Can't start PC after adding new PSU

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KILLZ0NE

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Apr 16, 2013
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okay, so I bought a new GPU only to find my power supply wasn't good enough. Now I've bought a power supply and my PC doesn't work. I know the PSU does, because I installed it in a friends computer, so I'm worried something is wrong with my mono.

When I initially powered up my PC after adding the new power supply the lights came on then it died. After checking we realized the atX12v1 wasn't plugged in. Could that have killed my mobo?? I've tried my old power supply and nothing. I cannot get my PC to turn on. I've unplugged everything. GPU, fans, drives, everything.
 
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T
Wish I had a good answer for you.

What could go wrong
1. Stress crack in the MB. The MB has several layers of wires/traces. Anytime you put any force on the MB there is a chance it will crack.
2. OLDer PSU that could not supply the voltage for the video card could have gone out of spec causing too much current.
3. Maybe what you did for protection from static discharge did not work (I usually touch the metal on the psu each time before i touch anything on the MB, some people use a ground wrist strap.) If you cross a carpet then touch the MB without grounding you can deliver enough voltage to fry the MB
4. Examine the capacitors on the MB for signs of swelling. Tom's has had articles in the past showing how to repair failed PSUs --...
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tsnor

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Nov 20, 2008
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Undo all the wires from PSU to MB and PC. Remove video card. Put in just the 4-pin (or 4+4-pin) and the atx 24 pin connector. Be very careful with the 4-pin (4+4) that connector will go in backwards. Does PC power up and beep no video? YES, then add video card with connector to PSU. NO, then put your old PSU back in and see if PC boots. If OLD PSU works and NEW PSU doesn't look for a cable problem on the new PSU. If both PSUs fail to boot then it's time to remove parts until PC boots, then add parts back in until it fails -- this process is outlined in the "no boot, no video" sticky
 
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Shaun o

Shaun o

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Oct 7, 2007
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It`s a lot simpler than that.
By not having the extra 12v ATX four or eight pin power block from the new Psu.
You have likely tripped a PSU protection circuit.

Simply turn the rocker switch off found on the back of your new PSU.
Switch the wall socket off that has the power supply mains cable connected to it.
Or remove the Plug from the wall for ten seconds.

Plug the wall plug back in for the power lead to the Psu.
And turn the rocker switch on the back of the Psu back to it`s original switched state.

And see the the system powers up properly after the procedure.
 
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K

KILLZ0NE

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Apr 16, 2013
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I've reduced the components all the way to nothing but the mobo/cpu and it still won't turn on :\ I've tried 3 separate power supplies (all of wich work for sure)

I've taken the mobo out of the case completely and the only thing plugged into it is a cpu fan , the cpu, and the psu
 
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T

tsnor

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Nov 20, 2008
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Bummer. So it is a bad MB, PSU or CPU. You've tried a different PSU and no joy. Most likely the MB is hurt. You can try blowing out slots in hope there is some dirt shorting something. The MB outside the case says you are not shorting against the standoffs or the case. Sometimes MBs crack as you push connectors and video cards in. Hope the mb warranty is still working for you. There is a very small chance the CPU is dead, but from reading forums it's always the MB or PSU.

Just to confirm, you have no memory in the MB, no wires attached even if no powered part on the other end. You have no video card installer nor any video hooked up to the MB. No disk, no sata cables. No usb keyboard or mouse. You are just looking for the CPU fan to start and the MB to use the onboard speaker to beep the bios code for no memory. (Your post reads like you did everything right, just double checking).

 
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K

KILLZ0NE

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Apr 16, 2013
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I had the motherboard/cpu, and the cpu fan and psu on my coffee table. The only wires connected were for the fan and the psu. No ram, no card literally nothing else connected. I tried again just now after checking the ports and checking for any imperfections. I didn't notice anything. I have no idea why it won't start. It was working fine! The components are about 4 years old so no warranty.

I just want to know why it won't start. I really don't want to pay for new components if they aren't broken. Is it at all possible that turning it on without that 8pin connector attached fried it? It turned on for a second when I initially installed the new PSU, but ever since it hasn't even flickered. I just want to know what went wrong, even if it is broken.
 
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T

tsnor

Splendid
Nov 20, 2008
3,702
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24,965
Wish I had a good answer for you.

What could go wrong
1. Stress crack in the MB. The MB has several layers of wires/traces. Anytime you put any force on the MB there is a chance it will crack.
2. OLDer PSU that could not supply the voltage for the video card could have gone out of spec causing too much current.
3. Maybe what you did for protection from static discharge did not work (I usually touch the metal on the psu each time before i touch anything on the MB, some people use a ground wrist strap.) If you cross a carpet then touch the MB without grounding you can deliver enough voltage to fry the MB
4. Examine the capacitors on the MB for signs of swelling. Tom's has had articles in the past showing how to repair failed PSUs -- older electronics have caps that fail, etc. MB's have a ton of those components.

Someone who knows what they are doing (not me) can literally peel the components and layers off the MB until they find out what went wrong. They do that at work when new generation parts fail. They use dyes to spot discontinuities and special lights. They need to know why the part failed so they can look for systemic issues instead of random part fails.

For me, it's not even 100% sure that the MB is dead, all that's known is several known-good PSUs could not get life out the the MB + CPU combo. Could be MB, could be CPU.

Update: "...Is it at all possible that turning it on without that 8pin connector attached fried it? ..." I've done that before. Thing worked fine when I finally realized what I did wrong and plugged in the 4/8 pin connector. This is a really common build error, it does not kill the MB. I've also plugged the second 4 pin in backwards (dummy). That MB worked fine also.

FINAL update: You did short across the power switch leads for a second or use your case power button to tell the PC to start....
 
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