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Computer won't turn on after power outage


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#1 Kinetic

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Posted 13 July 2013 - 09:22 PM

Hi everyone,
 
I had a power outage yesterday and my ~10 year old HP Pavillion 504n doesn't turn on anymore. 
 
- When I press the power button, nothing happens. Fan doesn't turn, absolutely no response from the PC. 
- The power light at the back remain green (it doesn't flashes) so I assume it's not the PSU fault?
- The computer was in Sleep mode when the power went out.
- PC is plugged into an extension cord which I *think* has a surge protector* but i'm not sure
- When I plug the PC into the wall outlet, the fan turns a few rotations and then stops. 
 
Is it the PSU fried or the motherboard? Someone suggested I should try replacing the PSU but would any PSU work? As long as it has the right power connector and it fits the case?
 
Thanks!

Edited by Kinetic, 13 July 2013 - 09:34 PM.


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#2 JHMcG

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Posted 13 July 2013 - 10:34 PM

You could try clearing the bios and see if that helps. We had a power outage where I live a few days ago, and my machine would not restart after the power came back on, but in my case it was because I use an "Uninterrupted Power Supply" which was causing the problem. Had to shut it off and then restart it in order for my computer to work.

 

Since your machine was in "Sleep Mode" when the power went off, that might be causing a problem, that possibly clearing the bios might solve.


Edited by JHMcG, 13 July 2013 - 10:36 PM.


#3 slgrieb

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Posted 13 July 2013 - 10:34 PM

The power supply is almost certainly fried. It's also possible the motherboard is also blown. Systems as old as yours didn't include the same level of protection against power surges, low voltage conditions, etc. as newer boards. My advice is to take it to a shop and have the rig tested. You could buy a new power supply,  but even then, both the mainboard and/or  the CPU might be toasted as well. Without some advanced diagnostic tools such as a POST card, you can't be sure about what's going on with the system. In this situation, you are probably better off with some professional assistance, both in terms of money and downtime.


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#4 Kinetic

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Posted 13 July 2013 - 11:46 PM

You could try clearing the bios and see if that helps. We had a power outage where I live a few days ago, and my machine would not restart after the power came back on, but in my case it was because I use an "Uninterrupted Power Supply" which was causing the problem. Had to shut it off and then restart it in order for my computer to work.

 

Since your machine was in "Sleep Mode" when the power went off, that might be causing a problem, that possibly clearing the bios might solve.

 

I can't get into BIOS because the PC doesn't even power on :(

 

 

The power supply is almost certainly fried. It's also possible the motherboard is also blown. Systems as old as yours didn't include the same level of protection against power surges, low voltage conditions, etc. as newer boards. My advice is to take it to a shop and have the rig tested. You could buy a new power supply,  but even then, both the mainboard and/or  the CPU might be toasted as well. Without some advanced diagnostic tools such as a POST card, you can't be sure about what's going on with the system. In this situation, you are probably better off with some professional assistance, both in terms of money and downtime.

 

Thanks for the advice :)



#5 slgrieb

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Posted 14 July 2013 - 12:16 AM

You are certainly welcome to the advice, and I wish I could be more helpful. You can only do so much with online support, and I think you have a dead computer. The good news is that you can probably transfer your data without much effort even if it isn't backed up. Still, get the system checked by a trusted pro. Given current hardware prices,  I just wouldn't sink much money into the computer. Car repair, home repair, computer repair; it's easy to find yourself upside down.


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#6 JHMcG

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Posted 14 July 2013 - 07:35 AM

Re clearing the bios, you don't have to turn on the machine. What you do is unplug it, then take the mobo battery out of its socket, and look for two terminals labled "clr cmos" and short them together for a few seconds. If you can't find two terminals labled "clr cmos" then briefly short the positive and negative terminals in the mobo battery socket. This is to clear any "Capacitance" so as to leave the bios completely devoid of power so it will go to its default settings.

 

Once that is done, reinstall the mobo battery, then plug the machine back in and see if it works. Doesn't cost anything, and doesn't take long to do, so it's worth a try.



#7 Kinetic

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Posted 14 July 2013 - 11:37 AM

Re clearing the bios, you don't have to turn on the machine. What you do is unplug it, then take the mobo battery out of its socket, and look for two terminals labled "clr cmos" and short them together for a few seconds. If you can't find two terminals labled "clr cmos" then briefly short the positive and negative terminals in the mobo battery socket. This is to clear any "Capacitance" so as to leave the bios completely devoid of power so it will go to its default settings.

 

Once that is done, reinstall the mobo battery, then plug the machine back in and see if it works. Doesn't cost anything, and doesn't take long to do, so it's worth a try.

 

By "short", do you mean release any charges by touching them to the ground? Or to another conductive material?



#8 JHMcG

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Posted 14 July 2013 - 11:52 AM

Just connect the two battery terminals to each other for a few seconds with no battery installed. That will cause any capacitance to drain. Easiest way to do it is with a screwdriver touching both terminals at once.


Edited by JHMcG, 14 July 2013 - 11:54 AM.


#9 dc3

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Posted 14 July 2013 - 04:01 PM

There should be a jumper next to the CMOS battery with a three pin header.  To clear the CMOS the center pin will always be covered by the two pin connector, remove the connector and place it so that it covers the normally vacant pin.

 

There is another way to determine if this is a PSU or a motherboard issue.

 

The purpose of this procedure is to bypass the motherboard to test the PSU.
 
When a computer begins the boot process the motherboard initiates the start up of the PSU. Because of this it is difficult to determine whether the problem is with the motherboard or the PSU when a computer shows no signs of starting up. The purpose of the procedure is to determine if the problem is with the motherboard or the PSU.  For safety purposes please follow the instructions step by step.
 
This test is for ATX PSUs. Some manufacturers use non-ATX PSUs with 20/24 pin connectors that do not have the same pinout as a ATX PSU.
 
First, shutdown your computer. Then unplug the power cable going into your computer.
 
Once you have opened the case, touch the metal of the case to discharge any static electricity.  
 
The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle.  To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard.  Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed.  This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.
 
th_main24index.jpg
 
From the top left to right the pins are 13-24, the bottom from left to right are 1-12.
 
  
Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14.  If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner.  This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom.  The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper.  For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation.  It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing.  You are at risk of electrical shock if you are holding the jumper when you power up the PSU.  Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.
 
Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on.  I would suggest that you not  leave this connected any longer than is necessary for safety purposes.
 
To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.

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#10 JHMcG

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Posted 14 July 2013 - 04:54 PM

Re the "Clear Cmos" terminals with a jumper on them , that is true in some cases, BUT :

1) Some mobos have two terminals without a jumper on them

2) Some mobos don't have "Terminals" but rather just two "Solder Points" that have to be shorted to clear the CMOS

3) Some mobos don't have any bios clearing contacts, and you have to short the "Battery Terminals" with the battery removed, and the machine powered down.






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