Analysis: Star Adventurer Gearbox Error

Product Description
The following problem: The Star Adventurer starts normally, acknowledges switching the rotary switch with a red light, the motor noise can be heard, but the axle does not move.

We opened the Star Adventurer to investigate the cause.
The housing can be opened after removing the four outer screws on the housing.
We noticed that the motor shaft rotates on the encoder side, but not on the side of the actual drive towards the worm gear.
This initially narrowed down the cause of the problem to the drive side of the motor block.

To determine the actual cause, we want to open the motor's gearbox.
First, we remove the dovetail clamp for the prism rails. This requires loosening four screws.
Then we turn the ring for the RA clamp until it is loose and can be lifted off.
We have a clear view of the roller bearing of the RA axle. We carefully lift the roller bearing out of its position with tweezers.
We then remove the worm gear. It helps to screw two of the screws back in – the screws serve as a grip.
Once the four screws in the worm gear are loosened, the worm can then be easily removed with a slight nodding motion.
Next, we unscrew the two screws from the housing block that hold the motor block.
We free the motor again by unscrewing the head-side screws.
Once the motor is in our hands, we find two small screws that connect the gearbox to the motor on the front of the motor block. We unscrew these as well.
The gearbox is now free. We start the motor and see that although the gearbox rotates, the movement is not transmitted to the external shaft.
It is now clear to us that one of the gears in the gearbox must be the source of the problem.
The solution to the problem should be a replacement motor block.

To do this, we remove the engine block from a functioning Star Adventurer and replace the defective unit.

The functional test after reassembly reveals no abnormalities.