All Philips Sonicare toothbrushes suffer the same common problems. The most common is due to 2 magnets inside changing position (often caused by dropping it). These 2 magnets need to be 0.5mm-1mm apart so that the vibrations can be correctly transferred to the brush. The magnets are held in place by 2 screws can can become loose. You need to open the toothbrush, adjust the magnets, and retighten the screws preferably with blue locktite. After I dropped my Sonicare DiamondClean ($220) the electronics worked but the brushing action lost all force. I followed this video and was able to repair it myself in 30 minutes and it works better than ever! The repair also gives access to the battery which can be replaced! https://www.youtube.com/watch?v=o3PBPU2jXbo