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  #1  
Old 01-11-2015
kaskuser kaskuser is offline
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Question Please help: Dead PC

I'm just an end-user, not a technician.

I was trying to reuse an abandoned AMD Sempron 3000+ desktop PC.
When the Power button was pressed, the PC was still off, even PSU's fan was off.

I had tried replacing the PSU with another one, replacing the system unit casing (just in case the Front Panel were damaged), but the PC was still off.

I had also tried turning on only the PSU (directly connected to the electric power source), but its fan was off too.

Is it the PSU, motherboard, or else, that is damaged and needs to be replaced?

Thanks in advance.
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Old 01-11-2015
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If a known working PSU won't start the PC up, then it's probably the motherboard.

By the way, what do you mean by "I had also tried turning on only the PSU (directly connected to the electric power source), but its fan was off too."? Did you try the paperclip start method (shorting the green wire to a black wire on the ATX connector)? An ATX power supply won't just turn on by itself when you connect it to the mains power.
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  #3  
Old 01-11-2015
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Quote:
Originally Posted by kaskuser View Post
When the Power button was pressed, the PC was still off, even PSU's fan was off.
Make sure the power button is properly connected to the correct two pins of the motherboard. Remember: The motherboard tells the PSU to turn on. There's no direct connection between the power button and the PSU.

Quote:
Originally Posted by kaskuser View Post
I had also tried turning on only the PSU (directly connected to the electric power source), but its fan was off too.
That won't do anything. The motherboard has to tell the PSU to turn on. If you are trying to power up a PSU by itself, you have to bridge the green wire with a ground wire to emulate the motherboard. This is what c_hegge is suggesting.

When all else fails, you should try just the motherboard, outside of the case with just the PSU and no other components to see if you can at least get power to the board.
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  #4  
Old 01-12-2015
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Quote:
Originally Posted by jonnyGURU View Post
That won't do anything. The motherboard has to tell the PSU to turn on. If you are trying to power up a PSU by itself, you have to bridge the green wire with a ground wire to emulate the motherboard. This is what c_hegge is suggesting.
Thanks jonnyGURU and c_hegge, many people suggested to me to do that but I didn't understand, until you guys mentioned that. BTW, will I be electrocuted when bridging the green wire with a ground wire while connecting the PSU to the A/C power source?
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Old 01-12-2015
Coornio Coornio is offline
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Quote:
Originally Posted by kaskuser View Post
Thanks jonnyGURU and c_hegge, many people suggested to me to do that but I didn't understand, until you guys mentioned that. BTW, will I be electrocuted when bridging the green wire with a ground wire while connecting the PSU to the A/C power source?
I don't know about that, but I reckon that if you wear protective gloves you won't be :P
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Old 01-12-2015
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No, you won't be electrocuted unless you open up the PSU and grab onto the AC side. So don't open the PSU - there are no "user-serviceable" parts inside anyway.

The output side of the PSU is at most +12VDC and not enough current to kill you (don't know what happens if you have an implanted heart pacemaker - so I would avoid that if that is the case).

FTR, I am not a fan of the paper clip method. For one, older PSUs may have been made before color coding became required. And for another reason, no load is put on the supply with the paper clip so all you know is that the PSU will turn on, not that it is outputting the correct voltages.

I recommend using one of these PSU Testers. They are safe, provide a small load, and these better testers also indicate the actual voltages - lesser models use LEDs to indicate the voltage is just within some "range".
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  #7  
Old 01-12-2015
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Thanks everyone, Digerati for the PSU Tester link.

I just tested both PSUs by wiring the green wire and black/ground wire, then connected them to the A/C electric power. Both PSUs were switched on. So I guess it's not the PSUs that are broken.

Could it be the motherboard?

How do I test whether a motherboard is healthy or damaged? Is there some device like the PSU Tester mentioned by Digerati?

Thanks again~ ^^
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Old 01-12-2015
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Quote:
How do I test whether a motherboard is healthy or damaged? Is there some device like the PSU Tester mentioned by Digerati?
I wish - but with 1000s of different motherboard out there, a simple plug in tester is not possible.

Unfortunately, there is no simple test that does not risk damaging mounted devices, like the CPU and RAM. You can take it to a shop and let them risk their spare CPU and RAM. Most shops have some laying around they can (reluctantly, no doubt) sacrifice.
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  #9  
Old 01-13-2015
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Thanks again Digerati ^^

Last edited by kaskuser; 01-14-2015 at 01:53 AM.
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