After looking over the circuit board and charging coil of my retired Sonicare (HX6530) electric toothbrush, only the electromechanical actuator assembly remains. Earlier in this teardown I noticed a few welds, that'll have to be dealt with at some point, but I'll start with the screws at the base of the electromagnet.

There were two of them, one top and one bottom. Removing the first one was undramatic. As soon as I loosened the second, though, there was a metallic "click" and it took me a few seconds to figure out what happened: as soon as the screws were loose, the electromagnet core slid up against the permanent magnet.

Manually prying them apart, I see the gap adjustment ranges from a maximum of almost two millimeters down to no gap which was where it went when the screws were loosened. This distance would affect toothbrush performance but I don't know in what ways, so I have no idea how to optimize this gap.

Here's a picture taken earlier intended to show rust as sign of water intrusion, but here we can also see the original spacing between permanent magnet and electromagnet. That is a tiny gap and I doubt I could restore that precise distance again. Then again, perhaps this distance is wrong: maybe its gradual degradation of performance was due to the electromagnet slowly sliding towards the permanent magnet over many years? Ignorant of metrics to measure proper operation, I have no way to tell.

On the other end of the actuator, I could access a single screw. Loosening it freed the toothbrush stem assembly, caked with deposit left from water that got past the rubber seal.

Everything else was enclosed inside the stamped sheet metal shell held with stamped clips as well as spot welds. I'm curious if it was originally designed to be held with just the clips. The welds may have been added to the manufacturing process later when they realized the clips along weren't strong enough, or maybe the welds were part of the plan all along.

A cutting wheel removed the welds, but the stamped clips were pretty strong even without them. I ended up cutting off one set of clips as well.

Once the top and bottom stamped sheet metal bits could be separated, I could extract the electromagnet and the pivoting lever sub-assembly.

Unscrewing the visible fastener freed the permanent magnet from the pivoting lever sub-assembly. The final fastener was hidden under the top plate of the pivoting lever sub-assembly, holding it together. Once undone, everything could come apart.

Freeing the permanent magnet also meant I can look at it under my magnetic field viewing film.

This was a lot more complex than I had expected. Once I saw this device worked by using an electromagnet to actuate a lever, I expected an one-piece arm with a magnet on one side and the toothbrush head on the other. I infer this complexity was required because they wanted to implement a very specific motion profile for optimal dental hygiene. All these parts allow them to fine-tune the motion: from changing the thickness of spring steel plates to increasing/decreasing the mass at either end of the lever. If they wanted to optimize production costs, it wouldn't need this much complexity to just vibrate a brush head. A cheaper and simpler knockoff could vibrate but not necessarily replicate the precise motion.

Would I notice the difference between a genuine Philips Sonicare and some cheap knockoff? Maybe yes, but maybe not alone by itself. I think I'll notice a difference with a side-by-side comparison. After using Sonicare for years, I think I have a good idea of what feels right. While a slight gradual degradation may go unnoticed as was the case with this unit, if something goes wrong overnight I'll notice. I'm confident because that happened with my next Sonicare.