[AndrewJ]

Gday Julian

The scope will ( normally ) happily run on 1.0-1.5A at max slew.
That said, based on your description, you are getting "Motor Fault" during booting, not a "Motor Unit Fault" when running.
( A MUF due to low power etc always results in an immediate reboot of the scope, with no beeps )
Sooooooo, if it is the former, ( and the constant beeping indicates it is ), then it is not normally associated with power supply.
On booting, the handbox asks the RA motor card what type it is, so it can configure itself accordingly.
If it gets no response from the motor card, it starts beeping and declares "Motor fault" ( which is a really confusing message )
If you hit enter whilst it is beeping, you can get past the warning.
Try the up down slew keys and they may work.
If they do, turn off the scope and swap the Hbx cable end for end and try again ( this swaps the wires used for the different comms functions ).
Does it now start up????
Also, what firmware is it running.

Andrew