…the slowly ongoing saga. Typical. I wired up the 50-way D connector and connected it all up and … nothing. On checking voltages half was missing, i.e. -80 was there but no +80. The barretter was open circuit on one side. Huh.

A new barretter arrived via eBay and so I now have the PSU fully working. A quick check of the 444 showed it to be no better than before, which I’d expected but I really wanted the correct power supply to verify that. So I connected up the TDMS to send data to the 444 and with the keys set to SMSMS it reliably prints Y – pity that should be R! Fiddling with switch combinations is equally confusing.

So, progress, of sorts. However, the TDMS itself needs work yet because the circular trace is far from a circle, or indeed not even close to anything which might be imagined to be circular.