OK - I've got a serious problem here. My main-board just smoked two Raspberry PI's. One will no longer come on at all, the other will turn the red light on connected to an external source away from the m-board, but a couple of the chips on the RPi get extremely hot very quickly, to the point where they burn your fingers if you touch them. I know that's not right.
The chip that now gets so hot on the RasPi is labelled RG2. I have one other m-board and a personal RasPi that I'll try, but I don't know for certain that the replacement board I received doesn't have the same problem - I've never tried it because I've been running both h-cards in one main board - the one that just smoked the RPis...
What was version of Mboard are you using?
Version 1. It's been running 24 x 7 since early this month. Noticed sudden hashrate drop at Slush. Sniffed. Smelled hot electrical components. Shut everything down. Chip extrememly hot, Raspberry Pi completely dead. Removed hashing cards, checked voltages on m-board. 5.06 on the appropriate GPIO pins. Shut everything down, plugged the RasPi into the m-board and powered up with no hashing cards in it. Red light came on and I had my hand on the back of the Pi on the side opposite of the chip that got so hot on the first one - it got very hot, very fast, so I shut down.
This Pi not as completely dead as the first one, if you remove it from the m-board and plug it into external power, the red light comes on, but that's it, won't boot, no light for the network cable.
Pulled the case of a third Pi that I had hashing with some Block Erupters and switched main boards. Worked fine. Tried both RPis in the second mother board - neither work. Switched over the hashing cards and am hashing with the second m-board...
At least I'm up and running again, but I appear to have a main board that went bad and produced two crispy, burned up, RaspberryPIs ...