Oral-B 3772 toothbrash
Braun/Oral-B 3772 driver is a part of Pro 3 3000, 3500 and 3900 sets. This one was bought in June 2024 and failed in May 2026. Judging by the symptoms it looked like a battery or charging circuit failure, but it turned out later that this was not the issue. Toothbrush has gradually but significantly slowing down over a period of 3 or 4 days, up to complete stop.
https://toothbrushbattery.com/guides/braun-oral-b-type-3772-pro-3-3000-battery-replacement/ provides nice guide on disassembly. It is not difficult and it looks like it can be done without any big scratches or permanent damage. The hardest part seems to be pushing back top ring when reassembling - I've used old toothbrush head and a hammer.
14500 LiIon cell visible from the bottom.
No traces of water damage - it is sealed very well.
EFM8SB10F8G 8-bit MCU from Silicon Labs, 8051, 8 kB Flash, 0.5 kB RAM, internal RC oscillators, ADC, analog comparators.
Motor was completely open, not consuming any current.
Heavily grinded commutator, probably partially damaged brushes and lots of copper dust. Further disassembly would
be probably required to clean up the dust as rotor was partially locked. For me this seemed not fixable, probably
whole motor should be replaced along with spot-welded metal frame.
While it might have been used more than average over the last two years, this motor wear is disappointing, especially
when I'm comparing it to model 3764 (Triumph 6000) that worked for me for 8 years with similar usage pattern and failed because of rubber detoriation,
not mechanical or electrical failure.
Back to reviews / teardowns / repairs list.