Here is a description of how I have chosen to replace the wired Potentiometer with an AS5045 encoder,
it is then controlled by an Arduino-mega 2560 where I have used K3NG software.
Inside the HAM-IV
Take a drill and make a small hole so you know where the center of the rotor is.
Then remove the bracket from the motor, you will have to drill out the 2 bolts that hold the bracket.
I placed the bracket in a machine vice, use a 3mm drill and place the bracket so the drill hits the small marking hole.
Mount an aluminum plate 30x70 / 1.5mm as shown in the picture, I used 20mm long hex standoff
it is very importen to have some space from the back of the AS5045 and the motor-shaft,
I have removede the back of the AS5045 whit a cutter, when you start the motor the shaft will move up so you have to get som free space for it.
Inside the upper part, where the normal potentiometer usually has a grip, there is a hole that fits the shaft that sits on the AS5045,
however, you just have to remove some of the shaft with a hand file carefully so it looks like the next picture.
Here, the shaft of the AS5045 is carefully adjusted so that it can fit in the hole.
Now you just need to reassemble the rotor, I have chosen to replace the terminal board which is at
the bottom of the rotor, with an aluminum plate where I have placed 2 PG13 fittings. 1 for the AS5045 signal cable and 1 for the motor control cable
LINK to AS5045 dealer DL1SR Georg
Here a short video of my HAM-IV whit AS5045