Having read a few of the now closed threads on Arc and Beam power cables, I thought I would just share my experience having applied some of the advice suggested. 

I have a first generation Beam. It was all good for a long time, but at some point in the past year, the power cable became unplugged. I popped it back, the Beam returned to power, all good. Except it wasn’t. I began to notice intermittent loss of sound and realised the cable was very loose. 

A quick browse of the forum tonight, and a few people commented that the cable needs a firm shove into the socket to make it fit snugly. I tried, and can confirm that was the problem with my loose cable! So for anyone struggling with a Beam power cable that appears to be plugged in flush but is loose, just push it in more firmly, and it should slide in and become a nice snug fit.

Thanks to the tip on the now closed Beam and Arc power cable threads.