Computer doesn't power on after installing second Radeon HD 6990

[coinminers]

I have the following computer that I have been using for mining:

- msi 890FXA-GD70 motherboard, model# MS-7640
- 1 Saphire Radeon HD 6990
- 1 SilverStone Power Supply 1500W, SST-ST1500

I recently bought a new card (Diamond Radeon HD 6990) which I installed into an available motherboard PCI slot and connected both power slots at the top of the card with the power supply. (I was trying to replicate the way the first card was wired that came with this machine. I noticed there were 2 cables with a tag saying 6+2PIN(PCI) +12V7 and 6+2PIN(PCI) +12V8, so I just some additional cables that came with the computer with the tags 6+2PIN(PCI) +12V5 and 6+2PIN(PCI) +12V6)

Then I booted up the computer. The screen flickered a few times but after about 1 minute it began booting up.

Then I started mining with the two mining tasks that I had set up for the two GPUs of my existing card.

Then the computer shut down. Now I can't boot up the computer anymore. The power supply doesn't even turn on.

I removed the second card and still, same thing, the power supply remains off.

[Zanatos666]

Well first things first, I would try a new PSU.  Start with the obvious thing.  If you arent even getting a spinning fan on it, it could be fried.  If not a new PSU, then a PSU tester.  Again, verifying that the one you have is actually functioning.

If you are getting power once plugged into a tester, then the board may be fried and not completing the circuit.  I fried a Diablotek 850w power supply a couple of months ago after about 4 months of mining with hit.  Was a cheap 850, not a good 12v rail.  Went back to my Sparkle one which I have been using for over a year now *knock on wood*

[wazp]

hmm, not sure on your cables(have been hiting numbers all day) but what you should try is
remove the ower cable, if you have a switch on the back of your psu let that be on.
hold the power button in until you empty all the power in the psu/mb (around 10-20 sec)

then try to start the pc up again

[HeavyMetal]

You may have exceeded the power available by your power supply. This happened to me when I made a 7 drive RAID array, everything was fine but when I spun them all up at once for a file transfer the whole machine shutdown and would not stop.

My power supply had a reset switch to clear the breaker, some have a fuse, some will reset on a timer, others will just fry. Either way the answer is a higher rated power supply.

[ssbtoday]

Hmm, you could have easily blown the fuse in the PSU. (Could have been a bad fuse)
Overload?
Short in the Cards?
Motherboard toasted?

[Snapman]

Yep, sounds like a blown PSU, it sux but it does happen especially during heavy usage like mining. Swap it out and try booting with only 1 gpu on the new setup, if that fails then the problem would lie with your mobo.