After wrapping up a teardown (and unexpected repair) of a Philips product, I decided that was a good teardown theme and proceeded to another retired product from a different Philips subsidiary: Sonicare.

This Sonicare HX6530 could still vibrate the toothbrush head, but it could no longer clean effectively. Its degradation was long and gradual enough I didn't notice until my dental hygienist commented on my worsening dental buildup. I tried a new Sonicare and realized I should have retired this HX6530 long ago.

Some of the newer Sonicare have been designed to be easily opened for battery recycling, we just have to push on the metal toothbrush stem. This older model is locked up tight and not so easily opened. I thought maybe clamping the plastic will flex and break some glue joints, but nothing interesting happened.

Using my also-much-degraded Wondercutter (a topic for another post) I cut an entry slot and started prying away with pliers. I quickly got far enough to confirm there's a black rubber O-ring as water barrier.

More prying later, I reached a piece of black plastic that looked like a latch. Once all its surrounding plastic has been pried awayI tried pushing on the metal stem again.

Cutting one latch away weakened the holding power of the remaining latch, so this time a firm push on the metal stem was enough to push everything out of the enclosure.

There are definite signs of water intrusion inside, such as these dried deposits near the tip.

There was also rust near the interface between the coil and the armature. Unlike hair trimmers, reciprocating motion is not created here with a spinning motor shaft turning a crank. Instead it appears to be using a pair of coils facing a magnet.

I didn't see an obvious candidate to explain why this toothbrush degraded. The signs of water intrusion didn't seem sufficient to damage the electromechanical assembly, and all components appear intact on the circuit board. The battery voltage measured 3.8V DC, within nominal range.

I had expected the battery to be a single lithium ion cell in the commodity 18650 form factor. It turned out to be a much smaller cylindrical cell made by Sanyo. Here it is next to a 18650 cell for size comparison. Also visible to the left is the coil for interacting with the charging base.

I could peel three large pieces off the core. They are all made of soft vibration-absorbing material, the midships piece incorporated a spring for even more vibration absorption. It makes sense that keeping vibration under control would be an important mechanical engineering consideration for this device. It's not just for user comfort, they have to make sure it doesn't shake itself apart!

I was encouraged by the few Philips-head screws I could see at the base of the electromechanical assembly, thinking I might be able to disassemble it non-destructively.

That hope was dashed when I saw the other end of these two metal pieces were welded together. Oh well! Going further will be a destructive act. Before I do that, though, I want to probe the electrical aspects of this device.