The most likely things that occur to me are these:
Does the connector from the power supply fit snugly in the plug on the back of the B2:
If you flex the lead from the power brick to the B2, can you make the power come and go?
If either of those were to be true, it would point to the power supply assembly. However, if neither were true it does not rule out the PS.
But that's where I'd start.
I'm sure thoughts from others will be coming soon. :o)