Hi Jauqq,
I hope that you're NOT using the separate Notator dongle as well as Log 3,
as Log 3 contains a Notator dongle itself! As you say, the contacts may need cleaning,
but also check the temper of the spring contacts in the connections of both Log 3 and
Unitor 2. This is a rare symptom but Barrie provided the answer for me some time ago
(thanks Barrie

).
The contacts that grip the spade connectors lose their springiness
(temper) over time and can fail to make contact, even if you've cleaned them. Simply get a
2mm screwdriver and GENTLY ease them together. Then when you connect Log 3 and Unitor all
together contact will be restored and Notator will be able to read the dongle inside Log 3
and make contact with Unitor. If Notator can't read the code on Log 3, that's why it hangs
up.
Hope this helps,
Best wishes,
Dave.
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Lots of Ataris which keep on going, 12 Kurzweil 1000 modules, a bunch of hardware synths. Still recording to tape -the old ways are best.....