Possible to Upgrade PSU on Dell XPS 720 H2C?

I have a Dell XPS 720 Desktop with a propitiatory Dell N1000P-00 PSU. I have measured the dimensions and counted up the various connectors and there seem to be a few replacement options out there, for example the AX1200i Digital ATX. However, the 720 has some Dell version of the nForce 680i LT SLI(C55P) motherboard which seems to require both a 24-pin ATX connector as well as a secondary 20-pin power connector. Anyone know if I am correct? Does this mean I'm out of luck and need a refurbished N1000P-00 or can someone help me identify a suitable replacement? The 1200i ATX is lacking a 20-pin but can I use some sort of adapter? Is one of the 1200i's EPS somehow suitable? Are there PSUs with both 24 and 20-pin power connectors? I have never done anything like this and would appreciate any guidance.

If it's helpful the manual for the 720 can be found here for reference. Information on the PSU starts on page 143.

Here is a comparison of the N1000P-00 and 1200i

Dell N1000P-00 1000W 24-pin ATX Power Supply

• Output: 1000 watts
  
• One (1) 24-pin ATX connector
  
• One (1) 20-pin connector
  
• Two (2) Large 4-pin Molex connectors
  
• One (1) 4-pin floppy power connector
  
• Six (6) SATA power connectors
  
• Two (2) 6-pin 6A power connectors
  
• Two (2) 6-pin 10A power connectors
  
• One (1) 6-pin P14 power connector
  

Corsair AX1200i Digital ATX Power Supply

• Output: 1200 watts
  
• One (1) 24-pin ATX connector
  
• Twelve (12) 4-pin peripheral connectors
  
• Two (2) 4-pin floppy power connectors
  
• Sixteen (16) SATA power connectors
  
• Six (6) PCI-E power connectors
  
• Two (2) EPS connectors
  

If the background as to why I am interested in replacing the PSU is useful...

I recently had to swap out my dual Nvidia 8800 Ultras for Dual GTX 570s do to a hardware failure. Unfortunately I now seem to suffer a sudden voltage drop with the new cards under significant load leading to an abrupt system shut down, no error message, no blue screen, just an immediate loss of power to the machine. It's also not a heat issue, I can restart right away. I have tested both cards individually and they preform fine alone it's only in SLI that I experience the crash. I can manually lower the maximum voltage for each card and avoid the issue but would rather not throttle them.

I don't know if the PSU is failing to provide the proper voltage to the rail (and don't seem to have any way to check, the Dell BIOS has nothing and the N1000P-00 doesn't seem to report voltages) or if I have overlooked something else but at this point I would like to replace the PSU if possible as it seems to be the issue.

Again any help or guidance is appreciated.

. However, the 720 has some Dell version of the nForce 680i LT SLI(C55P) motherboard which seems to require both a 24-pin ATX connector as well as a secondary 20-pin power connector. Anyone know if I am correct?

Thats weird...Never seen a MB like that or a PSU. I would have to say your going to have to get this directly from DELL or find a refurbed one.

I would really consider calling DELL to ask them about this because they often used proprietary PSU's with their systems and this definitely looks to be one. Any of Corsair PSU would only have one 24 pin connector and no way of adding a second like what is shown i your owners manual. TBH i thought you were reading something wrong at first, but reading your manual confirms what you are seeing..

I recently had to swap out my dual Nvidia 8800 Ultras for Dual GTX 570s do to a hardware failure. Unfortunately I now seem to suffer a sudden voltage drop with the new cards under significant load leading to an abrupt system shut down, no error message, no blue screen, just an immediate loss of power to the machine.

Trying to upgrade older DELLs is pretty tough. They are really funny about aftermarket parts sometimes. But what hardware failure did you have?

Are there PSUs with both 24 and 20-pin power connectors? I

Short answer is no. I also don't know of any other PSU manufcturer that would have one. It's not a normal ATX spec unit.

Thanks for the response. I figured Dell was making things harder for me...

Trying to upgrade older DELLs is pretty tough. They are really funny about aftermarket parts sometimes. But what hardware failure did you have?

One of my two Nvidia 8800 Ultras failed. I'm not sure what exactly happened but SLI stopped working and when I tested each card the damaged one was getting all sorts of artifacts and distortions. The on board fan wasn't working either. I had been assuming that the fan had failed and the card had overheated and been damaged. Why it didn't shutdown automatically if this was the case...

I have tested my replacement cards (Two GTX 570s) in each of my PCI-E slots alone and they work fine. I can also manually lower the maximum voltage for each card and avoid the crash so it seems like my problem is PSU related rather than motherboard related. Unfortunately the Dell N1000P-00 PSU and Dell BIOS has no voltage monitoring capability so I can't be sure...

Thanks again.

. I can also manually lower the maximum voltage for each card and avoid the crash so it seems like my problem is PSU related rather than motherboard related

This really sounds like a bad board.

But with that PSU being so funny it's hard to tell.

I believe you could still use the paperclip method to start the PSU to get voltage readings from the other connectors with a decent multi-meter.. This would at least give you a vote for or against the MB depending on how the PSU tests out.

If anyone is interested I purchased a replacement Dell PSU from a third party (Dell really wanted to overcharge me for a refurbished 750 W and refused to believe I had a 1000 W which they couldn't replace anyway). Everything is working now so it was some failure with the original PSU.

Thanks again for everyone's input.