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So the computer was running fine until I decided to plugin a external drive via the usb. I didn't even get to insert it, as soon as the usb touched the usb port, the computer shut off and there was a weird loud crackling noise from the Power supply unit. I unplugged everything and back in, the loud crackling is back.

When I press power button, the computer momentarily starts then immediately shuts off. I press it again and same thing. with the regular loud tick sounds every 2 seconds.

how to fix this and what has happened or happening?

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Our crystal ball is murky. We will need more information on what is involved, and what you've tried already. Perhaps start by testing your power supply: How to test a power supply? – Ƭᴇcʜιᴇ007 Apr 15 '12 at 19:15
Note that the timing of the crash with the plugging in of the USB drive may or may not be significant -- it may be pure coincidence. But if the USB drive did it I suspect that the USB drive's power supply has a short and is applying "juice" to the USB shell. (Note that this could be a "life safety hazard" -- possible electrocution hazard.) – Daniel R Hicks Apr 15 '12 at 20:39
Is this a laptop or a desktop system? (In any event, the "tick" may be the power supply attempting to "come up" but encountering some sort of fault.) – Daniel R Hicks Apr 15 '12 at 21:12

The following is what comes to mind, especially if the system just hard powered off and did not give you a glimmer of the BSOD before doing so, or did NOT reboot:

  • You have some type of electrical short in the system. Perhaps something metallic, like a screw, is touching the motherboard.
  • Your USB ports, or the small PCB they exist on, are damaged.
  • The wires leading from the USB ports to the motherboard are damaged or short circuiting. This normally wouldn't "just happen" inside a PC unless the wires were in the way of a fan or something.
  • The USB header that connects the ports to the motherboard is not connected properly or is connected to the wrong motherboard pins.
  • Possibly your power supply is damaged, or some electrical component on the motherboard has suffered damage due to a power surge. I would suspect this last.

A short might have damaged your hard drive but it also could be the power supply making that noise.

If you are experienced with building computers I would open it up and take a look at it and see if any metal is touching the motherboard, and possibly check the above. If you lack this expertise get someone to help you.

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when i plugin the power, i can hear the PSU whirling and starting up with some tick noise (not a clicking fan noise but electrical sounding ticks). when I try power on, the led lights come on and computer shuts down after 1 second. when i press it again, the same thing. – pcnutz Apr 15 '12 at 19:35
Honestly at this point I'd unplug it and get a techie friend to physically look at it, you might be causing your system further damage. Start with trying a different PSU. – LawrenceC Apr 15 '12 at 19:36
it sounds like a crackling, with pop noises. nothing seems to be loose inside – pcnutz Apr 15 '12 at 19:59
If the PSU is making those noises, it could be a short with a spark jumping a gap. My first advice would be to pull your hard drive out and try a new PSU. – Rob Apr 15 '12 at 20:33

Loud tick sounds might be an indication that your hard drive (on the computer, not the USB hard drive) has crashed. If so, the computer would start, show some startup text and then fail to start.

On the other hand, that would probably not cause the computer to shut down. It would be more likely that it would supply an error message saying something about not being able to access the hard drive.

A diagnosis could be made by disabling the hard drive (in BIOS, or by physically remove/replace it) and see if the loud tick noises disappear when you start the computer

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the tick sounds appear as soon as the pc is plugged in and not powered on. – pcnutz Apr 15 '12 at 19:37

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