Question Desktop PC wont power up. Totally dead. Help, please?

Mar 28, 2019
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I recently inherited an Acer desktop pc, which had not been used for about 2 years. Yesterday I hooked it up and set about doing years worth of Windows updates which took hours and hours. Eventually, after all the updates were done, I browsed around for half an hour then I shut it down. But then when I came to switch it on today, it was dead. No noise. No lights. Nothing.

I tried changing the fuse, tried using a different plug socket, tried an alternate power cable, but still it was dead. I then opened up the tower and it was absolutely full of dust. I gave it a good clean and even switched out the cmos battery for a new one, after reading online that that could be the issue. Still nothing. Even plugging it in with the side panel off, I could see the motherboard wasn't lit up or doing anything at all. There's just no power getting to anything, it would seem.

So I'm at a dead end now (no pun intended). I'm not really too informed beyond the basics when it comes to computers, so I've done all I can now short of taking it into a repair shop and paying for whatever they come up with.

Does anybody have any ideas what may be wrong? Or any additional things I can try and do myself?

Any and all suggestions very much appreciated.

Thanks.
 
Mar 28, 2019
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You can test the power supply independently. Unplug all the cables from the computer.

If your PSU has a 24-pin connector you simply short pins 15 (Black) and 16 (Green) with any small piece of wire, paperclip, etc.

https://en.wikipedia.org/wiki/ATX

If it is non-standard, well, you are going to have to provide the exact model of desktop.
Yeah it's 24 pins, if' I'm looking at the right one now. They're mixed colours though of pink, yellow, black, green purple, white... etc. Do you just yank that fitting out or is there a little catch to unlock it? Never messed with these fittings before.
 

Eximo

Titan
Herald
There is a small tab on one side that needs to be depressed as you pull. That is true of all connectors of that style.

Green is the one we are interested in. That is the pin that the power switch on the front of the computer shorts to ground to tell the power supply to turn on. Once it is disconnected and you either prove that it turns on on its own, or not, you are one step closer to knowing what is wrong.

In the case the power supply doesn't turn on it, it is dead and needs replaced. If it does turn on, that means some other piece of hardware in the system has failed, badly, and has an internal short. The power supply will not start if it detects a problem like that. (Prevents fires)
 
Mar 28, 2019
7
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10
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There is a small tab on one side that needs to be depressed as you pull. That is true of all connectors of that style.

Green is the one we are interested in. That is the pin that the power switch on the front of the computer shorts to ground to tell the power supply to turn on. Once it is disconnected and you either prove that it turns on on its own, or not, you are one step closer to knowing what is wrong.

In the case the power supply doesn't turn on it, it is dead and needs replaced. If it does turn on, that means some other piece of hardware in the system has failed, badly, and has an internal short. The power supply will not start if it detects a problem like that. (Prevents fires)
Thanks. I got the 24 pin plug out in the end.

I put the paper clip in the green and the black pin next to it. When I switched it on there was only a very quiet, low, strange screeching noise when i got VERY close that I could hear. I dont really know what it would do if it was working, but that's all I got out of it.

Should it be much louder and a fan come on as well??
 

Eximo

Titan
Herald
High pitched noises are typical of all switch mode power supplies. That is usually the switching frequency you are hearing or a sympathetic noise from the capacitors or coils. Though many newer power supplies do have a passive cooling mode so running silent isn't all that strange. Not something I would expect to see in an OEM though.

You can try plugging a fan into or something. A volt meter would come in handy as well.

No power LEDs on or inside the power supply?
 
Mar 28, 2019
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High pitched noises are typical of all switch mode power supplies. That is usually the switching frequency you are hearing or a sympathetic noise from the capacitors or coils. Though many newer power supplies do have a passive cooling mode so running silent isn't all that strange. Not something I would expect to see in an OEM though.

You can try plugging a fan into or something. A volt meter would come in handy as well.

No power LEDs on or inside the power supply?
Yeah, it sounds like a frequency type of noise. That's it.

Don't really have a fan or a volt meter. Would any other household item work?

The power supply unit has a solid metal case around it so, can't see a lot. The vent it does have I cant see any lights inside though. There are no lights showing on the motherboard or anywhere if I plug the unit into the wall whilst still connected to everything. So no real signs of life anywhere that I can see.
 

Eximo

Titan
Herald
Well if you happened to have some old 6v (for the 5V) or 12v (For the 12V) bulbs you could wire them up to the PSU. That would only prove that it is producing power through.

The computer has fans I hope? Those run on 12V and most will at least spin with 5V applied.

I wouldn't risk anything else if you don't know if the power supply is good. The idea is to isolate it from the computer so that you know there isn't a faulty component in there.

Only other approach would be to try the system with the bare minimum hardware. CPU, Motherboard, and one memory stick. Everything else unplugged but the 24pin ATX and the 4-pin CPU power.

If it doesn't work at that point, it is either the power supply or one of those three components.

After that, you need some known good hardware to test further. Which is what computer shops will often have.
 
Mar 28, 2019
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Well if you happened to have some old 6v (for the 5V) or 12v (For the 12V) bulbs you could wire them up to the PSU. That would only prove that it is producing power through.

The computer has fans I hope? Those run on 12V and most will at least spin with 5V applied.

I wouldn't risk anything else if you don't know if the power supply is good. The idea is to isolate it from the computer so that you know there isn't a faulty component in there.

Only other approach would be to try the system with the bare minimum hardware. CPU, Motherboard, and one memory stick. Everything else unplugged but the 24pin ATX and the 4-pin CPU power.

If it doesn't work at that point, it is either the power supply or one of those three components.

After that, you need some known good hardware to test further. Which is what computer shops will often have.
Yeah, there's a small fan. It's plugged into the motherboard. If I unplug it, how do I connect it to the power supply to test it?
 

Eximo

Titan
Herald
You would want to use that ATX diagram from above. Find the 12V+ and a nearby ground. The first two wires on the fan header should be 12V+ and GND. They may be color coded Red and Black. The third wire will be RPM sensor.

You will need some wires or you could use paperclips again.

This seems a little beyond your area of expertise. If you don't want to risk messing anything up maybe just try the removal of all non-critical parts first.

I suppose it would be up to you if you want to try buying a power supply and testing. Depends on your future plans with these components.

I am very limited in the advice I can give without the model of the computer. I am speaking in generalities and not specific things related to your hardware.
 
Mar 28, 2019
7
0
10
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You would want to use that ATX diagram from above. Find the 12V+ and a nearby ground. The first two wires on the fan header should be 12V+ and GND. They may be color coded Red and Black. The third wire will be RPM sensor.

You will need some wires or you could use paperclips again.

This seems a little beyond your area of expertise. If you don't want to risk messing anything up maybe just try the removal of all non-critical parts first.

I suppose it would be up to you if you want to try buying a power supply and testing. Depends on your future plans with these components.

I am very limited in the advice I can give without the model of the computer. I am speaking in generalities and not specific things related to your hardware.
Yeah, it's a little beyond me trying to connect all that up. I'll try the other idea instead.

So basically I unplug everything, except the big 24 pin plug? Is that right?
 

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