Topic: maybe i'm don't understand power - problem with usb hub powering 3 BE at a time (Read 426 times)

I've been putting together a small hobbyist mining rig over the last few weeks and this board has been invaluable, thanks in advance for any help.

I started with one erupter a week ago and finally got two more in today.  I'm having trouble getting all 3 running on my usb hub.  

I'm running this on an old mac book pro laptop that i have around and i'm running bfgminer on the command line. I have 3 336 Mh/s USB block erupters and a powered usb 2.0 hub with a 5V/3.6A AC adapter.  I can get 2 block eruptors stable on the usb hub but every time i plug in all 3, 2 of them go dead.  

Is this usb hub just not living up to the power specs? Am I miscalculating the power needs that I have?  Something else?

For the time being, I'm running 2 BE on the hub on one computer and another on a my work computer's usb port because it won't fit into the USB plug next to the hub connector. I also have a small unpowered usb hub, that i tried plugging into the other port on the computer, but it couldn't seem to keep the BE going. I'd really like to get them all over onto the other computer so I can leave my work laptop alone. 

Oh yeah, and I already have a little BTC and I just put an equal amount of money (well BTC) to my spend on the rig into LTC and FTC on btc-e just yesterday as well.