Hi, my friend just got his brand new HD 3870 X2, we installed it, and as soon as we switched on the PC there was an intermittent beep from the case, and on the monitor appeared a dooming "you did not connect the power cable to your video card".
Now he got a:
ASUS P5K
Core2Duo E6750
2Gb DDr2 PC6400 OCZ
3x HD
Sound Blaster Audigy 2
everything powered by an Enermax 535W (18A on 12V)
we connected the video card with 2 6-pin pcie power cables.

So we thought it could have been the PSU, so we tried with my Cooler Master Real Power M520, (19A on 12V) that has an 8-pin pcie power cable, so we connected the 6- and the 8- pin cable to video card, and switched on the PC, but same message, same beep.

So we've got a Cooler Master 850W 80plus (28A on 2 12V, 18A on the other 2) (that has been used for some online reviews of the video card, so it should definitely work).... but we get the same message and the same beep.

Now I can only think of 2 things:
1> The video card is broken (and we have to find out soon)
2> The power multiplug (don't know how u call it in UK) that he's using can't give enough power for the PC, the monitor, the DSL Hag and the 5.1 speakers.

Please help us out!

Does any other vid cards work?

Doubt you broke the video card, are you sure you connected the second 6 pin connector in right? If you have a spare 8 pin connector then you can just hook in that, otherwise make sure there firmly in.

I've connected the 6-pin (on one of the 6-pin/8-pin cable) and the 8-pin (on the other 6-pin/8-pin cable) ....there are 2 more only 6-pin cables.

Strange thing is that TH review used a PowerColor and a CoolerMaster 850W just like me... and it works..

X1900XTX is working with all the PSU we've tried.

(thanks for the replies)

Have you reseated the card in the Pcie? If you have, sounds like a faulty card

I think I've found the problem.
The 6-pin plug on the video card is faulty. It isn't sitting on the board like the other 8-pin plug, but it's put 1/1,5 cm too high on the metallic pins, so the pins that go inside it are just 1 mm high INTO it, and I think the power cable can't reach them so that's why it says it isn't connected.

Now my doubt is, get it to my hardwarewhore friend that surely know how to make the black plastic plug sit back on the board or send the card back to the Ebay guy who sold it to me and wait who knows how much time to get it or the money back?

you bought the card off of eBay.... There's your problem. No one sells a new card off of eBay unless it's broken or they are scalping.

I hope you can get your money back. Xbit labs had reported that you could use two 6 pin PCIe connectors for the 3870x2 if it's not going to be overclocked (the 2nd six pin supposedly works in the eight pin power connector too).

I could not get mine to work with two six pin connectors in the Antec Neo 550 (it's the MSI factory overclocked), so I got an Antec Neo 650 with the 6+2 connector for the 8 pin and it works fine. Coolermaster psu's aren't that great (or weren't, maybe they've improved) so that could be an issue if it's not the actual plug on the 6 pin.

Never buy any GPU from Ebay. You'd have better luck with a Newegg open box.

Managed to get it to work, the plastic sockets aren't fused on the pins, so ONLY if you know how to push them down, you can do it and solve the problem

Some things with building and upgrading your own PC's you just need to learn through experience. Tech support is often no help either.