Secondary PSU randomly shuts off

allen5055

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Mar 25, 2012
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I have a mining rig with two AX860 psu's that are connected by an Add2PSU adapter. Twice now my secondary PSU has randomly shut down while mining, which makes the whole system crash. I look at the computer and the primary PSU is working, and the fans connected to it are spinning, but the secondary PSU is off and the 3 280x's connected to it don't have fans spinning.

I checked the ADD2PSU and it's in all the way. Anyone have any ideas about this?
 

oblox

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Unless you are undervolting those 3 cards, you're potentially right up to the max capacity of the 860 since some draw around 275w or more.
 

collegeboy69us

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+1 on what oblox said.

I experimented with a dual PSU system on two of my mining rigs and you have to really pay attention to how much load you have on each rail and total system wattage, and all that jazz.

I was able to get five (5) 270's on the same 850W PSU, but that's pretty much the limit of what will work comfortably/reliably.

Try running just two 280's on your PSU (or two 280s and a 270) You have to remember that the CPU/hdd will take up a few watts as well.
 

allen5055

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No, they're undervolted and I've put them on a meter. They're pulling less than 700w.
 

edge929

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To rule out the PS just shutting down due to overload, take off the Add2PSU and just use the paperclip trick. You can turn it on/off with the switch on the back of the PS. This way it should always be on with the exception of a total power loss.
 

UncleDavid218

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Just FWIW, I run 3 280x overclocked on a Seasonic M12II 850w with no problems at all. I use the paperclip method of powering up the PSU.
 

collegeboy69us

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might be slightly related -- but I've had this issue pop up when it comes to weird power downs or crashes related to power.

When using USB risers - I had one of my PSU's overload a rail when I was powering three USB risers.

As I understand it the PCI-e standard allows for 75W to be supplied via the "board". If I was putting 75Wx3 on a rail to power the risers, I would get reboots/crashes sometimes.

My new setups I only will power two risers per rail. (so split them between the molex chain, and the two SATS chains that are pretty standard these days.
 

allen5055

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I switched the Add2PSU connector with another cable and the 2nd PSU went down again.
 
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