No power at boot - previously working fine

mtnman

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A budget gaming rig that I built for my son was previously working fine (~6 months since last component upgrade). One day, it was like someone pulled the power plug while he was playing COD4. After that, it wouldn't boot. A few very small led lights on the motherboard would light up, but no power to any fans, drives, etc.

Parts:

XFX 680i LT motherboard
Pentium E5200
4GB AData RAM
XFX 9800GT 512MB graphics card ***
Rosewill 550 PSU

Nothing is overclocked, but the nVidia software was controlling fan speed. I pulled the 9800GT and replaced it with an old 8500GT and the computer works just fine now.

Based on my research, it appears that it could be the PSU or the 9800GT is bad. I have two other machines (my desktop and a WHS box) that I could try the 9800GT with to see if it had died, but wanted to get some other thoughts first. One machine has an Antec Earthwatts 430, the other has a Corsair 450.

Any guidance?
 

major53

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mtnman need to ask 1 question the rosewill has 2 -12 volt at 18 amp on each of them.how did you plug the xfx 9800 gt to the power supply?

* NVIDIA MINIMUM POWER SUPPLY REQUIREMENTS
o 400W or greater system power supply (with a minimum 12V current rating of 26A)

o One 6-pin supplementary power connector

the video card came with a 2 - 4pin molex cable going to a 6 pin power connector?
 

mtnman

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EDIT: I'm pretty sure it is this one:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182030

http://www.rosewill.com/products/s_387/productDetail.htm

The power supply has two 6 pin connectors. While working it was connected to one of them. After is stopped working I switched to the other 6 pin - no go.

Also, when I tried without any power connection a red light lit up on the 9800GT near the connector, card fans ran, but no video output.

New, beefier PSU? Something like a Corsair 650?
 
Definitly sounds like the psu. The fact that when you unpluged the 6 pin from the card and the fans started running tells me, the psu is too weak to power everything.

Rosewill isn't known for their quality PSU's. The antec EA 500w is a solid, good priced psu.
 

major53

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mtnman you are using 1 -12 volt 18 amp rail when you plug it up to the 6 pin psu connector.you need to use the small 2x4 molex going to the 6 pin on that video psu connector,the 2 seperate rails on your power supply should hook to that video power connector going to the video card.

your video card requires 1 12volt 26 amps. by using the small power cable provided by the video card the 2 seperate 12 volt rails that have 18 amps each can be combined to create the 26 amps that video needs.hope this helps you out.
 


The pcie connector will provide the power to the video card. Molex power doesn't go to the video, it powers fans and drives.
 

major53

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aford10 the cable that is provided by the video card has a pci express power cable that has 2 molex cable going to a 6 pin video connector.this is what I am trying to tell him to us. the psu you suggested is a better power supply but it has 2 12 volt 17 amp rails and when he plugs it up it will work for awhile then he will have the same problem down the road. the video card he has requires 1 12 volt 26a rail he's still going to have to combine the 2 12 volt 17 amp rails to get the right amps.
 

mtnman

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I tried the two molex to one PCIe connector...shown in this picture.

9800GTPVT98GZDL4Acc354x312.jpg


How do I know if the two molex power sources are on different rails?

I'm getting ready to go pick up the new PSU, but wanted to try one last time using the cable that XFX provided with the card.
 

mtnman

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BTW - the cable in question here didn't work...same result. Just wanted to know how to ensure I am hooking up one from each rail.
 

major53

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mtnman on the rosewill 550 you have 2- 6 pin connector and you also have 2 sets of molex cable that can be used too they have maybe 2 molex and a sata cable on them.you can use 2 molex from seperate rails to power the video
 

mtnman

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Ok, so if I use a molex two separate cables it should work? I'm pretty sure that is how I set it up...heading up to go check it out.
 

major53

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mtnman don't use both molex off the same wire 1 molex off of separate cables.
 

major53

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take the 9800 gt out and look to see if any of the caps are puffed up on the top of them.
 

mtnman

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Thanks for helping! :)

The caps all look fine.
 

major53

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mtnman if buy another psu buy one with 1-12 volt 32 or 42 amp 6 pin connector.


i hope I am explaining the connectors correctly.your power supply has 2 power connector that can be plugged up to the video card ( 6 pin ),also you power has 2 sets of molex and sata cable ,usually 2 molex and 1 sata on two separate cable to where you can plug (fans, cd,dvd etc) by using 1 set of molex cable from one line and another from the other molex line it gives you a total of 36 amp you can us to power the 9800 gt. the card I have has 2- 6 pin pci express connectors on the video card so I us both of the 6 pin pci exspress connector off the power supply to power the 9800 gtx and have never had a problem 3 years now.

 

mtnman

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Thanks - I do understand that I need to have two different cables, and use one molex from each when using the 6pin adaptor. That is what I have done and get the same result.

I think I'll go with a Corsair 650 (http://microcenter.com/single_product_results.phtml?product_id=0273361)

+3.3V@24A; +5V@30A; +12V@52A; -12V@0.8A; +5VSB@3A

Lot's of great reviews for this PSU, and 52amps on a single rail.
 

mtnman

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My question is why would this happen to the PSU (worked for 6 months then won't)? Surely something had to change inside it right? I mean, it just sounds odd to me and perhaps more like something could the card...is that crazy talk?
 

major53

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mtnman the psu aford10 suggest is a great deal (CORSAIR 650),and for why the rosewill falled 6 month later a good psu powers every thing in that pc of yours ,and you should alway buy a good psu it does make a big differents.
 

mtnman

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Well guys, I just tried putting the 9800GT in my server. It is a Corsair VX450 and has a 33A rail - same result. I only have two drives in that machine and no other components. I'm going to send the card back to XFX.

I understand that the PSU is important. But in this case it appears that the issue was over time, the under powering of the card killed. The PSU runs the computer just fine after switching back to the 8500GT. I'll upgrade the PSU, but in the end the card had crapped out (due to the underpowering).
 

major53

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mtnman your right that what I beleive too.sorry for your problems with the video card .good luck on the replacement and the power supply.(get a good one like the corsair 650 it has 52 amp and they make great power supply .good luck if need help again just post and someone will aways help you at tom's hardware