protector as well as being perhaps too close? just step through the problem.

  • i had this problem once... (Score:5, Funny)

    by jnana ( 519059 ) on Saturday May 18, 2002 @04:13AM (#3541884) Journal
    it turns that some of my body thetans [xenu.net] had gotten trapped at the electrical outlet, and any kind of a disruption to the old AC current would cause them to send out signals that would wake my laptop. I couldn't figure out what was going on, so I called my counselor at the Church of Scientology. He sent over some of their scientists, and they turned my place upside down with a special device, like an e-meter, that detects escaped body thetans. I'd recommend you give them a call. It'll only cost you about US $15,000.

  • Easy fix (Score:4, Funny)

    by lightspawn ( 155347 ) on Saturday May 18, 2002 @04:21AM (#3541896) Homepage
    Just pop in Celine Dion's "copycally-challenged" CD before you turn off the iMac.

  • Does it have IR port? (Score:4, Interesting)

    by marat ( 180984 ) on Saturday May 18, 2002 @04:24AM (#3541901) Homepage
    Probably it's receiving some nonsence data when you switch on the lamp. Also, UPS might be trying to tell you something via it's COM port connection or whatever. Network interference via switch is also possible. Plug out one by one and check.

    My PC turned on after any phone ring (very disturbing while installing some new hardware :( ) though they was not 'Wake up on ring' option in BIOS. Turned out that 'Wake up on LAN' also works as 'Wake up on ring'.

    BTW does you mac have external modem? Probably your modem tells RING each time you turn on the lamp. Easy to check with any terminal program.
    • My PC turned on after any phone ring (very disturbing while installing some new hardware :( )

      I don't want to sound obvious, but, did you ever try unplugging the computer before installing new hardware?
      • you lose your ground that way. having everything grounded cuts down on the risk of static electrical discharge. you really should turn your power supply to off, though.
        • That's only true for old computers. Modern PCs have standby power (needed for wake-on-ring and wake-on-lan), and so parts of the motherboard will always be powered as long as the computer is plugged in. Your motherboard manual will usually tell you to unplug the computer when installing new hardware.
          • Isn't that only if the computer is off with the power supply switch still on? If the power supply is physically off, I don't see how the computer could turn on. Soft-mode power only works if the power supply allows you to turn it on. With the switch off, I don't think you can. That's why you can intercept hitting the power button on your computer, but not when you flip the switch in back.

            I could've sworn, (been a while, haven't needed to open any cases lately), that the green LED on the MB that is usually lit when the power is off, actually turns off when you flip the physical power switch on the power supply. It just takes a second or two for the LED to discharge the electricity from the capacitor.
            • Isn't that only if the computer is off with the power supply switch still on?

              It would appear that the ATX power supply predates the ATX power supply switch by about a year, depending on manufacturer.

              A lot of those first-gen ATX power supplies had severe reliability problems as well (I've seen batches with %20+ failure rates after six months), so they're increasingly rare.

    • About 6 years ago, A teacher at my HS told me a bizzare tale of her computer turning by itself all the time. Turns out it was a mac, At the time Apple was shipping "Performa" series macs with an IR port on the front. After disabling the IR control panel it never happened again. I imagine that most laptops come with an IR port, and disabling it or using the black tape method will solve the problem.
      • we had one of those Performa's. For a while it was on the same floor as the TV system. One day, as I pointed the remote in the general direction of the Sony TV, it magically "pwong'ed" and started up!

        It was sort-of useful, mostly fun though. Tape over that IR port and test it!

  • EMI (Score:2, Insightful)

    by Anonymous Coward
    My cordless-phone (900Mhz) base is about 2 feet above my DSL bridge and hub. Any time there is activity on the ethernet/DSL and I'm on the phone, I can hear it as noise. On certain channels, the noise is more prevailant. Which means either the channel's frequency or one of its harmonics is near the frequency of the ethernet/DSL or one of its harmonics and the power is significant enough to be picked up by the phone. I would guess that a lot of power is needed to first "start" the flourecent lamp. The big "spike" causes enough EMI that your ethernet cable "picks up". The ethernet cable is then acting like an antennea. The wake-on-lan must just detect ANY activity on the ethernet, not a valid packet. Anyway, that's my guess.

    • Format of a Wake-On-Lan Frame (Score:5, Informative)

      by uofa1993engrmath ( 564313 ) on Saturday May 18, 2002 @05:30AM (#3541988)
      > The wake-on-lan must just detect ANY activity on the ethernet, not a valid packet.

      IBM has a White Paper, Wake up to Wake-on-Lan [ibm.com] which describes the specific format of a Wake-Up packet (6 bytes of F (XX'FF') followed by a 48-bit target address repeated at least 8 times). Even if the target address was a broadcast address, I don't see how this could be reliably generated by the starting of a fluorescent lamp. Plus, your average LAN has a whole bunch of traffic going on all the time anyway.

      I have an iMac DV (graphite), and I DON'T have it plugged into a network, and it's NOT configured for Wake-on-Lan, nor is it configured to wake on phone rings, and I don't have any infrared devices that I know about, and I have an optical mouse, so it won't wake if the mouse gets moved, and it still wakes up when I vaccum my living room or turn on my slide projector.
      • Vacooming creates a lot of static electricity. Probably same for slide projector though I don't know how. I know (not properly grounded) ATX computers that sometimes turn on by just a static discharge after touching them.
      • Interesting. But do you think that perhaps instead of taking the extra hour to add in the code necessary to actually watch for and parse the packets, the designers just said,

        "OK, look. If there are any voltage changes on the line, there's a 90 percent chance it's LAN activity. We'll have it wake up then. Hey, it's Wake On Lan, innit?"
      • I have an iMac DV (graphite), and I DON'T have it plugged into a network, and it's NOT configured for Wake-on-Lan, nor is it configured to wake on phone rings, and I don't have any infrared devices that I know about, and I have an optical mouse, so it won't wake if the mouse gets moved, and it still wakes up when I vaccum my living room or turn on my slide projector.

        Obviously, iMacs get jealous whenever another electrical device in the room gets used. "*sniff* there he is, vaccuming again. Maybe if I turn myself on he'll come play with me."

  • I don't know about you, but fluorescent lights always put me to sleep.

    Anyway, Compact Fluorescent lights have been known to interfere [gelighting.com] with IR devices and radios. Like others have said, I would guess it's probably just putting out a lot of noise.

  • does it (Score:5, Funny)

    by fferreres ( 525414 ) on Saturday May 18, 2002 @05:00AM (#3541942)
    come with a compact flash reader? Oh...

  • Airport? (Score:2, Interesting)

    by theCat ( 36907 )
    Here's a fun one: If it has an Airport card installed then maybe it's waking on wireless LAN, getting a random ping from the desk lamp. But since you are already using CAT5 we can rule that one out, right?

  • Mobiles phones (Score:4, Interesting)

    by cowbutt ( 21077 ) on Saturday May 18, 2002 @05:30AM (#3541985) Journal
    I woke up early one morning to the sound of my electronic metronome going tick-tick-tick-tock quite loudly. My first thought was that I'd somehow managed to leave it on before going to bed and sleeping right through it. When I checked, I found that my old Nokia 6150 was charging right next to it and the aerial was pointing right at it.

    My guess is that one of the periodic cell checkin transmissions induced enough of a current in the on/off circuit that the metronome decided to switch on. Spooky!

    --

  • mouse + light (Score:5, Insightful)

    by daniel2000 ( 247766 ) on Saturday May 18, 2002 @06:09AM (#3542051)
    if you have a mouse anywhere near the light and then some light could be getting into the mouse makeing it think it has moved.

    Try the experiment with the mouse covered up with a rug and switching the light on.

    I had an experiance where at certain times of the day the mouse cursor would go a bit funny. took a while to work out it was when the sun peeped throught the window at just the right angle...
    • Haha, sorry, I just can't help myself from laughing -- does he really need to use a RUG? I can just imagine a big old rug on his desk covering the mouse. How about a bathroom towel? Or unplug the mouse? Poor guy will suffocate with an entire RUG on him!
      • Yeah, i guess that is kinda funny, i guess you are taking rug as a peice of floor carpet or something?

        I guess rug has slightly different meanings in different parts of the world. (over here we often just use it to mean a cover. eg: blanket or even a jumper / shirt eg: dont forget to rug up! meaning don't forget to put a jumper on its cold outside!)
    • If you have a laser pointer, you can flip the mouse over, and point the laser at the optical pickup, and make a really really crude optical joystick.

  • Re: (Score:2, Interesting)

    by account_deleted ( 4530225 )
    Comment removed based on user account deletion
    • Try plugging your fluorescent lamp into the UNprotected outlets on the UPS. Though it is convenient during power outages to have the lamp powered from the UPS as well as the computer. Simply change the plug back when that happens.
  • are you using an optical mouse?
  • As kid I used to have a C64. After some years its power supply was slowly dying and it became more and more instable: electric equippement like a vacuum switched on nearby caused it to crash or made it reset. But the /really/ funny thing is that flushing the toilet next to my room caused a reset---and that nearly 100% repeatable.

    It was one of those old style toilets whith a big water tank high above the seat and if you pulled the trigger a huge amount of water caused a "whoosh" that would have made Al Bundy happy...

    I think I worked around the problem by stabilizing the reset line with a condensor or so. Then the power supply finally died, so I played with 6V batteries to power my C64 and one day accidently killed it somehow :-(. IIRC the toilet has gone by now as well.

    I have no clear idea that the physics behind that was: Was it the same effect that made rising/falling raindrops cause thunders? Or did the quick movement of a large mass of (soemwhat) electric conductive material disturbed the electric field?

    BTW: Switching on the light+fan in the toilet had no effect on the C64.
    • Of course, maybe it could be as simple as having an electric-powered pump and a well that provided that toilet with water.

    • I think I worked around the problem by stabilizing the reset line with a condensor or so. Then the power supply finally died, so I played with 6V batteries to power my C64 and one day accidently killed it somehow :-(. IIRC the toilet has gone by now as well.

      You'd have had to use more than 6V batteries to get your C64 to boot; the power supply provided both DC and AC voltage (5VDC and 11VAC IIRC) -- I had built a power supply from a small transformer and some small gel-cell batteries since I had no decent 78xx regulators on me.

      • No. The 9 (not 11) VAC was only used (IIRC) to deliver a 50Hz (60Hz in other countries) time base for the RTCs built into the 6526 CIAs, to power the 'datasette' and to create an additional 5V voltage and 12V. Now I remember how I probably killed it: I fed the 12V to the wrong place...
        (I didn't need the datasette and the RTCs were rarely used anyway).

        But it depends on the models, later models didn't need the 9VAC at all and could operate on 5V only.
    • Nothing that exotic. I'd guess a cracked solder joint in the power supply causing a voltage fluctuation when the toilet flushed, and that's probably why the power supply died as well, when the crack turned into a break. I'd guess but don't know that the brick was plugged into the wall on the side next to the toilet, right?

      If you still had the thing, I'd say touch up the power supply PCB connections with a soldering pencil, or better, replace the 7805 3 pin voltage regulator at the same time.

      Used to work at a company producing C-64 software way back when, I had to fix some of those beasties... the C-64 really wasn't intended to run 18+/7.

      • > I'd guess a cracked solder joint in the power supply causing a voltage fluctuation when the
        > toilet flushed, and that's probably why the power supply died as well, when the crack turned
        > into a break.
        That was certainly not the case - other vibrations or shocks (e.g. shutting the door, moving the chair to the desk, hitting run/stop-restore on the keyboard, footsteps) would have caused it as well - but that didn't happen.

        The problem with the power supply was that it simply didn't provided the correct voltage. It was closer to 4V than to 5V.

        > I'd guess but don't know that the brick was plugged into the wall on the side next to the toilet, right?

        No, it wasn't. And further more: it was a brick wall, the power supply was on the floor, more closer to the opposite wall. Sadly, ASCII art is considered "lame" by slashdot's filtering system, so I can't provide a sketch from the room.

        Disclaimer: This is all from memory since it was 13-15 years from now.

  • Your UPS is sending a heads up ... (Score:4, Interesting)

    by kousik ( 149219 ) <`kousik.nandy' `at' `gmail.com'> on Saturday May 18, 2002 @08:21AM (#3542187) Journal
    Is your UPS connected to the network
    so that it can inform the machines
    when there is a change of status of
    power line? Maybe when the light is
    turned on, the power surge makes UPS
    send a packet to your network? Just
    guessing.

  • Lamp + Ethernet (Score:3, Interesting)

    by FreeMath ( 230584 ) on Saturday May 18, 2002 @08:46AM (#3542230) Homepage Journal
    Fluorescent lights cause horrible interference when placed within ~5ft of cat5. Flipping the switch on the light is probably overloading the NIC and waking it up.
  • When I was a freshman in college, my roommate had (I think) a Performa 6100. Every once in a while, the thing would just start blasting music for no apparent reason. We realized eventually that it was due to our other roommate using the remote control to his Sony CD player. When he pushed play on the remote, apparently the Performa, which had an IR port right in the front, intercepted the signal.

    Once we realized this, we had lots of fun tormenting each other by setting roommate #1's speakers all the way up and playing his CD at full volume while he was doing stuff. Nothing like hearing Jimi Hendrix's Band of Gypsies at max volume at 3 am!
  • unplug EVERYTHING but the power. i convinced my mom that my computer wakes up whenever a person sits in front of it. turned out, sitting in the chair made right vibrations to move the mouse just the *tiniest* bit -- effectively waking up the machine.

  • The answer (Score:2, Informative)

    by dr00g911 ( 531736 )

    The answer to your dillema is pretty straightforward: when you turn the light on, your *optical* mouse is noticing a change in the pattern on the desk, and interpreting this as the mouse being moved to wake the Mac.

    The way to test this hypothisis 100%? Unplug the optical mouse, let the bugger go to sleep, and turn on the light.

    Easy, neh?


    P.S. It does that in a few of my setups (I work in the dark, with a Kensington Flylight over the keyboard usually) -- but the Apple optical mouse seems much more succeptible than my Logitech cordless optical. Chances are this is because the Apple mouse is mostly transparent.

    • Another note: (slightly OT)

      The principles of Okham's Razor [panikon.com] almost always apply to tech support and troubleshooting.

      The simplest answer is, truly, almost always the correct answer -- or at the root of the problem.

      You can also call it the Tao of Tech Support if that sounds more pleasing, but if you follow problems to their most glaringly obvious potential causes, you're normally on the path to getting the problem fixed with minimal, er, resistance (couldn't resist) and energy expenditure.

    • The answer to your dillema is pretty straightforward: when you turn the light on, your *optical* mouse is noticing a change in the pattern on the desk, and interpreting this as the mouse being moved to wake the Mac.

      Well that would be a good answer... except that Mac's usually don't wake on mouse activity. For example, with every single mac in our office, wiggling the mouse does nothing. Hitting the shfit key is the prefered way to wake them up.

    • The answer to your dillema is pretty straightforward: when you turn the light on, your *optical* mouse is noticing a change in the pattern on the desk, and interpreting this as the mouse being moved to wake the Mac.
      Sounds good, but doesn't work for mac: if the machine goes into sleep mode, the optical mouse light shuts of. Moving the mouse won't wake the computer, clicking will do just fine.

  • I was once installing IP-forwarding on my secondary box to cleverly avoid paying extra for cable. So me and my friends were fixing and configuring. Then my firewall prompts that someone unauthorized is trying to send a packet to me. First I just thought "what?, this usually happens when I'm surfing". Then I realized we've put the cable-line on the other machine and my box was on an empty hub.

    I have stong reason to believe it had somethong to do with me having LOTS of electronics (15-18 appliances) plugged in my room.

    Back when i had a TV, the picture would sometimes shake when the fridge whent on (mind you, the fridge is in the kitchen, a totally different room).

  • Studio displays. (Score:3, Interesting)

    by saintlupus ( 227599 ) on Saturday May 18, 2002 @11:34AM (#3542543)
    I've got a 15" LCD Studio Display on my machine at work. The walkie-talkies that the maintenance and security staff use will activate the power button on it, turning the entire computer off if someone is walking by and their radio receives a broadcast.

    Ever get the feeling you're being _bathed_ in RF?

    --saint
    • If you haven't already, contact Apple.
      There's an issue where the wiring gets shorted out on the PowerSwitch of the LCD Monitor.

      An AASP can re-wire the monitor, or Apple can setup a Mail-In Dispatch Repair.

      1-800-sos-apple (800 767 2275)

  • Its just being friendly! (Score:1, Funny)

    by Anonymous Coward
    It seems that your older iMac is mistaking the desklamp for one of the new generation iMac's
    (afterall, they look like desklamps anyway)
    (from visual_bob@hotmail)
  • My C64 crashes when I turn the fluorescent lights on or during lightning. The board in that home computer is shielded only with an aluminum coated piece of cardboard and lightning and the ignition of fluorescent light tubes give off a strong blast of electromagnetic energy in a broad spectrum. I suspect that is what is hitting your Apple home computer
  • I have a GSM (Fido) cell phone which I sit on my desk when I'm at home. The funny thing with GSM is you can hear it communicating back and forth with the network just by holding it near a speaker. Just leave it somewhere close and you'll hear this rythmic noise every once in a while.

    Whats really interesting is that my door bell goes off just before my phone rings (1/2 second or so). I have a little Radio Crap wireless one, and it ALWAYS (100%) goes off just before my phone rings, if my phone is close to it. Kinda creepy the first few times it happened.

    Theres a LOT of sources of electronic noise out there, it's pretty funny when stuff like this happens.

  • PEBKAC (Score:5, Funny)

    by KFury ( 19522 ) on Saturday May 18, 2002 @12:57PM (#3542857) Homepage
    This is a new iMac, right?

    Okay, look in your office, and put your hand on the lamp. Is your hand resting on the thing with a rounded base, a stalk, and a flourescent emitter at the end? That's your computer. Don't worry, a lot of people make that mistake.
  • i woudlnt complain to much.
    walk in hit a switch computer and light go on.
    i usualy work with a lamp on anyways. one less button to push later.

  • Some funky (Score:3, Informative)

    by Graymalkin ( 13732 ) on Saturday May 18, 2002 @04:09PM (#3543532)
    The Cubes had a similar problem to this, for some reason the power switch circuitry was susceptible to RF noise generated by flourecent lights and other noisy electrical devices. Other G3 iMacs have also demonstrated their weirdness. It isn't static on the electrical wiring itself but RF noise being generated by the RF generated by the flourecent light. Call up Apple and ask them in there is a tech article about the power switch RF interference problem. It's a probablem that cropped up in a couple of different Mac models though not necessarily all of those models.
  • I had a friend in college who was given, as a joke, one of those clappers (Clap On...Clap Off...Clap On Clap Off....). So he plugged it in an forgot about it, until a guy down the dorm hall got a new stereo system and liked to turn the bass way up. Suddenly my friends lights started flash on and off all night....the thing picked up the vibrations through the building!
  • Energy saving fluorescent tubes emit light alon the infrared spectrum. I see this all the time at work - the infrared interferes with the remotes for some of our products. Try an incadescent lamp of the same power consumtion specs, or disable your IR port.
  • They put out a lot of RF garbage. IIRC there was an early mainframe that was put out of action by a florescent fixture. Keyboard or mouse most likely gets a signal that gooses the computer.
  • Since some people were posting about the strange stuff too, here's mine:

    My home PC came with no less than two sets of crappy speakers. (As a music lover, this insult was severe enough to make me decide to buy the next PC in parts =)

    Anyway, one set of the speakers was supposed to be attached to the monitor somehow (more cabling than anyone ever needs).

    I plugged the speakers in. I couldn't hear a thing.
    I unplugged it. It worked.

    I used the speakers from my old PC, and now I have a nice 4.1 speaker set - so that... I... don't... need to... think... of the... haunted... speakers... in the... *shiver* box... in the... cellar. *shiver*

    Maybe I won't sleep that well tonight, now that I was reminded of this thing...

    • Was that a Proview or EMC brand monitor by chance? If so I might know why they worked after being unplugged.
    • you've got a broken amplifier in the speaker. when you remove power, the speakers are basically running off the power from the soundcard - they won't get very loud, but they'll still work (try plugging a non-powered speaker into your headphone ajack sometime). when you give it power, whatever is broken in the speaker's amp prevents it from working at all.
  • Or a standby power supply?

    Most vendors are confusing the term UPS. It once meant a power supply with your computer _always_ receiving power from the batteries, while the batteries were being recharged from the mains.

    Nowadays a lot of vendors use the term UPS to mean that power is taken directly from the power lines to both the computer and the batteries when availiable. When the power goes out a relay drops out and switches the computer from the mains to the batteries.

    Basically the first type always provides perfect power (assuming the inverters generate a sine wave -- many do not), whereas the second type provides nothing more than power filtering unless there's no mains.

    While filtering is usually better in a UPS than in a $5 power strip, it doesn't filter everything. To prove this, hook up an intercom that uses the AC to transceive to your UPS and see if you can communicate with another at the wall plug.

    Unless your UPS uses some form of solid state relay (not likely) you can test if its the "real thing" or not by pulling the power and listening for a click inside the UPS. If it clicks, you have a standby power supply.

    Not that the noise from the one lamp should _really_ affect the other, but hey, I don't own one. :-)
  • I could see a new imac [apple.com] waking up when its desk-lampian cousin was turned on, but an imac DV is out of the question!
  • Not sure if that model has an infrared port...put would that kind of light [startup flicker?] produce any/enough of that spectrum to tickle your infrared receiver?
  • Fluorescent Lights Magically Activates iMac

    Fluorescent lights cause RF [interference], I would suspect that is raising a rail in you network cable.

    We use large numbers of ADSL modems pushed towards there upper bandwidth limits to serve a digital TV project. As you can expect some of our hardware enginners have become real experts in the field of RFI and crosstalk. We had a particular set of problems that could not be tracked down, crosstalk was supected and test gear indicated RF interference on the lines.

    However further tests revealled crosstalk was not the cause, the RFI spikes occured in exchanges that had not even been xDSL upgraded and somebody noticed when the engineers entered the exchanges, the situation deteriorated and QoS problems got worse. The network management systems reported thoughput and packets dropped. This was before the networking had been touched the, after much head scratching the problem was discovered as the Fluorescent lights, they had to ve removed from every one of our exchanges because of the RFI problems they cause.
  • Generally, most UPS's today don't do anything to condition the line. While you have AC power that falls within "normal" ranges, you're literally getting line power just as if you were plugged into the wall. The UPS isn't doing anything to filter noise here. Now, if the voltage were to drop or rise outside of the normal range, the UPS should generally kick in and get you onto battery, but I don't think that would be happening here (you'd notice).

    Similarly, power strips generally do nothing to protect you from anything except too much current. Voltage can drop way below or rise way above normal and the power strip would keep supplying this power. If your power strip doubles as a surge suppressor, you might get some protection from voltage spikes in addition to too much current, but don't confuse this with a real line conditioner, which would remove noise from the power as well and guarantee you a clean power source.
  • Take a ferrite [pcworld.com] (that little plastic doohicky that protects monitor cables from RF interference...you didn't throw it away, did you?) from an old monitor cable, and put it on the ethernet cable - if you can't find one, they are available at electronics shops for a nominal price. That might do the trick...
  • Power spikes seem to do this with the Macs. Turning off my USB printer will wake it up. On rare occasions turning off the screen when the computer is asleep will also do this.

Slashdot Top Deals

"Look! There! Evil!.. pure and simple, total evil from the Eighth Dimension!" -- Buckaroo Banzai

Close