I own my butterfly labs units for maybe 6 to 8 month. The power supply began to break 2-3 month ago. Since then, I am always working at 50% of my total hashing power.
Each week I have at least one that breaks, until now...
I replaced the original power supply by 2 pc psu. Hopefully, butterflylabs used the same pinout for their devices as the PCIe connector in PC PSU.
I own 6 single and 1 little single.
I power 2 single + 1 little single with the powersupply XFX XTR 750W
I power 4 single with the powersupple EVGA 1300W G2
Both power supply are 80 plus gold and I affirm that the efficiency of the stock power supply from butterfly labs is not as efficient as these power supply.
What is nice with the EVGA power supply, is that it comes with an adapter to power up the power supply even if there is no motherboard connected. Else, it would be needed to short 2 pin to power up the power supply. But, some of their PCIe connector have a lock pin too large for the butterfly labs enclosure. It is needed to cutout that pin.
As said in the title, the devices from butterflylabs are lifetime warranty, so it is easy to get replacement, but in forum few people are complaining that the power supply are taking fire. It is not a good idea to keep using them.
One of the problem I have seen, is that the fan is cheap. So it is stopping working fast. So the cooling of the unit become a problem and other components in the device break ...
I urge you to buy quality external power supply, it will help to lower your electricity bill and it will keep your room cooler as their efficiency is highly better.