AMD R9 290x blank screen after 1 minute starting up

[stevenrader1]

Hi there! I just picked up an AMD Twin Frozr R9 290x for super cheap ( I knew the risk lol). I tested it for like 1 minute at the guys place but he had to go so I didn't run any benchmarks (riiiight). So my main problem is that the display goes blank after approximately 1 minute of starting up. I've tried it on two rigs same deal, both rigs run fine with my current r9 270. I checked thermal paste and it was sooo dry, cleaned carefully with alcohol and reapplied paste (noticed thermal pads on heatsink for ram, apparently this model overheats around 10 minutes cause of that normally). Apply new thermal paste didn't change a thing. Do I have a dead card?

This is the setup
The Beast:
- i7 3820
- x79 mobo
- 16 gb 2100 mhz ram
- Corsair TX850 bronze (running the card on single 6 + 2 pin connector cable)

NZXT:
AMD 6300
Republic of gamers mobo
8 gb of 1600 mhz ram
Corsair gold 80 plus 650 watt

 

[Calvin7]

Powered through 8-Pin + 6-Pin power configuration not by single 6 + 2 pin connector cable


System Requirement 750 Watt Power Supply (Suggestion)
1 x 8-pin AUX Power Connector
1 x 6-pin AUX Power Connector

 

[stevenrader1]

Powered through 8-Pin + 6-Pin power configuration not by single 6 + 2 pin connector cable


System Requirement 750 Watt Power Supply (Suggestion)
1 x 8-pin AUX Power Connector
1 x 6-pin AUX Power Connector

I'm kind of confused by your answer. I heard you're supposed to power this card through a single cord 6+2 pin.