Vintage record players like the ones produced by the German company Dual are still popular today because of their excellent workmanship and sound. I have the privilege of owning one and using it regularly. Unfortunately it began making an annoying rattling sound lately. This is how I repaired it: The first challenge is opening the record player. I found this video explaining how this is done for Dual record players. The following picture shows the inside of the device. The mechanical constructions for the automatic movement of the arm are absolutely amazing!
The rattling sound was caused by the motor, which is located in the lower center of the picture. In order to get rid of the noise, you have to disassemble the parts surrounding the motor and oil them well. Afterwards the record player should work smoothly again. If this does not help, it might be necessary to disassemble the motor itself as explained here.