It seems the upper motor bush has run dry and worn, at least I can feel some play in it. I’ve been in the habit of leaving the deck running all day as the sound improves for the first hour after switch on, sometimes I forgot to turn it off before turning in for the night. This practice has been fine on previous decks with synchronous motors but the DC motor on the Artemis runs a lot faster.
The glue holding the pulley had softened enough that I could ease it off to get a bit of light synthetic oil to run down the shaft. I used a bit of Loctite 648 retainer to stop the pulley slipping, not sure about my choice there but it’s what I had.
The speed was still unstable with the Artemis ps at first but a lab power supply set to around 6.2V gave 33 1/3 rpm on a strobe disc, the current draw was initially near 0.1A but after running a few days this had dropped to 0.02A. With the main bearing nicely warmed up the deck would now run stably on the Artemis ps but the next morning starting afresh I was unstable again for an hour before I gave up. A few days later I started it up again and it settled after a few minutes.
Ideally I’d like to replace the motor and do it myself but the Artemis ps needs matching to the individual motor and I’ve not discovered how to do this, there are two trim pots inside the case so potential to get it really wrong. The lab ps makes the deck sound really ordinary so that’s not an option for running it. I’m resisting the temptation to investigate further, for now.