Ok, curiosity got the better of me and I opened up my B11. I had the switching compartment open once before, but that was some time ago and given this particular incident, I thought it might be a good idea to have another look. Several things concerned me somewhat. The AC power leads are riveted to the small circuit board holding the relay, four diodes, a resistor, capacitor and a coil (not sure it's a coil, just a guess). The rivets are fairly snug, but it's a mechanical connection and I would prefer to see some solder there as well. The AC power cord has no strain relief that I could see, which is another concern, given that the leads are only riveted to the circuit board. If someone inadvertently yanks on the AC cord, or if there is a continuous strain on it, that could cause a failure/short. Other than that, most of the components appear well mounted and soldered. So if the quality control is not up to par, you may end up with a unit with loose AC connections which is bad news. The relay is quite small and is rated at 1 amp for both the AC and DC side. Did not find a fuse anywhere in there. It's reassembled now and back in service on my tank.