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New working system build not starting after USB device connected to system (but system had no power connection)

Last response: in Motherboards
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April 29, 2014 6:30:04 PM

Hello - I have searched the forums prior to this, but if there is already an answer to this, please feel free to point me in that direction. I appreciate any and all help in advance. Thank you.

My basic question is:
What can a USB connected device do to a machine that is not plugged in itself (e.g. PSU is not plugged into wall), but itself sparks when connecting to it's own local power?

My more complicated question is:
What could have gone wrong here and what can I salvage to get this system up and running?

Situation:

    I had assembled an entire system (specs provided below), including all components, an OS (windows 8.1), and related drivers. Everything was working on the system (all drives, network, sound, video, etc.)
    I unplugged the system to open the case to see if I could fit a PCIE card I had on another machine - a visual inspection confirmed that I could not (e.g. I did not try to plug it in)
    I got the system ready to start up again
    I kept the system unplugged, but started plugging in USB peripherals prior to start up.
    I connected an external HD via a USB 2.0 connection available on the motherboard.
    I then plugged the power (12v) into the back of the HD...
    I observed a small spark at the touch point of the connection between the 12v AC adapter plug and the HD - no smell, no "pop" sound. There was just a spark, which was from the side of the adapter touching the metal casing (see note below about external HD)
    I continued to plug in HD (only sparked once)
    I plugged in power to system (power to PSU)
    I attempted to power up the system and nothing happened. No fan start-up, no beeps, no lights on the power button, nothing.


Things I have (and have not) checked:

    I have lamp tested the outlet - the socket is fine
    I have tested the power cord (from wall to PSU) - the cord is fine
    I have paperclip tested the PSU - the PSU did not pass the test(s) - with added load of a DVD drive and separate test against the motherboard with only CPU and HSF.
    I have visually inspected the motherboard - there is nothing that appears either burnt, degraded, or changed. It looks fine.
    I have tested the external HD against my laptop (while praying) and the laptop recognized the drive and was able to read and process files on the drive.
    I have not tested the motherboard with any other meters, or testing equipment


The system:

    Motherboard - ASROCK|FM2A88X-ITX+ R
    PSU (Allied SL-8250SFX) included within Apex Case MI-008)
    CPU - AMD|TA4-5300 3.4G 1M FM2 R
    External HD - WD My Book Studio 2TB - note this thing has a metal housing which is what I am sure created the short between the side of the power supply and the case itself (of the external hard drive)
a c 160 V Motherboard
April 29, 2014 6:43:58 PM

I bet the PSU died. That is the first thing I would check out. If you have a volt meter, see what the voltages are.
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April 29, 2014 6:51:11 PM

spooky2th said:
I bet the PSU died. That is the first thing I would check out. If you have a volt meter, see what the voltages are.


Thanks - I am thinking that is what it is... but I thought I would throw it out there to see if I missed anything. I hope I can RMA it as the unit is only like 1 day old and I don't think that I was using it abnormally.

out of curiosity - how often do PSUs fail? Is it rare or common?
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a c 160 V Motherboard
April 29, 2014 6:59:00 PM

You can look at the reviews of just about any PSU and there are always some dead on delivery and some die real soon within days or a month or two.
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Best solution

a b V Motherboard
April 29, 2014 9:55:45 PM

You got a cheapo PSU.

That's why it crapped out on you.

A PSU can kill your entire computer, so you need to treat the PSU with the same respect you would a CPU or GPU, spend money and buy a quality one.

PSUs can hold power even when unplugged from the wall, to disperse any built up power, press the power button on the case after unplugging the PSU, your fans will spin for about a second and then there won't be any power in your computer and it will be safe to go touching the stuff inside it.
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April 30, 2014 7:21:28 AM

James Mason said:
You got a cheapo PSU.

That's why it crapped out on you.

A PSU can kill your entire computer, so you need to treat the PSU with the same respect you would a CPU or GPU, spend money and buy a quality one.

PSUs can hold power even when unplugged from the wall, to disperse any built up power, press the power button on the case after unplugging the PSU, your fans will spin for about a second and then there won't be any power in your computer and it will be safe to go touching the stuff inside it.


Thanks - I had a suspicion that my "value buy" may have been part of the reason for the failure. Are there any ITX PSU brands that you would recommend? I appreciate any pointers. I have built several boxes from the graveyard of perviously working machines, but this is the first one wherein I have the option to chose all the components.
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a b V Motherboard
April 30, 2014 12:48:46 PM

Choose a PSU from Seasonic or XFX that meets your wattage requirements. It appears the case actually accepts regular fullsize atx PSUs.

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April 30, 2014 5:11:10 PM

James Mason said:
Choose a PSU from Seasonic or XFX that meets your wattage requirements. It appears the case actually accepts regular fullsize atx PSUs.



Thanks for the suggestion.
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May 4, 2014 7:19:27 PM

James Mason said:
Choose a PSU from Seasonic or XFX that meets your wattage requirements. It appears the case actually accepts regular fullsize atx PSUs.



Thanks again. After replacing the PSU and rebooting the system the following is happening:

    - all fans turn on
    - I am getting 5 beeps
    - the HD spins and the DVD drive runs
    - no video is showing up (I have used both HDMI and VGA connections


Because 5 beeps is a "VGA error" for the ASROCK UEFI BIOS, I know that it is a graphics problem based on the beeps, and I have reseated the CPU (and checked for bent pins), as well as reseated all RAM, etc.

My Question is if the 5 beep code refers to a video error and I am using an AMD chip with (see above) with integrated Radeon graphics, should I RMA the motherboard or the CPU?

My guess is based on the original problem, it's the motherboard, but I wanted to check with more seasoned minds than mine.
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a c 160 V Motherboard
May 4, 2014 8:31:09 PM

Looks like the PSU was not the only thing damaged. The only way I can think of, is to install another CPU and see what happens.
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