Computer goes through power cords?

Discussion in 'Mac Pro' started by 76ShovelHead, Jun 14, 2012.

  1. 76ShovelHead macrumors 6502a


    May 30, 2010
    My computers (Hackintosh, eMac, and iMac) have all once in their lifetime refused to turn on, and a new power cord fixed the issue. Today, my Hackintosh did just that. I spent like two hours trouble shooting why it wouldn't turn on. Opened it up, unplugged the cord, re-plugged the cord over a dozen times, and yet nothing worked until I pulled out a spare.

    Has anyone else ever had these issues with their computers? I'm starting to think (google search returned no results) that my house has some messed up outlets/wiring. Thing is, I replaced all outlets in my room 2 months ago with shiny new white ones. It cant be a coincidence that all my computers have power supply issues!
  2. Buffsteria macrumors regular


    Jun 9, 2012
  3. Zwhaler macrumors 604


    Jun 10, 2006
    Never have had an issue with power cords on my year old Mac Pro, or my almost 6 year old iMac Core 2 Duo, or any of the laptops, or Mac Mini.
  4. pprior macrumors 65816

    Aug 1, 2007
    I've been buying (lots of...) electronics for probably 20 years that have used the standard "computer" power cable - audio stuff, computers, various other things. In fact I've thrown away bags of those cables that have collected/duplicates.

    In all that time, I've NEVER had a bad one.

    I kinda don't believe you're having that problem either. If you have that bad of an electrical problem to destroy a cord, you're going to fry the rest of the comptuer before that.
  5. thefredelement macrumors 65816


    Apr 10, 2012
    New York
    When you replaced your outlets how were the wires? Frayed? Burnt? Crumbly? Did they fall apart a bit and did you have to strip some of the insulation off to get to good copper? Or is the faceplate hot to the touch or the end of the power cord, by the plug, really hot during use?

    The only thing I can think of, is a lot of load by your outlet where you plug your computer in to and so much heat generating by the outlet that it's making the plug end of the cord really hot and melting/breaking something where the prongs turn to wire. This could be caused by a lot of load on the outlet itself or somewhere close to it on the circuit.

    I did electrical work for about 4 years in my younger days and while I've owned computers for the last 18 years, plus my electrical knowledge, I've never seen anything or heard of anything like this.
  6. Just Switched macrumors member

    Aug 7, 2008
    This situation if true is probably beyond the scope of what a typical electritian or computer hobbyist would be able to answer. I can't think of a single situation were power cables are constantly going bad with any damage to the computer except for physical abuse to the cable. An electrical engineer however would probably know exactly what's going. Again this does sound odd indeed.
  7. saulinpa macrumors 6502a

    Jun 15, 2008
    Happens when people continually pull the cord out by yanking the cord instead of grabbing the plug.
  8. d-m-a-x macrumors 6502

    Aug 13, 2011
    weird!! i still use a plug from the og G4
  9. Cindori macrumors 68040


    Jan 17, 2008
    I think after 10 years of computing, power cords are the only component that has never failed on me...
  10. paulrbeers macrumors 68040

    Dec 17, 2009
    Agreed. I have so many from computers that cease to function (and other electronics) that when we moved recently I had to pitch at least a dozen.

    It is possible that the OP is using undersized power cords (i.e. a power cord for an LCD monitor tends to be thinner than say a power cord for a 1000watt power supply). However, this is purely speculation....
  11. 76ShovelHead thread starter macrumors 6502a


    May 30, 2010
    After first moving in, I plugged my iMac into one of these outlets and after a few minutes it just shut off. Wouldn't turn back on until I moved to a different outlet. Since this incident I stopped using this outlet, until 3 or 4 years later when I replaced the outlet to find the disconnected ground wire. So to be safe I replaced both outlets in my room.

    I am using a couple power strips, none of the new outlets are hot. I thought it could have to do with my power supply, but given the history of the electrical outlets in this room and the amount of computers to do this. It is strange.

    To address the people who have a hard time believing this:

    The cords aren't melting or anything. They just stop working with the computer. No matter how many times I unplug them from the computer and replug them. Yes I have checked the switch. After reseating the power cord several times to no avail, I plugged in a new cord and it worked. I have had this happen to me on the eMac as well. Although the cord needed to be changed, there have been cases where I used the cord on another electronic and it still worked.


    I never considered this. The cord I changed was smaller than the one I replaced it with.
  12. Comeagain? macrumors 68020


    Feb 17, 2011
    Spokane, WA
    Can you use the old cables with something else? Do those work as expected?
  13. Thessman macrumors regular

    Dec 8, 2005
    I'll double that but for 30+ years of computing :p
  14. Bug-Creator macrumors 6502


    May 30, 2011
    Even at the low voltage used in the US (110V ?) we would still be talking bout single-digtit amperes (well the math isn't that simple with AC but he is surely not useing an 1000W PSU at 1000W).

    Cables could be really thin before the would be melting (and they would also show physical damage on the outside).

    Moreso here in Europe these cables are defined by the fuse normally used for the outlet (16A) and when it comes to grounded cables I haven't seen anything smaller than 1.5 mm^2. (ungrounded cables are often thinner, but still atleast 0.5 mm^2).
    An overloaded cable would sure feel pretty warm.

    What might be an issue is the contacts in the actual plugs corroding due to moisture or the electronic going out whack to due undervoltage and greating "blind" current (not sure how to translate that, just when voltage and current get out of phase, resulting in massive amounts of energy travelling back and forth between the PSU and the powerstation). But that again would mean warm cables&plugs.
  15. pprior macrumors 65816

    Aug 1, 2007
    Cords are pretty simple. If they're not frayed (which would be VERY unlikely given the design nowdays) then they're pretty much foolproof.

    Stick an ohmmeter on one of the "bad" cords. My guess is that they are fine. As noted above - do the cords worth with other electronics?

    Have you checked the male side of the plug on the computer - is it possible something got pushed up in there or is damaged?

    This whole thing is very strange. I don't have any reason to doubt what you're posting is happening, but the odds of having multiple cords go bad are infitisimal, imo.
  16. G51989, Jun 15, 2012
    Last edited: Jun 15, 2012

    G51989 macrumors 68030


    Feb 25, 2012
    NYC NY/Pittsburgh PA
    Man. I can't see how thats possible. I've NEVER had a standard Power Cord fail on me. Ever. Some of them are a solid 20 years old. Still no failures.

    There is a pretty good chance your PSU is going.

    I once had an generic HP XP box that did the strangest thing, just randomly refused to boot up. But, what you could do, is unplug the power cord from the PSU, turn the PSU back on, hold down the Power Button, and plug it back in, there would be some nice sparks :D. And it would just boot right up. Never figured out why
  17. thefredelement macrumors 65816


    Apr 10, 2012
    New York
    If you're able, I'd run a new line to that room from the breaker box and loop your outlets in to it.

    I'm not sure how a ground problem could lead to bad power cords, really grounds aren't needed unless there's a problem and most of the power is returned via the neutral (they both go to the same place in your breaker box).

    It could be the ground is "broken" or not connected really well somewhere along your circuit. - You'd be the surprised the stuff that you see doing electrical work, even for a few years, in regards to some weekend warrior wiring.

    Any of these problems really make me think that you'd have power supply issues long before any cord would fail.

    If it's a Mac pro, and it's your pro desktop work space, get a new line run to the room with it's own outlet and branch off from there. At some point you'll recover your investment by not buying new power cords :) (maybe 70, 80 years lol)

    Other than that, if you replaced the outlet and it's fine, and the wiring is fine, then maybe it's the power strip that you plug in to, has it been the same one through out all of these problems?
  18. JavaTheHut macrumors 6502


    Aug 15, 2010
    Second that stick an Ohm meter to see if there is continuity.

    Question does the OP own a cat?
  19. thefredelement macrumors 65816


    Apr 10, 2012
    New York
    I was just thinking the same thing, I had a dog that loved to chew on power cords, I have no idea why...

  20. d-m-a-x, Jun 15, 2012
    Last edited: Jun 15, 2012

    d-m-a-x macrumors 6502

    Aug 13, 2011
    check for corrosion - sulpher, bad air conditioners could do it. would show up on the leads.

    Recently, i had to clean the leads on a dimm board because the ram was not showing up. Worked like a charm
  21. dwmc macrumors newbie

    May 15, 2012
    As someone that works on the design, implementation and testing of a device that draws 6 to 16 amps (16A only in IEC regions, not North America) of current from AC mains for long periods of time, I can assure you that power cords can have problems. There are tons of cheaply (and some shoddily) made power cords. For the poorly made units, it doesn't take a lot of heat to cause problems. I'm sure many of you have seen this kind of thing happen with an extension cord at some point in your life. A connection with higher-than-optimal resistance (male plug to outlet, or female plug to your power supply) can generate a significant amount of heat. It doesn't take much resistance if the current is high.

    The typical cheap power cord's contacts are almost completely fixated by the thermoplastic. There is a fixating cage that holds them in alignment while they're being molded, but it's not really part of the mechanical design other than holding the contacts during molding. It's a flimsy piece. When the cord gets warm/hot, the contacts have a lot of freedom of movement due to the thermoplastic softening. Aggravated if the cord is under off-axis tension, of course. And it tends to be an escalating kind of problem over long periods uf use; more heat means more contact movement, more contact movement tends to lead to higher resistance, more resistance means more heat. Severe enough, you eventually wind up with failure.

    Much of the time, the problem originates at the plug to mains outlet connection. For example, 40 year old outlets that have high contact resistance for whatever reason (corrosion, mechanically damaged contacts, etc.). I've rarely seen problems at the other end for devices that are stationary nearly all of the time, as long as the original cord or one of equal or higher current rating is employed. These cords are typically (but not always) UL or ETL listed and hence are third-party validated for their intended application. But... I'd put my hand on the cord and both ends to feel for heat as a start. It's entirely possible something is wrong on the primary or secondary side of your power supply that is causing too much current to be drawn. And/or that you've been using cords that were intended for lower current, or were built poorly, or previously damaged, or...

    I suppose it's also possible that your power supply is heating the plug for other reasons... fan(s) need replacement, or heatsinks are all covered in dust/smoke tar/whatever, etc.

    I guess my whole point is that heat damages cord ends, and the amount required to damage them depends on the cord. If you want to investigate, start by feeling the cord ends at cold boot and over the next two to four hours of normal use. If it were me, I'd investigate... I would not want a situation where fire could be a potential result.
    If you have an ammeter, use it. If you have an IR temperature gun, use it.

    Hope this helps. I've left out a ton of stuff in the interest of time and space, but hopefully given you enough to at least check the basics and make you sleep easier.

Share This Page