I got my dream video card, the ATI Radeon 5970 Dual GPU monster and installed it in my T7400 however the system will not boot up, all I get is a quick spin of the fans and some sort of sound coming out of the power supply, kind of like “Brrrnt, click” which led me to believe that the PSU couldn’t handle my video card.

The video card requires both an 8pin and 6pin power plug. When I plug in the 8 pin, and the 6 pin and power up the computer, it’s a no-go as above. when I plugged in only the 6-pin power plug the PC sounds like it will boot, the fans power up but no display as I would expect.

I have tried this video card in both PCI-Express slots with the same failure as the result. The computer works fine with the Nvidia Quadro 3700 in it…using one 6pin power connector.   I took the ATI Radeon HD 5970 video card to a local computer store and had it tested ($15) since I didn’t have a spare computer to test it in and the video card passed with flying colors…

Therefore I figured that my 1000 watt power supply had a problem, so as a gamble, I ordered a replacement off eBay and received a working pull plus the wiring harness and totally replaced both which was a job to say the least!! Have you ever tried replacing the wiring harness? lots of work…   I got it all back together, crossed my fingers and prayed and tried it again and the same thing.. NO LUCK…

I put the Nvidia Quadro 3700 back in and the system powered up like a charm.   What on earth could it be causing this to happen? I REALLY want to get this video card working in this system…   I even tried a bios update and thoroughly looked at the motherboard and everything I could to see if there was any popped capacitors.. nothing…

SOLUTION: (after much reading online)

I found the solution and I’d like to mention it here to help others if they search for it..

A: The Dell power supply for the T7400 was designed to have five 12 volt rails @ 18 AMPS each and the video card requires about 45 to 50 amps to work correctly. The video power cables (the one with an 8pin and 6pin both on the same harness) seems to only provide 18 or so amps and the computer will not power up because the power supply’s protection circuit sees too many amps being drawn from one “rail” and immediately shuts off..

I went to Fry’s Electronics in San Jose and bought a couple adapters that helped me split the current draw between different sources, such as the Hard Drive cables and the video cables.

B: I have a small battery backup power unit and my T7400 was plugged into the backed-up portion.. when I got the video card to work, it would make a loud beep and after a few minutes cut power to my T7400 due to large current draw.. I plugged the computer into a “Surge Protected” but not battery backed up slot and since then have had no problems..

Now after multiple stress tests including FurMark, my graphics card is working great in this system.. It is due to an unfortunate design in the T7400 power supply and cabling.. Now that I have this resolved I hope someone else can benefit..

Get an adapter like this, use it to split the power sources for the 8 pin power connector and use the original 6 pin that is connected to the Dell provided 8 pin adapter, for the 6 pin slot… hope that makes sense… through trial and error you will get it right!

Here is a picture of the main adapter and also of the smaller adapter to change from the molex to the Sata power connectors in my system: (I needed one of the adapter on the left and two of the adapters on the right.

Dual Molex to PCI Express 8pin adapter            Sata to Molex power adapter

I hope this helps someone!