Power supply fried, replaced it, computer won't start

Discussion in 'Computer Support' started by ., Aug 28, 2006.

  1. .

    Guest

    wrote:

    > It lasted about three weeks, or the first power fluctuation - Lost the
    > power supply and mother board.


    And while your forking out the hard earned cash on a good PSU, get a
    good UPS as well. What's the point of a nice PSU if you have dirty
    power coming into it? :(

    > Just agreeing with you, One should not scrimp on the power supply, buy
    > the best.


    And don't be a cheap bastard when it comes to protecting it, either.

    Tripplite/APC are your friends, get a UPS, be a happy person. No power
    flucuations. The nicer ones always run your box on an isolated circuit
    actually fed by the battery. A true square wave is what you want to
    shoot for.
     
    , Sep 2, 2006
    #41
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  2. .

    Guest

    David Matthew Wood wrote:


    > Yes, and while it doesn't directly have anything to do with Power Good,
    > such power supplies don't provide any protection either. If you try to
    > fire up a GOOD supply and it doesn't observe the correct loads (either
    > from not being properly connected or from something that is shorting),
    > it will shut down in order to prevent damage since it is bad for a power
    > supply to run without a load. Same goes with amps. If you power up an


    Who told you such nonsense? A power supply isn't like an Amplifier,
    well, it sort of is electronically, but running one without a load
    isn't going to hurt it. Your not increasing voltage, your dropping it!

    > amp and crank the volume without speakers attached, it will either a, go
    > into thermal shut down, or b, self-destruct.


    Not the same concept... And this mainly applies to radio equipment and
    some poor quality amplifiers. It's the SWR I think that your talking
    about. Firing up a cb radio for example with no antenna and
    transmitting can damage the finals (transistors...)... but, for
    receive, it doesn't hurt anything. Just don't key the mic. :)
     
    , Sep 2, 2006
    #42
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  3. .

    Guest

    David Matthew Wood wrote:

    > What, that cheap POS power supplies don't shut down right away if
    > something is shorting? Well lets see. I have some sitting around that


    Some power supplies shut down when the voltage request goes too high;
    IE: ground out condition, sure. Some do not, some will fight by
    increasing available amps until something gives.. These power supplies
    think your just requesting more power.

    > will not power up at all because something in the machine shorted them
    > out. I have others sitting around that still power up and work just
    > fine after being shorted out, because they shut down right away before
    > damage was done.


    I suspect if you pop the case on a bad one and go probing, you'll find
    a blown diode is causing the power supply to play dead.

    > Shutting down before damage is done you mean. I've witnessed both.


    Damage with electronics can happen the instant power is applied. No
    circuit in the world can protect for every situation.

    > A, something will short out and PS will smoke.
    > or
    > B, something will short out and PS will turn off. In which case, after
    > dealing with whatever caused the short, the power supply will come to
    > life and work just fine.


    Or option C, the power supply has a safety diode, in the event
    something is wired up reverse, the diode blows before anything else
    does.

    > Oh really? Why don't you try it then. Force a cheap power supply on
    > and let it run for a while without a load. See what happens.


    Not a damn thing is going to happen. Do you know why? Because the power
    supply is a glorified step down transformer, ac/dc converter and
    partial noise filter, nothing more, nothing less. No "load" damage to
    speak of. If this nonsense were true, people plugging in nintendos,
    ataris, etc, (coleco anyone?) would have torched their PSU a long time
    ago. :)


    Power supplies do not increase current, they do not have final output
    transistors, they do not get signal reflection.. IE: a no load
    condition is not going to hurt them in the least bit.

    Want to run it for awhile with no load to see for yourself? (Btw, the
    power supply has a cooling fan, so it's already got a load on power
    up...) Take a paperclip, find the thin purple wire, short it against
    one of the black wires (doesn't really matter which, they're all
    ground, all goto the same place in the PSU too), and it'll power up and
    remain on so long as the paperclip is in place.

    You can even take voltage readings from the psu unit in this state,
    without any worry that you risk harming the rest of the computer in the
    event the psu is unstable.

    > Again...oh really? Take a high current amplifier, give it an audio
    > feed, disconnect anything that will create a load on the outputs, crank
    > the levels, and see what happens.


    This isn't the same. You get signal reflection, the load is necessary
    to absorb most of it. A power supply doesn't have any signal
    reflection, it's not amplifying anything. It's taking 120volts AC,
    converting it to 12+, 5+, 7.5+, 12-, 5- volts dc current..

    Your confusing a power supply with a radio transmitter..
     
    , Sep 2, 2006
    #43
  4. .

    Guest

    David Matthew Wood wrote:

    > Um.... no. Many years ago, I overestimated the space between the bottom
    > of a hard drive and the metal frame of the case. Turned machine on,
    > drive control board shorted and smoked. Because of this short, power
    > supply also smoked. How is that an assumption exactly?


    That doesn't mean the power supply had no protection, it means you
    managed to short out the 12 volt and 5volt rails.. Very stupid on your
    part.

    > And again later, I unknowingly had a bad power connector which turned
    > out to be shorted. Fired up the supply, it came on for not even half a


    I suspect if you had shorted both rails as you did previously, said
    power supply might have died a horrible death. It depends on it's
    internal design, of course.

    > second, and turned itself off again. Short was cleared, power was fired
    > up again, and all was well.


    Did you get an amp reading? If not, you can't be sure the power supply
    was okay. You also can't be sure the initial short didn't cause some
    components to become weak, and shorten the life of the power supply.


    > I had one smoke due to this.


    One rail, probably not, both rails to ground (which ehh, is what you
    obviously did) might/can kill a power supply.

    > Yes, and the better designed supplies shut down before this happens -
    > just as the better designs shut off in time to save themselves if they
    > are shorted.


    Not always. :)


    > Then why do the manufacturers of these very supplies advise against this?


    Do you have a url for a psu manufacturer who advises against running
    them with no load? (note this isn't actually possible, the psu itself
    places a load on some of it's own components, so really it is under
    load the entire time..)

    > high power, it will eventually kill the amp - if it doesn't trip the
    > protection circuits first!


    An amp isn't the same as a psu in your computer. Your amp is taking a
    small electrical signal and boosting it, possibly cleaning it up, and
    sending it on thru. Your power supply isn't boosting anything, it's
    reducing and converting, and if it's a really good one, doing some
    fairly nice square wave filtering.

    > Well since you seem to know more than the people who made these amps,
    > all of whom say NEVER run an amp without a load...


    A linear amplifier, shouldn't be run without a load, you will hurt it,
    The SWR will blow the finals.. A stereo amplifier isn't the same idea.
    I had big amps in the 80s when I was growing up, big stereo amps, from
    the old school stereo systems. Didn't hurt them a bit to fire it up
    with no speakers attached. I've got two peaveys here that don't mind
    either. :)

    > And while these speakers are being over driven, you are still driving
    > them and thus the amp is seeing a load! How long after completely
    > melting the speaker coils, have you run this amp exactly? How long have
    > you let it run under constant high power without a load? Do you
    > actually test this by turning the volume up higher and higher AFTER you
    > manage to blow the speakers?


    You do realize, unless you have a load on the amp, nothing is using any
    amplified signal right? Your not transmitting via an antenna, Your
    amplifyer isn't actually having to work unless/until a speaker is
    connected, regardless of your volume setting.

    I've blown several sets of car speakers using car amps, household amps,
    etc etc etc, left one running all night when I passed out once. :) I
    awoke to burned up speakers, but the amp was perfectly fine, connected
    new speakers, walla, tunes blaring again.

    A stereo amplifier isn't the same as a radio amplifier, such as a
    linear for ham/cb rig. The reason those will blow is due to the SWR,
    it's a signal reflection from the finals, Without a load (dummy load or
    antenna) the RF energy comes back to the finals, toasting them in the
    process. A car/home/house/guitar amp doesn't work like this.
     
    , Sep 2, 2006
    #44
  5. .

    Guest

    Rod Speed wrote:

    > There are no 'output transformers'


    Output transistors :) They do the real work inside the amp.. hehe.

    > There are no 'output transformers'


    Maybe he's talking about the little coil that sorta looks like a small
    transformer? :)
    (it's only purpose is to keep the signal cleaner.. heh)

    You know, if the guy was talking about an amplifier for a radio
    transmitter, he'd be right in the sense it shouldn't be run without a
    load, but an audio amplifier doesn't generate RF....
     
    , Sep 2, 2006
    #45
  6. .

    Guest

    Rod Speed wrote:

    > Basically because its cheaper to design it
    > so that it needs some load to start properly.


    Aye.. It is cheaper. It saves them a few capacitors... Hence the need
    for a load; You'd think they'd settle for the cooling fan.. but ah
    well.

    > And those care least about no speakers anyway.


    Tube amps are extremely forgiving as compared to the transistorized
    brothers.

    Tube amps is a really bad example for claiming no load kills them. They
    are hard to kill... very hard. He was better off trying to claim
    transistorized amps would die without a load.. It was more belivable.
     
    , Sep 2, 2006
    #46
  7. .

    Guest

    Plato wrote:
    > Lookout wrote:
    > >
    > > If all you hook up to the power supply is the MOBO (no RAM or CPU) and
    > > you can't even get to post (a beep, no beeps at all) then your problem
    > > is probably (98%) a fried MOBO. Just hope it didn't go any further.

    >
    > There are generally two things that cause a major smell when they burn
    > out:
    >
    > 1. Monitor
    > 2. The Case Power Supply


    You forgot two.. off the top of my head. A lightning striked NIC card
    and modem, god awful smell. :)
     
    , Sep 2, 2006
    #47
  8. .

    Rod Speed Guest

    wrote
    > Rod Speed wrote


    >> Basically because its cheaper to design it
    >> so that it needs some load to start properly.


    > Aye.. It is cheaper. It saves them a few capacitors...


    There's more involved than a few capacitors.

    > Hence the need for a load; You'd think they'd
    > settle for the cooling fan.. but ah well.


    There isnt really a lot of point designing to start with no load
    because if its not plugged in, there is no power on signal either.

    >> And those care least about no speakers anyway.


    > Tube amps are extremely forgiving as compared to the transistorized brothers.


    Yep, he hasnt actually got a clue about amps, or power supplys either.

    > Tube amps is a really bad example for claiming
    > no load kills them. They are hard to kill... very hard.


    And they dont get killed running with no load.

    > He was better off trying to claim transistorized amps
    > would die without a load.. It was more belivable.


    Yeah, he appeared to paint himself into a corner with the
    stupid claim about transformers and hasnt got the balls to
    admit that stupidity, or he doesnt actually have a clue about
    amps except that he does realise that tube amps exist.
     
    Rod Speed, Sep 2, 2006
    #48
  9. .

    Guest

    wrote:

    >
    > wrote:
    >
    >> It lasted about three weeks, or the first power fluctuation - Lost the
    >> power supply and mother board.


    >And while your forking out the hard earned cash on a good PSU, get a
    >good UPS as well. What's the point of a nice PSU if you have dirty
    >power coming into it? :(


    Well, I left out the good part...

    I had it connected to a backup-UPS 600 (on it's third set of
    batteries). And one reason I bought such a cheap setup is I was
    counting on the UPS to protect the darn thing.

    When the fluctuation hit the UPS scream'd and the PC died never to
    start again, it was at that point I figured the UPS system was no
    longer working :)

    I still use the UPS, but as an extension cord, the red power light is
    now flashing every few seconds, might loose that ability soon.


    --

    http://www.eglobe1.com/index.php/2006/09/02/unbelievable-pictures/
     
    , Sep 2, 2006
    #49
  10. .

    Guest

    wrote:

    > Some power supplies shut down when the voltage request goes too high;


    What's a "voltage request"?

    > IE: ground out condition, sure.


    Isn't that a current request?
     
    , Sep 2, 2006
    #50
  11. .

    Guest

    wrote:
    > wrote:
    >
    > > Some power supplies shut down when the voltage request goes too high;

    >
    > What's a "voltage request"?


    Shrug, I likely misworded what I meant, sorry...

    > > IE: ground out condition, sure.

    >
    > Isn't that a current request?


    Yes, but with that condition, the resistance level goes thru the roof;
    You basically turn the power supply's connections into a heating
    element. :(
     
    , Sep 3, 2006
    #51
  12. .

    Guest

    wrote:
    > wrote:


    > > > Some power supplies shut down when the voltage request goes too high;

    > >
    > > What's a "voltage request"?

    >
    > Shrug, I likely misworded what I meant, sorry...
    >
    > > > IE: ground out condition, sure.

    > >
    > > Isn't that a current request?

    >
    > Yes, but with that condition, the resistance level goes thru the roof;


    Millions and millions of ohms?

    > You basically turn the power supply's connections into a heating
    > element. :(


    How hot does a PC power connector with megaohms of resistance get?
     
    , Sep 3, 2006
    #52
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