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Hello.

I have mining rig with 4 5870's. 5 months ago the TAGAN 950W PSU has burned. Till then i have mined with 3 cards on that setup.

Then i putted corsair AX850 PSU + noname 550W PSU together to feed up that mining rig. It worked just fine 5 months.

Yesterday i checked the Watts on both of the PSU results:

Watss total from the wall: ~ 980
Watts taking from wall AX850 ~ 960, (It has worked all this time with this wattage)
Watts taking from wall noname 550W = 5W (MAX)

So question is, what am i doing wrong? Why the Corsair PSU is taking all load to himself? Please help, i have tryed differnet variations, when i connect it like it should, one of the cards is not displayed.

Thank you for any usefull advices.

What is the noname 550W connected to? 1 card? 2 cards?
How are you getting that PSU to power on? maybe a pic of the setup would help.

Explain your setup a bit more. Which PSU is powering the motherboard, and which cards are running from which PSU? Also, how are you turning on the PSU that isn't connected to the motherboard?

To noname PSU is connected 1 card compleatly, and 1 card partly.
Each PSU has his own power cord. About how the atx cord is shortened, will post later.

Does the fan in each PSU spin up?  You may want one of these: http://www.newegg.com/Product/Product.aspx?Item=N82E16812201037

The second PSU is connected like this : http://www.youtube.com/watch?v=u0OKmIuNtmI

But PC is not using second psu at all, no matter how many cards is connected. If  i am using only noname 550W psu, i can run 2 cards on it, no problem, but when connected like second psu, it takes 5W from the wall. The corsair PSU is taking all the load and is hot like hell, but doing the job.

picture of rig wth closeup of psu connections please.
sounds like your 2nd psu isn't conencted to anything.

Cant make a picture now.

Any example, how it should work?

I don't suppose you own a multimeter, do you?

Also, I don't think you answered Cablez's question. Why you turn on the system, do the fans on both PSUs spin up?

Define "connected"

Most modern day GPUs require PCI-E power connectors, if those are coming from the 2nd PSU, then it will draw from that PSU, if not, it won't. Not rocket science.

If you're trying to jury rig some crazy contraption of daisy-chained molex converters between both PSUs, that's not gonna cut it. The only cross connection you really want is the on/off jumper. Otherwise just plug things in directly and you're fine. I do not recommend mixing connectors between the two PSUs, though it's not necessarily a hard and fast rule that I know of.

When i connect 1 card compleatly to 2nd psu, windows cant see it. When i connect 2 cards partly to one and another psus, it is working, vents are spinning, but no power from second PSU is taken. Do i need to connect both PSUs 24 pin motherboard 2 wires to get it worked?

I'm pretty sure you have connected something incorrectly.

A picture would  be worth 10000000000 words.

You have to make sure that the PSU that is not connected to the motherboard has its green wire jumpered to ground and is turned on by the switch on its rear.

Well I don't think you read my last post but I will try to help again anyway. It sounds like your 2nd PSU is not connected at all, that is why the GPU does not show up in windows when it is connected (it is not being powered). You have not really provided any description your setup, nor pictures, leaving people in the dark so I will assume that it is simply configured wrong.

I would
A) Not suggest you run this setup
B) If you really want to, try something like this: http://www.frozencpu.com/products/5637/cpa-167/Lian_Li_Dual_Power_Supply_Adapter_Cable.html

It will "bridge" the PSUs to the MB. They will both receive the "On" signal when you power up, and I believe some of the 3.3V will be shared (not 100% on that).  At this point, hooking up GPUs should work. The reason I said A is that the PSU not connected to all the bells and whistles of the MB/HDs/Fans/etc. is likely to go out of ATX spec when a heavy (dual GPU?) 12V load is applied to it (such as running a mining card) with little to no 3.3/5V load on it (the cheaper the PSU the more likely this is to happen). This means that it will supply power in a way that is not recommended, and potentially damaging. But that's your call.

Hope this has helped.

Yeah, sounds like 2nd PSU is not turned on to supply power.

Thanks to all, i got it working. 2nd psu is now connected to primary psu's - and are now feeding one card compleately. Strange thing thoe: it works only on rear card that is connected to pci-x1. Anyways, it works fine, with 1 card connected and a couple of vents on it it consumes totaly ~220W.

Just an update.

Today connected the rig to free eletricity facility.
Problem was on the 3rd card, which hanged computer, when started mining. Interesting, than after a wile it restarts whole rig. Probably something went wrong with cooling on that 3rd card, because now without any load on it, it reaches 79 degres, any more ideas, what went wrong? Yesterday all was fine. Thanks.

Had to lower clock speed to 300 nd memory to 150 to that hot card and still sits at 63 degrees. Its like no heatsink would be applied :( Too bad i will be abl to get my hands on it only after 4 days.

If any interested.
VRM's was hot like hell on that HD 5870 gigabyte SOC edition. Dont know, what ccousd this. I just putted accelero xtreme cooler on it and on vrms heatsinks from accelero cooler. Now the temps is very good.

I dare you to put this bad boy on along with your accelero: http://www.ebay.com/itm/Thermalright-VRM-R3-VGA-Heatpipe-Heatsink-ATI-5870-5850-/180525774685

Usually switching power supplies don't work or work very bad if you connect their + pin(s) together (if they work, one will win the war, unless you connect their bypass/whatever feedback pins together). You should have only ground (black wires) connected, anything yellow/red/orange should never meet in same board ( you said partly ).

Yes, from the beggining both psu's was connected with + , now when the minuses is connected, everything works fine.

http://www.straferight.com/photopost/data/500/medium/double-facepalm.jpg

This would have extremely helpful to have known earlier.