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PC powers on for 2-3s then shuts off? How to troubleshoot?

Home built machine thats been running fine for 4-5 years. Turn it on and it powers up for 2-3s (i.e. lights, fan) then turns off. After that it's dead until I unplug and re-plug in the power supply.

What is the best way to troubleshoot this?

It could be any of the following but where do I start?
6 answers Last reply Best Answer
More about powers shuts troubleshoot
  1. Does it eventually start up if you keep trying? That's a classic sign of a dying PSU. Sort of like a car that cranks and cranks before finally turning over. Generating startup power is usually the highest strain on a PSU's power output.
  2. TMTOWTSAC said:
    Does it eventually start up if you keep trying? That's a classic sign of a dying PSU. Sort of like a car that cranks and cranks before finally turning over. Generating startup power is usually the highest strain on a PSU's power output.



    So is the process just to start with the PSU, replace it then on to next thing? What would that be? How does one troubleshoot Memory/CPU/MOBO? Only way I can think is just by replacing each as you go.
  3. Best answer
    Skip to the end for useful advice, the rest is more philosophical rambling on the art of computer diagnostics.

    A lot of us here have piles of old parts lying around so swapping in known good components isn't a problem. We usually point out the most likely culprits, the simplest to test, then the least expensive and keep moving down the list to save time and money. Without having access to spares, you can still test things but it's more complicated.

    Let's say the PSU is flaky, sometimes it starts and sometimes it doesn't. But you don't know that so you try checking the RAM. You go from 2 sticks to 1 stick, you try it in every slot, then repeat with the other stick. Voila, it finally boots. You shut it off and try again no problems. So you think you've identified a bad RAM stick and slot, but in reality the half dozen boot attempts warmed up the PSU enough to get going. Then you shut it off and the next day it won't turn on.

    There's a slew of diagnostic methods for each component, but each can give false positives if the problem is somewhere else. A CPU might overheat because the cooler is at fault, or because the mobo voltage regulation is screwy. You shove a beefy watercooler in and get the temps down, but it's still getting overvoltage and fries itself after a month.

    Anyway, you said it's dead until you unplug and plug it back in. Does that mean it starts up ok afterwards? Or that it just tries again for 2-3 seconds then dead? If it does eventually start, it points towards a PSU because they can go bad slowly. Other types of component failures are more binary, they work or they don't. That's not always the case but it's a process of elimination.
  4. TMTOWTSAC said:
    Skip to the end for useful advice, the rest is more philosophical rambling on the art of computer diagnostics.

    A lot of us here have piles of old parts lying around so swapping in known good components isn't a problem. We usually point out the most likely culprits, the simplest to test, then the least expensive and keep moving down the list to save time and money. Without having access to spares, you can still test things but it's more complicated.

    Let's say the PSU is flaky, sometimes it starts and sometimes it doesn't. But you don't know that so you try checking the RAM. You go from 2 sticks to 1 stick, you try it in every slot, then repeat with the other stick. Voila, it finally boots. You shut it off and try again no problems. So you think you've identified a bad RAM stick and slot, but in reality the half dozen boot attempts warmed up the PSU enough to get going. Then you shut it off and the next day it won't turn on.

    There's a slew of diagnostic methods for each component, but each can give false positives if the problem is somewhere else. A CPU might overheat because the cooler is at fault, or because the mobo voltage regulation is screwy. You shove a beefy watercooler in and get the temps down, but it's still getting overvoltage and fries itself after a month.

    Anyway, you said it's dead until you unplug and plug it back in. Does that mean it starts up ok afterwards? Or that it just tries again for 2-3 seconds then dead? If it does eventually start, it points towards a PSU because they can go bad slowly. Other types of component failures are more binary, they work or they don't. That's not always the case but it's a process of elimination.


    "Does that mean it starts up ok afterwards? Or that it just tries again for 2-3 seconds then dead?"

    After re-plugging in it tries again for 2-3s and then just dies.
  5. Ok, still going to focus on the PSU for now. Try unplugging it, then pressing and holding the power switch for 10 seconds. That should fully discharge any residual power. Then plug it back in and try booting again.
  6. TMTOWTSAC said:
    Skip to the end for useful advice, the rest is more philosophical rambling on the art of computer diagnostics.

    A lot of us here have piles of old parts lying around so swapping in known good components isn't a problem. We usually point out the most likely culprits, the simplest to test, then the least expensive and keep moving down the list to save time and money. Without having access to spares, you can still test things but it's more complicated.

    Let's say the PSU is flaky, sometimes it starts and sometimes it doesn't. But you don't know that so you try checking the RAM. You go from 2 sticks to 1 stick, you try it in every slot, then repeat with the other stick. Voila, it finally boots. You shut it off and try again no problems. So you think you've identified a bad RAM stick and slot, but in reality the half dozen boot attempts warmed up the PSU enough to get going. Then you shut it off and the next day it won't turn on.

    There's a slew of diagnostic methods for each component, but each can give false positives if the problem is somewhere else. A CPU might overheat because the cooler is at fault, or because the mobo voltage regulation is screwy. You shove a beefy watercooler in and get the temps down, but it's still getting overvoltage and fries itself after a month.

    Anyway, you said it's dead until you unplug and plug it back in. Does that mean it starts up ok afterwards? Or that it just tries again for 2-3 seconds then dead? If it does eventually start, it points towards a PSU because they can go bad slowly. Other types of component failures are more binary, they work or they don't. That's not always the case but it's a process of elimination.


    Two new PSU's installed and no go. Same thing. I think something is fried. Looks like time for an upgrade.
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