My machine is slowing down when I put the drum on the floor.

Bona Floor Belt Sander HD

The first two things you should check are correct power, and drive belt. Make sure you have the correct power for the machine. This can be measured with a volt meter at the end of the cord. Make sure the drive belt for the drum is not slipping. Even though the machine may sound like it is dying out, you may just be hearing the drum slowdown from the belt slipping.