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Computer won't turn on (PSU problem?)

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#1 RB_Kandy


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Posted 14 June 2011 - 09:01 AM

Computer won't turn on (PSU problem?)

So my friend got a broken computer from her sister, it's a 4 year old gaming comp from Dell.
The original problem was it wouldn't boot because of a "Unmountable_boot_volume" error.

Now we got a new problem, after tinkering with the bios (disabling drive2 and re-enabling drive2, getting same error message), we turned the computer off. An hour later, giving it a second try, the power button is pressed and... nothing!!!
No image on monitor, no CPU fan, no hard drive sound, no PSU fan start up, power button on computer case does not light up. The power plug was unplugged on both ends, plugged back in good and tight, and... nothing!

The only sign of life is a little green light on the motherboard that turns on when the electrical cable is plugged into the wall. It goes out after about 10 to 20 seconds after it is unplugged. I'm not sure what this light is, some kind of a capacitor-is-ready light?

Anyhow, I'm wondering, is this caused by a bad PSU, or is it possible we really messed something up on the bios just by enabling and disabling drives from the menu?

Any ideas on what to do? Is it possible doing that thing where you change the jumpers around to reset cmos would fix the problem?

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#2 keyboardNinja


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Posted 14 June 2011 - 04:10 PM

If the light on the motherboard is lit when the power cord is plugged in, that should indicate that that PSU is working.

It's likely the motherboard itself that is borked. I doubt you messed up the BIOS settings just by enabling/disabling drives.
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#3 RB_Kandy

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Posted 14 June 2011 - 04:40 PM

My plan to help her out tomorrow is this:

1. Find new power cable to go from wall outlet to PSU, then start computer.
2. Unplug all external devices (mouse, keyboard, monitor), then turn on computer.
3. Remove case power button from mobo, touch pins together with flat head screwdriver to try to start computer.
4. Remove cmos battery, put cmos battery back in, turn on computer.
5. Disconnecting all drives, all PCI/PCIe cards, all case fans, all external devices (leaving only the CPU fan plugged in). Then start computer while seeing if CPU fan turns.
6. Same as above with RAM sticks removed.
7. Remove PSU from case, disconnect all plugs from PSU, test PSU with a multimeter/voltage meter (will google for instructions). If multimeter is not available place paperclip on the green and black wire of the atx plug with having a case fan plugging in the psu and flipping the power on to see if the fan spins.
8. If the steps 1 through 6 fail to start the computer, and step 7 turns on the case fan plugged into the PSU, than diagnose the problem as mobo failure, salvage drives and nVidia video card from the comp, and move on to a new comp. If PSU doesn't activate fan, diagnose the problem as dead PSU.

Does anyone have any other steps they might recommend, or critiques of those steps? And any idea on how much of a shock or what bad result might happen if she screws up testing the PSU with voltage meter or paperclip? I mean, if this could give her a seriously painful shock or cause a fire, I won't have her test the PSU, I'll just go with my intuition that it's the mobo.
Also, the pins on the mobo for the power button, could touching together the wrong 2 pins (power button pins) with the screw driver mess something up?

Edited by RB_Kandy, 14 June 2011 - 04:42 PM.

#4 Rick Adams

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Posted 14 June 2011 - 05:10 PM

My 2 cents:

I would definitely try resetting the bios using the jumpers before declaring the motherboard dead (or removing any components). If that didn't work I would probably even go so far as to remove the mobo from the case completely and bench test it connecting just the power supply and the monitor, to rule out any shorting that might be occurring inside the case (I've seen it before). Of course when working with these electronic components you should always make sure you're properly grounded to avoid static damaging components.

Good Luck!

#5 hamluis



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Posted 15 June 2011 - 09:20 AM

Rather that reset the CMOS...I would replace the CMOS battery, if this is a desktop.


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