Well, two months in and the electronics on the HBZ-2005 were getting more and more glitchy - lots of noise and clicking. I couldn't be arsed to send it back under warranty, so I decided to bin the original active circuit and install an Artec replacement. The first one arrived, was installed using the wiring diagram from the Artec website . . and didn't work. So I sent it back and got a replacement. Wired that in the same way, and it didn't work. A bit of probing with the meter determined that the wiring diagram on the Artec website was a little bit confusing, and swapping a couple of wires got the bass working again.
So at after a little bit of a short while I have got my 5 string bass back and working. Hussar!