Repairing Your Sonicare




Introduction: Repairing Your Sonicare

This thread has changed from a take-it-apart project to lots of advice on how to fix a Sonicare and put it back together. I hope all the great comments below help people bring their toothbrushes (or lockpicks or glass etchers or whatever) back to life.

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Step 1: Overview

Circuitboard with on/off switch, two AA size rechargeable batteries under.

Step 2: Top

This is the top coil, which controls vibrations to the toothbrush head. I know the head has magnets on it, but how does it work...?

Step 3: Getting Ready to Remove Solder

Here are the 8 points that have to be removed from the base. The 4 in a row are the connections for the top head; the 2 under that are the battery power leads. The bottom 2 are the recharger leads. Note all the corrosion...

Step 4: Finally!

Getting all the points loose was difficult, partly because many of the leads had wires soldered to them below the circuitboard and it seemed to replenish the solder I removed. I heat sinked with alligator clips and paper clips in the tighter spots.

Step 5: Circuitboard and Battery Pack

lines show corresponding leads.

Step 6: Corrosion

I tried to get it off with a toothbrush (don't tell my girlfriend!) but had to scrape it instead. Here's what it looked like...

Step 7: Semi-cleaned Circuitboard

And here's what the board looked like after I scraped off the corrosion. It looks like I might have damaged by overheating while trying to remove the solder, too. Beyond hope? If I cleaned it would it still work?

Step 8: Just for Anyone Who's Curious...

Here's what's under the blue capacitor (?)

Another note for anyone who's interested in changing the batteries: they are a standard size but they are epoxied into the base with the same stuff that holds the coils. Remove them by cutting away the plastic film surrounding the cells, remove the cells, and then pull out the plastic.

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    99 Discussions


    Question 2 months ago on Introduction

    Hi, I have a flex care sonicare I bought from Costco about 3 years ago that started turning on by itself and completely discharged the battery so it’s completely dead. I dissassembled it and found found the root cause of the failure: the top flexible seal failed (there’s actually a hole in it) and the circuit board and micro switches were corroded. I ordered a battery and top seal. As I was cleaning off the corrosion, R3 (330 surface mount resistor (I believe 33 ohms) detatched. I tried to solder it back, but it fell and is now lost. Can I just try to short out this circuit to get it to work? I’m not sure the solder pads are still good as they did not accept solder when I tried to solder them. I had planned to coat the front and rear seal in silicon grease to make them more waterproof. Please help. Thanks!


    Answer 2 months ago

    Sorry that I don't know the answer to this! This instructable is quite old so you'll probably have better luck elsewhere.The resistor is probably there for a reason but if parts of the electronics are already corroded then you may as well try... that's what I'd do at least.


    3 years ago

    Please Can somebody tell me what this part is and where I could buy them in the UK.

    Note please see my other post on this thread - im still getting to grips with the forum - sorry.


    Reply 2 years ago

    It's an inductive coil, simply magnet wire wound around a core. You should test the continuity of the posts with a multi-meter to make sure there is no break in the wire. If that is fine there is probably not a problem with it. It is far more likely that your batteries have failed. You can test them with the voltage meter of the multi-meter. If they are less than 1V they are most likely garbage and need to be replaced. They can be put into a AA Ni-Mh charger to see if they will charge.


    3 years ago

    Hi all, I would really love some help, and am really glad I have come across this website, can't believe I have never seen this before. I am a final year product design student at university in the UK, and I am designing a product which needs an induction charger like what is used on a toothbrush. So my question is what do I type in to find a condmuctive charging component/full kit like what is highlighted in the attached picture? Also, could youn recommend any UK based suppliers of such parts?

    Really appreciate any help on this.

    Best Regards,



    7 years ago on Introduction

    After leaving the unit on the charging base overnight now when I press the On/Off button the unit runs at high vibration speed for approximately 10 seconds then changes to a lower vibration speed for about 2 or 3 seconds then shuts off.

    I am able to select the various modes available as indicated by the LED's (cleaning, massage, etc. etc..)

    I have also pressed the On/Off button for 5 seconds while the unit is on the charging base and heard 2 beeps (although this action now seems to alternate between the On/Off button and the Mode button??...)

    The LED's light and the unit activates, the battery appears to hold a charge but it seems to be stuck in some kind of logic that I don't understand.

    I have also pried out the negative end of the battery to remove all power to the circuit board but no change.

    Can anyone tell me how to reset this unit properly or explain what it's doing?
    And what my next steps could/should be?

    Thanks for any help/information in advance.


    Most of the time, only the first cell of a NiCad battery pack is bad.  

    NiCads develop "wiskers" which can be fixed/destroyed by running higher than the normal voltage of 1.2v across them intermittently.  

    It is greener to try to fix it rather than replacing it.  

    In this instance it was also much easier than desoldering and replacing the battery.

    I usually use a 5V wallbrick and some tape to attach leads from the 5V plug end.

    I was able to fix mine with the battery in place.  1.3V after I  "sparked" the bad cell with 5V.

    Taking the sonicare apart was the most painful part.  It was a bloody affair after the utility knife slipped.

    The plastic also fractured. Now I have to make sure moisture does not get into it.


    Reply 5 years ago on Introduction

    After four years, you're not likely to comment, but maybe someone else will. I have an "original" Sonicare. Have opened it, and can see the batteries under the green board. Can't see getting them out. I don't know what a wallbrick is or how you would attach it to the battery to "spark" the bad cell. Is this dangerous? I doubt it.


    Reply 8 years ago on Introduction

    Like magic. But I still don't like it that they don't let us replace the batteries without the rigmarole. Boo to Sonicare! Careful with that axe Eugene. Thanks for the post. I saved about $60.

    For those who would rather let someone else do the dirty work, I found a guy on eBay who fixed my classic 4700 handle in a week (first class mail both ways) for $25. It works as good as new, and with three old brush-heads that would not fit the new handles, I took a chance and I am glad I did. Look for "Sonic Repair" -- I even gave him my first-generation handle for spare parts, and he overpaid me for the first-class postage. Great e-business person!


    Reply 6 years ago on Introduction

    howdy, stress_guy_53-30 , and thanks! I can try to find that dude, but any contact info. or hints for tracking him down would be appreciated!


    6 years ago on Introduction

    Great instructions. Thanks. I did a couple of things differently that worked well. I used to 750 mAh Ni-Cads from radio shack. I cut the unit open with an oscillating saw and glued it with hot glue. Cleaned up the case when finished with a Xacto knife. Total cost a little over $12.00 to fix two units. Great post and thanks for the instructions.


    8 years ago on Introduction

    Great repair guide re Sonicare Advance. I repaired 3 of them using the guide. My two-cents:

    1. Do NOT unsolder the pins. You may damage the circuit board. Instead, just cut the pins about mid way, to detach the circuit board. Why? See Note1 below.

    Putting it back:
       Use a 35W-40W small soldering iron with small, thin and sharp tip.
       Wrap then solder short thin wires to all the solder points at the device side, not to the circuit board. Naturally, use insulated and thin small wires.
       Align the board and solder the cut pins together. This holds the board in place, for physical strength as well. Use more solder on the pins for mechanical strength.
       If you cannot access the inner pins. Leave them unsoldered.
       Now solder all the short thin wires to the circuit board, copper foil side. All of them. The added wires help electric connectivity in case the solder on pins develops cracks. (There is whole lot of shaking!).
       As you can see, the inner pins that you did not solder, now has connectivity via the wires.
    Electric current is small, about 80mA, you can use as small a wire as you can. Make sure it is insulated though. Again, lots of shaking may rub away too thin an insulation.

    2. Use Xacto knife (or small thin knife) to scribe along the 2-halves on the inside of the screw-in head portion.
    This helps to ply open the 2-halves without cracking the thin plastic there. The smoother that plastic is, the better. The vibrating magnet of the brush head rests very close to it.

    3. When gluing the 2 halves together, use rubber bands to hold them together. Use your finger to smooth out or clean out the glue inside of the screw-in head area. Make it as smooth and clean as possible.

    4. I would not recommend silicone glue.
    It has ammonia. The acid attacks circuit elements and creates corrosion on circuit boards.
       Best is use acid free glue ("do not harm photo" type).
       One good example is Scotch Quick Drying Tacky Glue by 3M.
       You can get it at Micheal's or other arts suppliers.
       I use acrylic caulking, and use drops of Scotch Tacky Glue on corners and pressure areas to help holding the halves tight.
    The acrylic caulking inside the screw-in area is much easy to clean out, yet water tight. It would be a mistake to glue this special area tight. If you open it again, the tightness may break the thin plastic here. All you need here is water tight, not glue tight.

    5. Use 800mAh or higher NiCad, **NOT** NMH, Nickle Metal Hydride, battery. (Original is 700mAh NiCad.)
        NMH will work but you need to have the brush on charge constantly.
        Why not, when you can get cheap 2000mAh NMH battery? See Note2.
        You can buy cheap AA 800mAh NiCad at Harbor Fright, www harborfreight com.

    6. Normal AA has no tabs for soldering. You can add your own.
    Battery is sensitive to heat, be careful.
    Here's how:
        Charge the battery first so that you can test after you finish repairing.
        Add tape to the positive end, around the positive protruding tab, but not the positive pole tab itself. The side around the tab may have metal which is negative pole!!! You may short the battery by accident. Taping prevents this.
        File/sand the positive tab rough and shiny, or when it shows copper. Do the same on the negative pole.
        With a 100W-150W iron, solder a bare wire (24-18 gauge) to the poles of the battery. Or you can pull the flat soldering tabs out from the old battery and reuse them.
        How to solder it to battery:
          Wet the soldering iron tip (melt very small amount of solder on it.) The melting solder on the iron helps to transfers heat fast.
    Add solder to the battery pole with hot iron. When solder melts, remove iron, fast. Keep it under 10 seconds. Or let the battery cool down and do it again.
    Now add solder to the wire as well.
    Put the two together and add solder. The solders on the wire and battery melt together quickly. This helps to limit hot iron contact to less than 5 seconds most of the time.
    Tape the contact wires for now.
    Cut the contact wires to appropriate length when you put it in the battery cavity. (Length should slightly overlap the pins from the circuit board, to help soldering and mechanical strength.)

    7. You need to clean out the battery cavity of the handle as much as possible (rid of the epoxy glue). It is a tight fit. Clean much more at both ends of the battery cavity, for easy slide-in of the battery.

    8. Solder all other pins first.
    Keep the battery tabs taped. Battery tabs are to be soldered last.

    9. After all done and tested, THEN glue the battery in place.
    Tip: Can screw the brush assembly to 1/2 of handle for testing.

    10. Wait over night; allow vapor from glue to dissipate, before gluing the 2-halves back. (It would then be airtight trapping all vapors.)
    The circuit board is 2-copper-layer type with through holes. That means the hole is copper plated in the inside wall.
    Difficult to desolder and clean out solder. You may damage the copper trace or the board instead.

    NiCad has much lower internal resistance. That is, the voltage can remain flat for prolong operation (maintaining constant voltage).
    NMH, though has much higher capacity, the voltage slopes down as it depletes.
    Furthermore, the operational voltage of NiCad is higher, at 1.25V, compared to 1.20V of NMH.
    The difference is as high as 0.1V using 2 batteries.
    The circuit is designed for a flat voltage at 1.25Vx2=2.50V. If it falls below that, the circuit 'thinks' it needs charging. It blinks or may even refuse to work.
    You can overcharge the NMH, to higher initial full-charge voltage beyond the normal 2.40V. It fools the circuit that the voltage is high enough. That is why you need to keep NMH always on charge, if you use it instead of NiCad.
    It is not the battery's fault. It is the design that specifically to use NiCad.


    Reply 6 years ago on Introduction

    Unsoldering the pins wasn't a problem with a solder vacuum.


    Reply 8 years ago on Introduction

    Caisson, thanks so much for your reply! I'm really happy that you were able to repair three machines with the info here. The steps you include are really thorough, and would merit an instructable of your own if you feel like taking pictures to illustrate the process. Thanks!!


    Reply 7 years ago on Introduction


    I am 79 years of age and over my head in replacing battery for Sonicare Elite 9500. Per instructions, I replaced battery. And Sonicare still doesn't work. Could I send it to somebody who could be so kind as to find out problem and try to get it working. I would be forever grateful.



    Reply 7 years ago on Introduction

    Hi, poodyken and pinwah114,
    Here is an alternative.
    I bought from Walmart a Sonicare using replaceable AA batteries. It is about US$32-36. You replace the 2 AA by unscrewing the bottom cap. It uses the same brush head. Now you can reuse your old brush head. No waste.

    No more rechargeable problems. And you can use external rechargeable as well.
    The external-battery-Sonicare is also perfect for travel. I no longer need to bring the charger, and no fear of bad battery while traveling.
    Re: Replace battery but still not work.
    I encountered this initially, and wasted a set of batteries.
    The solution for me is to fully charge the batteries FIRST, before installing. Then, before gluing, screw the brush head to the 1/2 of the of brush (yes, it can). Test it. Then glue the 2 halves together. (Or, you can use rubber band to hold the 2 halves together for the test.)

    As mentioned elsewhere here, there is a 'battery gauge' built into the electronic chip that needs to be reset after changing battery. My way (full charge before install) is simpler and seems to work so far. Otherwise, do the Reset as mentioned in the blog.