Cousin's PC will not turn on, trying to diagnose the cause.

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Jan 3, 2009
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Yeah, these are always fun since it could be just about any vital component and sometimes even non-vital ones that cause it. Hopefully this is the proper place to post this as I didn't notice a general hardware issues subforum, and I believe the issue is the PSU.

From what I recall, his specs are:
OS: Windows 7
CPU: i7-4770K
PSU: Seasonic SS-760XP2 760W
Motherboard: Asus Z97-PRO(Wi-Fi ac)
GPU: GTX 770, don't recall the make.
I don't remember the rest of the specs, but I don't think they are relevant to this.

My cousin told me that his PC suddenly stopped working and would not turn on, he sent me this video:

https://photos.google.com/share/AF1...?key=cWZOaVJwTUswdDNrRWxyYkwzU21McE4yb0FENl9n

I went over to check, pressing the power button just made the PC attempt to power on for half a second, then shut off, and it would loop like this until you did a forced shutdown.

The motherboard has a POST code display, but it would just show 00 on it, which leads me to believe that it's not even trying or getting able to POST before it shuts down. I really hope this means that the issue is likely something else and not the motherboard, especially since IIRC this model of motherboard can function in an emergency BIOS re-flash mode with nothing but a PSU and USB drive connected to it, not even a CPU.

Normally I suspect the PSU in these cases since that has almost always been the case in my personal experience. I removed the GPU just to be safe and connected the HDMI port to the motherboard's internal video, there was no video signal detected. I tried making sure all the connections were not loose, use different cables or ports on the modular PSU for the necessary power connections, etc, nothing. Even stranger the motherboard/PSU seemed to be keeping power (there is an internal backlit power button on the motherboard for testing purposes that acts as the case power button, even with the PSU's physical switch set to off and the power cable unplugged from the wall this button was still lighting up, unplugging the ATX20 cable was the only thing that turned it off) even with the physical PSU switch off at times. Nothing was making a difference until I attempted to run it with the additional (I think it's called CPU power?) 8-port connector removed. I wasn't expecting it to turn on at all or just keep looping since that is a mandatory power connector, but instead it stayed on this time and the video even flickered. It still would not POST since from what I understand that is a mandatory connection in boards these days, but there was some different behavior at least.

According to the PSU's manual all of the ports in that connector are just simply 12V, so I got a multimeter and tried testing them, but was surprised to find that they were all delivering 12V. I tried to use the multimeter on the ATX20 connector to see if anything there was delivering the incorrect or no voltage but could not get the probes to come in contact while it was plugged in. I tried unplugging the ATX20 connection and jumping the power-on pins..... but he didn't have anything on hand that I could use to jump it, the only insulated wire he had was speaker wire that was far too thick to go in the connectors. So we ordered a PSU tester, it's set to arrive on Tomorrow.

And there is where I am right now. I am not sure what else to do if the PSU tester shows up as the PSU being fine, so I wanted to ask for advice, both on what could be the case and what else I can try if the PSU turns out to be fine. The next part I would suspect is the motherboard, but I am not aware of any real way to test that short of buying another motherboard and completely disassembling and reassembling the PC, plus if we can't get the same motherboard that likely means a Windows reinstall as well.

Any advice or tips about this?
 
I had the EXACT same issue on an nforce2 board. It was the board. You could always test the psu by jumping the power wire to a ground. Lots of tutorials out there.
 
A friends machine did something similar a couple of months ago.
Was working fine then just shut off and wouldn't power back on. unplugging it from the wall for a bit then plugging it back in would power it on for a split second then shut off.
Turns out his GPU failed, it was an HD6950. Pulled the GPU out and the machine powers on. I put in my old HD5850 and it posted and booted up so I sold him that card for cheap.

I then tried the HD6950 in one of my PC's and the machine won't even power on with the HD6950 in the machine.
 
Do you have a spare PSU? If it's not the PSU, I've had that happen before and it was the board.
 
If your getting power to the mb but no boot its likely the mb or memory but most likely mb. If you cant find any burn or scorch marks on the mb it looks like its time to go process of elimination. If you have a rig with similiar specs i would haul his rig home and do the testing there using your known good gear. GL!
 
Unfortunately, I don't have any spare parts that are similar enough to test it with, anything that might be broken, I would just be guessing "this might be the broken part" and buying another of it.
 
It could be PSU, especially if the PSU on/off switch is not working. On any of your attempts did the LED go from CPU ON -> OFF Dram ON-> OFF VGA ON -> (repeat cycle)?
 
CPU, DRAM, VGA and BOOT DEVICE each have their own LEDs and go in the order of my post above, boot device being last.
 
I was working on a i7-7700k system the other day with a custom water loop. Because of the loop, parts of the case are a really tight fit to work in, and in the process of temporarily connecting an HDD to get the old data off of it I discovered that the machine would no longer boot. Even with the drive removed - it would no longer boot. You'd turn on the power, it would start flashing post codes on the little numeric display on the board (Gigabyte Gaming 7) and then power off for 2 or 3 seconds and do it all over again ad infinitum on it's own. I spent about 10 minutes watching this happen before I pulled the power plug to stop it.

It turns out that in the process of twisting my hand around the pump/reservoir to get the SATA connector plugged in, I bumped the RAM so that it was ever so slightly unseated. Reseating the RAM resolved the issue.
 
Sounds like motherboard, RAM, or CPU failure to me. This type of behavior is usually not indicative of PSU failure. Unfortunately, there is no real way to tell until you start swapping components, and no amount of posts on here is going to change that.
 
Take everything out of case and remove everything but 1 stick of RAM and the GPU and see if it will power up. If it will then start adding back the rest of the RAM and drives etc til it fails again.

Then goto local store and buy a PSU and try again. If that don't fix it then take it back with that RECIEPT you got and buy a motherboard.
 
I re-read your post and do think it is the PSU. The power light (by the mobo power button) should go off when you switch the PSU button to off. It might take 30s to do so but it should always go off after you switch the PSU off. If it only does when you physically pull the plug from the PSU then you have a defective PSU.
 
Casting my vote for motherboard or ......drumroll....faulty power switch on the case. As DrLobotomy suggests, the best start is to breadboard the PC. Put the motherboard on a piece of cardboard, plug in 8 pin and 24 pin connectors with a single stick of ram and the cpu only. Jump the power switch jumper with a flathead or similar (I use a pencil sometimes). If you still have the issue, pull the stick of ram and see if it beeps when you try to boot. You've just narrowed it down to either the mobo or psu (its not the cpu btw).

ps- you might smell the PSU. Weird, and probably past the point where this is applicable now, but a good habit when troubleshooting.
 
Casting my vote for motherboard or ......drumroll....faulty power switch on the case. As DrLobotomy suggests, the best start is to breadboard the PC. Put the motherboard on a piece of cardboard, plug in 8 pin and 24 pin connectors with a single stick of ram and the cpu only. Jump the power switch jumper with a flathead or similar (I use a pencil sometimes). If you still have the issue, pull the stick of ram and see if it beeps when you try to boot. You've just narrowed it down to either the mobo or psu (its not the cpu btw).

ps- you might smell the PSU. Weird, and probably past the point where this is applicable now, but a good habit when troubleshooting.
Damn I forgot about telling him to smell the parts. Always a good call.
 
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