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PSU immediate shutdown troubleshooting help pls...


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#1 grindy

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Posted 20 December 2010 - 11:38 PM

Couple of days ago I'm rendering some video and begin to smell something strange. Since one of my neighbors sometimes burns some "unusual" stuff in his fireplace, I went outside to see if it was outside or inside (wasn't out there). By the time I got back in the smell was getting pretty strong. As I was shutting my system down (normally - thru Win7) it shut itself down completely before windows could do it.

When I opened the case the smell was fairly strong there. So, while it's cooling down I took the time to clean all the fans & intakes - including the fins on my Artic Freezer 7 Pro Fluid cooler. Since it had been barely a year since I built the system I wasn't prepared to see how blocked the fins were in the Artic cooler (my bad). So I'm guessing fried cpu, but since I had it opened up I went ahead and checked my OCZ 700 PSU with my PSU tester and it showed only the 5v light. Hmmm...

So... I have a spare 750w PSU (that I know is good) and, using it, I plug in ONLY the main 24pin and 8pin 12v connectors and it would come on for half a sec and then shut down. So I pulled the CPU cooler and CPU itself and all the RAM, but results are the same. It would come on for half a sec and then shut down.

Here's my question(s):

1- I've never tried to "power up" a system board without a cpu installed, but would it (the PSU) normally keep running and the system board just complain about the missing CPU or would it try to power up and then immediatly shut down?

2- Before I buy another system board and or CPU are there any other checks I can do to pinpoint where the problem is?

Thx in advance for all input... :)

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#2 CohenTheBarbarian

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Posted 21 December 2010 - 05:37 AM

If the processor is faulty, the board may or may not at least attempt to POST, but with no processor or a totally dead processor.. well, there's nothing to boot. It can't complain because there's nothing to do the complaining. I guess it could just sit there and stay on and do nothing, but it might as well just turn off.

Edit: I guess that was of no real help. Basically it could be either of the two components, or both. Is either part under warranty?

Edited by CohenTheBarbarian, 21 December 2010 - 05:52 AM.


#3 MrBruce1959

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Posted 21 December 2010 - 01:03 PM

Chances are if a component emitted that much of a smell to fog a room with, the device has to have some physical evidence of being over-heated or burned up.

Take the motherboard out of the computer case and examine it under very intense light.

Check all circuit traces on both top and bottom of the motherboard for burned or glazed areas.

Check all components such as resisters, voltage regulators and electrolytic capacitors for burns, or mechanical bulging of the component.

Check any IC chips for possible burn through marks.

Using a magnifying glass would be most helpful.

Bruce.
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#4 grindy

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Posted 21 December 2010 - 02:32 PM

If the processor is faulty, the board may or may not at least attempt to POST, but with no processor or a totally dead processor.. well, there's nothing to boot. It can't complain because there's nothing to do the complaining. I guess it could just sit there and stay on and do nothing, but it might as well just turn off.

Edit: I guess that was of no real help. Basically it could be either of the two components, or both. Is either part under warranty?


I've never attempted to power-up a system without a CPU before and was wondering if not having one would cause the PSU to shut down immediatly, like this one does.

And I should have included some basic specs, which are:

GIGABYTE GA-EP45-UD3P LGA 775 Intel P45 ATX Intel Motherboard
Intel Core 2 Duo E8500 Wolfdale 3.16GHz
2 G.SKILL 4GB (2 x 2GB) DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit

Chances are if a component emitted that much of a smell to fog a room with, the device has to have some physical evidence of being over-heated or burned up.

Take the motherboard out of the computer case and examine it under very intense light.

Check all circuit traces on both top and bottom of the motherboard for burned or glazed areas.

Check all components such as resisters, voltage regulators and electrolytic capacitors for burns, or mechanical bulging of the component.

Check any IC chips for possible burn through marks.

Using a magnifying glass would be most helpful.

Bruce.


Will do.... thx

#5 MrBruce1959

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Posted 21 December 2010 - 02:57 PM

Okay please keep us posted.

I got busy with the telephone and sent my reply before I was actually finished with it. :whistle:

You can check the CPU for glazing, this would be most noticeable on the under-side of the unit, the side with the pins on it.

Glazing or dark brown spots in this area are indicators that your processor was subjected to very intense heat. I do want to mention though, that most processors have a built in defense system that protects the processor from actual critical permanent damage.
The processor with this built-in feature is designed to shut down the processor before the core is permanently damaged.

Now I read back into your opening post and seen where you stated you were rendering some video.
There is a possibility your Video graphics accelerator is the possible culprit here.
Are you using an integrated video card or are you using an expansion card for video graphics display?

If this is an expansion card, can you please post the make and model number?

If it is an expansion card, please check the expansion slot for problems and check the video card for burned marks or glazing.

As for your initial questions, can you power up a motherboard with-out the CPU?
Sure you can, but the motherboard won't do anything since the system BUSS is not functional since it has to pass through the CPU before going to the various other parts of the motherboard.

Its like taking the cross roads out of the intersection of a road way. All four streets become dead-ends so-to-speak because the intersection (CPU) was removed. :thumbup2:

Hope this helps your understanding a little bit and please post back anything you notice during your inspection of your motherboard.

Kind regards.

Bruce.
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#6 grindy

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Posted 21 December 2010 - 04:57 PM

You can check the CPU for glazing, this would be most noticeable on the under-side of the unit, the side with the pins on it.


There doesn't seem to be any "glazing" or anything unusual.

Now I read back into your opening post and seen where you stated you were rendering some video.
There is a possibility your Video graphics accelerator is the possible culprit here.


I got the same results (immediate shutdown)with the video card pulled.

As for your initial questions, can you power up a motherboard with-out the CPU?
Sure you can, but the motherboard won't do anything since the system BUSS is not functional since it has to pass through the CPU before going to the various other parts of the motherboard.


I understand that the motherboard won't "do" anything without the CPU, but will it cause the PSU to immediatly shut down?

Is there any way to determine if the CPU is at fault or the mainboard itself (other than buying one or the other only to find out that it's the "other"?

Thanks much for your help here.... :)

#7 MrBruce1959

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Posted 22 December 2010 - 06:06 AM

To answer your question, which by the way is a very reasonable question if I might add.

Your power supply is self contained, it supplys the power.

However, the PSU needs something to tell it to power up, this would be a controllor chip which is located on the motherboard.

The power from the PSU is sent to the motherboard, from there, there is a controllor chip which is wired to a switch which is usually located somewhere on the front of the desktop's computer case.

Things are a bit different for a laptop however as far as layout goes, but the principal is still the same here as well.

Now when the button on a desktop computer is pressed, it sends a momentary signal to the controllor chip.
Once the chip recieves this signal, it sends a signal of its own to your PSU.
This signal activates a chip built into the PSU, which in turn, sends a signal back to the motherboard which is the different outputs from the different bridge rectifiers, such as 12 volts positive, 12 volts negative, 5 volts positive, 5 volts negative, 3.5 volts positive and so on.

The 20 to 24 pin plug which comes from an ATX power supply is a two way network of wires, some send signals from the motherboard to PSU and others send signals from the PSU to motherboard.

Its basically a communications network of both current flow and momentary signals which command things to happen as they are needed, such as powering up or powering down the power supply. Which is what happens when windows is told to shut down the computer, it sends a signal to the controllor, which in turn sends a signal to the PSU to shut down current flow to the motherboard and all devices which are also powered by the PSU.

I am a bit tired here, its early in the morning here, but if you think about it, if the PSU is controled by the motherboard and the motherboard is not part of the mix you are testing the PSU with, there is no way the PSU will power up, that is unless you make the connections the controllor chip would make.

Now seriously, there is a way to test the PSU without the motherboard being part of the mix here.
In order to do this, you have to jumper two wires together to make the PSU think the motherboard is connected to it.

Here is a simple way to chek this.

Please follow the instructions below, this will allow you to test your PSU to see if it can power up successfully.

WARNING: THIS POST MAY CONTAIN DIRECTIONS THAT INCLUDE WORKING WITH LIVE VOLTAGES OR PARTS INSIDE A COMPUTER'S POWER SUPPLY THAT CAN CAUSE SERIOUS ELECTRICAL SHOCK OR SERIOUS BURNS, A POWER SUPPLY CONTAINS VARY LARGE ELECTROLYTIC CAPACITORS THAT ACT JUST LIKE A BATTERY OR VOLTAGE STORAGE DEVICE, THOSE AND OTHER ELECTRONICS FOUND INSIDE A POWER SUPPLY CAN STORE DANGEROUS AMOUNTS OF ELECTRICITY HOURS OR EVEN WEEKS AFTER ALL ELECTRICAL CURRENT HAS BEEN DISCONNECTED FROM THEM! PLEASE USE EXTREME CAUTION AND COMMON SENSE WHEN WORKING WITH POWER SUPPLIES OR AC VOLTAGES!


The purpose of this procedure is to bypass the motherboard to test a ATX PSU.  Some manufacturers Like Dell have used some non ATX PSUs which have a different pinout for the 20/4 pin connector, please confirm that your PSU is a ATX type before using this procedure.

Caution:
This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock.  Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer.  For safety purposes please follow the instructions step by step.

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.

Posted Image
www.playtool.com

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.


This concludes the testing of the power supply, it helps to determine if your power supply is functioning or not.


Hope this helps you somewhat in determining if your power supply is the culprit or not.

But it also helps explain to you why the motherboard has to be fully functionable for the PSU to be fully functionable.

If you have a motherboard with a CPU missing from it, the controllor chip also does NOT function either.

Therefore, if you try powering up a computer with the CPU missing, there is nothing to tell the PSU to stay powered up, so it shuts down as soon as the power button on the case front is released.
This switch is a momentary type switch, you push it, it creates a momentary circuit, release it, and its an open circuit again. Once the controllor chip takes over by being powered on from the momentary signal, the switch no longer needs to create a closed circuit. In fact pressing the switch again, either tells the controllor chip to shut down the computer or go to suspend mode.
These last two options I just mentioned, have to be either setup inside the system BIOS utility under the POWER MENU, or through Windows power management settings.

I do realize your PSU is NOT the problem becuase you switched out the other PSU, so I posted the above information so you have a better idea of how the PSU relies on a signal from the motherboard in order to not only power up, but also to stay powered up.

Bruce.

Edited by MrBruce1959, 22 December 2010 - 06:37 AM.

Welcome to Bleeping Computer! :welcome:
New Members: Please click here for the Bleeping Computer Forum Board Rules
 
My Career Involves 37 Years as an Electronics Repair Technician, to Which I am Currently Retired From.

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As a Volunteer Staff Member of Bleeping Computer, the Help That I Proudly Provide Here To Our BC Forum Board Membership is Free of Charge. :wink:

#8 grindy

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Posted 23 December 2010 - 07:13 PM

To answer your question, which by the way is a very reasonable question if I might add.

Your power supply is self contained, it supplys the power.

However, the PSU needs something to tell it to power up, this would be a controllor chip which is located on the motherboard.

The power from the PSU is sent to the motherboard, from there, there is a controllor chip which is wired to a switch which is usually located somewhere on the front of the desktop's computer case.

Things are a bit different for a laptop however as far as layout goes, but the principal is still the same here as well.

Now when the button on a desktop computer is pressed, it sends a momentary signal to the controllor chip.
Once the chip recieves this signal, it sends a signal of its own to your PSU.
This signal activates a chip built into the PSU, which in turn, sends a signal back to the motherboard which is the different outputs from the different bridge rectifiers, such as 12 volts positive, 12 volts negative, 5 volts positive, 5 volts negative, 3.5 volts positive and so on.

The 20 to 24 pin plug which comes from an ATX power supply is a two way network of wires, some send signals from the motherboard to PSU and others send signals from the PSU to motherboard.

Its basically a communications network of both current flow and momentary signals which command things to happen as they are needed, such as powering up or powering down the power supply. Which is what happens when windows is told to shut down the computer, it sends a signal to the controllor, which in turn sends a signal to the PSU to shut down current flow to the motherboard and all devices which are also powered by the PSU.

I am a bit tired here, its early in the morning here, but if you think about it, if the PSU is controled by the motherboard and the motherboard is not part of the mix you are testing the PSU with, there is no way the PSU will power up, that is unless you make the connections the controllor chip would make.

Now seriously, there is a way to test the PSU without the motherboard being part of the mix here.
In order to do this, you have to jumper two wires together to make the PSU think the motherboard is connected to it.

Here is a simple way to chek this.

Please follow the instructions below, this will allow you to test your PSU to see if it can power up successfully.

WARNING: THIS POST MAY CONTAIN DIRECTIONS THAT INCLUDE WORKING WITH LIVE VOLTAGES OR PARTS INSIDE A COMPUTER'S POWER SUPPLY THAT CAN CAUSE SERIOUS ELECTRICAL SHOCK OR SERIOUS BURNS, A POWER SUPPLY CONTAINS VARY LARGE ELECTROLYTIC CAPACITORS THAT ACT JUST LIKE A BATTERY OR VOLTAGE STORAGE DEVICE, THOSE AND OTHER ELECTRONICS FOUND INSIDE A POWER SUPPLY CAN STORE DANGEROUS AMOUNTS OF ELECTRICITY HOURS OR EVEN WEEKS AFTER ALL ELECTRICAL CURRENT HAS BEEN DISCONNECTED FROM THEM! PLEASE USE EXTREME CAUTION AND COMMON SENSE WHEN WORKING WITH POWER SUPPLIES OR AC VOLTAGES!


The purpose of this procedure is to bypass the motherboard to test a ATX PSU.  Some manufacturers Like Dell have used some non ATX PSUs which have a different pinout for the 20/4 pin connector, please confirm that your PSU is a ATX type before using this procedure.

Caution:
This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock.  Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer.  For safety purposes please follow the instructions step by step.

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.

Posted Image
www.playtool.com

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.


This concludes the testing of the power supply, it helps to determine if your power supply is functioning or not.


Hope this helps you somewhat in determining if your power supply is the culprit or not.

But it also helps explain to you why the motherboard has to be fully functionable for the PSU to be fully functionable.

If you have a motherboard with a CPU missing from it, the controllor chip also does NOT function either.

Therefore, if you try powering up a computer with the CPU missing, there is nothing to tell the PSU to stay powered up, so it shuts down as soon as the power button on the case front is released.
This switch is a momentary type switch, you push it, it creates a momentary circuit, release it, and its an open circuit again. Once the controllor chip takes over by being powered on from the momentary signal, the switch no longer needs to create a closed circuit. In fact pressing the switch again, either tells the controllor chip to shut down the computer or go to suspend mode.
These last two options I just mentioned, have to be either setup inside the system BIOS utility under the POWER MENU, or through Windows power management settings.

I do realize your PSU is NOT the problem becuase you switched out the other PSU, so I posted the above information so you have a better idea of how the PSU relies on a signal from the motherboard in order to not only power up, but also to stay powered up.

Bruce.


Thanks Bruce for your very detailed suggestions. You certainly go the "extra yard" for us, and we are grateful.

I checked the PSU for basic operation with the paperclip and it cranks up just fine. Both the Gigabyte board and the Intel CPU are under warranty from them, and I just finished getting RMA's for both of them. One of the two is defective (at least) so I may get my original back from them if it passes their tests, which is fine. At least I don't have to spring for new ones.

Cheers




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