Sonicare tootbrush teardown and repair

[reagle]

Just posted the writeup of my Sonicare toothbrush repair.
http://kuzyatech.com/philips-sonicare-hx6710-teardown-and-repair

Spoiler alert- I can't believe they don't conformally coat these things!

[amyk]

I can't believe it has a PIC! A toothbrush needs 14KB of program memory...?

But certainly, it would be even more surprising if it was an AVR.

Did you see if there were any interesting signals on the serial port? If I were you my curiosity would at least make me try probing and dumping the firmware, if only to see if they'd put some sort of self-destruct counter in there (unlikely, however.)

[george graves]

It would have been hilarious if there was a 328p DIP in there running an arduino boot loader.  Now *that* would have been funny.

[Stonent]

I think when Dave did his toothbrush teardown he found a microcontroller in it.

[amyk]

That was a 4-bit mask ROM (3kB) controller with 40 bytes of RAM, something more expected for this application.

[reagle]

Well, you gotta count time, blink lights and drive a motor- of course you need  all that memory!
I poked at the serial port pins and they were silent. Didn't have any PIC tools handy  to try reading the chip out- sorry. What I should've done, on the second thought, was to grab waveforms from charging and motor drive circuits, but I think I was more concerned with getting my toothbrush back and working.
I may have forgotten how to use the manual one

[NiHaoMike]

Are the A/D pins on the microcontroller connected to the motor coil? It's a resonant motor, so it might need some feedback to work properly.

[G7PSK]

Thats why I use those cheap dry cell tooth brushes that cost less than a couple of heads for a Braun brush, water always gets past the shaft seal not so much when being used but when stood in the charger a small amount of water remains on the shaft and then runs down it with the cheap battery ones I stand them with the brush end down and that seems to solve the problem of water ingress.

[reagle]

Well, might as well continue the consumer stuff line
I just posted a Schick razor teardown thread at https://www.eevblog.com/forum/reviews/schick-hydro-5-razor-teardown/

[IanB]

I have a Philips Sonicare toothbrush. There is absolutely no mechanical connection to the outside, only magnetic or electrical paths. Yet for some crazy reason the case is not sealed and moisture can get inside and mess up the electronics. As far as I can tell the only reason is design laziness or poor quality control. It can't be planned failure, because they have a warranty offering a replacement if it does fail.

[reagle]

Only 7 years later, but here is the newest failed Sonicare!
They did upgrade quite a bit of stuff I must say. Seems hackable, but I am a bit rusty on ideas..
https://kuzyatech.com/philips-sonicare-hx681a

[thm_w]

Interesting that they switched to cypress.
The NFC reading is a bit crazy. The field sensor makes sense at least, although I don't know why it cares if you picked up the brush or not. Hall effect I suppose.

[richnormand]

Did a similar job on my Oral B unit a few years back. Similar issue with corrosion and a weak battery (NiMH).

Of note was a plastic nib on under the bottom of the charging base molding. It was designed to fit and remove the toothbrush base cover without damaging it.
Have a close look at yours before using a screwdriver and damaging the bottom cover.

[m3vuv]

Simple get dentures!! lol