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.

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.


LeslieT29 (author)2016-05-14

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.

LeslieT29 (author)2016-05-14

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,


rabelyea (author)2012-06-22

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.

bluescrubby (author)rabelyea2012-06-22

Are you sure your batteries still hold a charge?


How can you tell?

fractalthinking (author)2010-01-06

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.


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.

tmaiorca (author)fractalthinking2011-11-13

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.

jimluschen (author)tmaiorca2011-12-12

I like Pink Floyd too!

stress_guy_53-30 (author)2009-04-18

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!


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!

rdb4179 (author)2013-04-02

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.

caisson (author)2011-08-10

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.

zer0vector (author)caisson2013-02-20

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

bluescrubby (author)caisson2011-08-10

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!!

poodyken (author)bluescrubby2012-10-08


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.


caisson (author)poodyken2012-11-01

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.

penwah114 (author)caisson2012-10-02

You seem to really know what you are doing. I am on my second Advanced unit and I have a lot of brushes left, I really don't know what is wrong, the brush is working, but I just noticed the charge light went off, so I am thinking I am running out of time. the unit is only 2 yrs old. I read your thread and I do not have any of the tools or skills necessary to fix this. any way you would be willing to help with this?my email is

amtrak23 (author)2013-02-04

What has happened to these boards? The one that is real bad was a brand new, unused, handle that was still sealed in the clam shell.

The other one is my brush that I have had for 5 years. The oring was fine and there was no evidence of moisture on the inside. The batteries on both are fine, so it's not corrosion from a leaking battery.

Why do the boards turn black, especially on the one that was never used, and how do I clean them up??

dubyayoung (author)2011-01-29

Great instructions on removing the battery!
That being said, when I removed the guts to my handle I found that there was some corrosion on the bottom of the circuit board. The battery was fine, no corrosion showing on it, and there was no apparent moisture inside. I brushed off the corrosion, and the circuit board appeared to be in very bad shape (see photos).
I contacted customer service to see if it were possible to get a new board, and it is not. And since this unit is out of warranty they weren't going to do anything for me but offer a 15% discount off of a new one.
After complaining a while, and one escalation, they actually agreed to send me a whole new handle!

Sonicare board 2.jpgSonicare board 1.jpg
dubyayoung (author)dubyayoung2011-01-29

By the way, this is from an HX7500, in case anyone was wondering. Forgot that little detail.

deroby (author)dubyayoung2012-09-04

This looks EXACTLY like my HX7500 does. Couple of days ago it stopped working overnight...
It now makes a (very) faint noise and most strangely the LEDs build up one by one until the entire bar is fully lit (all 5); then waits quite a while (2 mins?) and then everything goes out again.

Before that it held plenty of charge (~2 weeks?) so I'm pretty sure it's not the battery that needs replacing. Pried it open nevertheless and although the 'blackening' is not as progressed as on the picture above right, it sure looks very alike. I haven't de-soldered the battery (yet) so can't really say how the other side looks. Scraping off the blackness reveals it has eaten quite deep into the circuit board.

Not sure how long I have this thing ... must be over 5 years I think, I very much doubt Philips will offer a replacement. Thankfully I still have a (much less advanced) model that takes the same heads.

bluescrubby (author)dubyayoung2011-01-29

Good job!

rocketrancher (author)2012-09-02

(sharing this here and also with the "sonicare 7300" thread)

I, too, suffered the brush's short-cycle personality after replacing the battery.  After charging, I lost a tick on the gauge on the third day and on the fourth it went to zero and sounded the three-beep low battery alert.  If ignored after another day, there was still plenty of power but the brush would shut itself off mid-cycle and emit the single, long tone for deep discharge.

The battery reset procedure that appears on many sites, allegedly confided by Philips, is hogwash. The put-it-in-the-charger-and-press-the-power-button trick is described in the use instructions and only enables/disables the easy start power ramp for the comfort of a new user.  Any correlation with battery charging or endurance is a fabrication or coincidence, at best.  Also, the doomsday theory about Philips programming the death of the product is unfounded, as I am enjoying a nicely renovated Elite.

This may be the answer many are waiting for:  Yes, there is a battery quality monitor/charge controller "gas gauge" and it can be reset.   Exact design is not obvious, but it seems similar to Unitrode's bq2014.  Some have reset it by accident but here is a deliberate method:

First, disassemble the brush  if it's not already apart.  We'll assume the battery has just been replaced, so drop the inner assembly into the charger and give it a full charge by the level gauge.  Then, take it out and look at the board, just below the clear diffuser for the LED's.  There will be two square pads near the word "reset".   These are of interest.  Also nearby is an oval pad labelled "vcc".  Leave that one alone. 

Next, secure the assembly in a padded vise or have someone hold it securely on the bench top while you press the "on" button and then jumper the two "reset" pads.  This can very easily be done with probes from your voltmeter, allowing you to verify ~3.3 volts across the pads when the brush is "on", and then cross the probe tips and let them touch.  So far, you will know two things:   The gauge indicated a full battery when you switched the brush "on", and then the brush switched itself "off" when you shunted the reset pads.

Now, drop the thing into the charger again and you should see the gauge indicate an empty battery.  Allow it to complete another charging cycle, which will take overnight, and then reassemble the brush.  The recalibrated battery monitor should now offer a full reading for two or  three  days, gradually ticking-down over two weeks to the recharge signal, and then another three or four days before the deep discharge warning.

Advice here:  Use silicon grease on the o-ring, not sealant or aqueous gels that turn to glue, like K-Y.   The electrics are sustainable, as long as you can get to them, and there is no need or excuse for butchering the case. If it is fouled with pasty drool residue, run warm water over the joint and scrub with a toothbrush between attempts to jack the unit open.  Once it starts moving, use no more water. The o-ring will do its job; just make sure the board and case interior are dry before reassembly.

rabelyea (author)2012-06-21

Hello, Really appreciate the info found in this thread. Particularly the bit about how to open the device without destroying it.

One day I noticed one of my My FlexCare Toothbrush's seemed to have lost it's connection between the brush head and the motor armature. Since I've dropped it a number of times it seemed like a plausible situation. After learning how to open the toothbrush (thanks to this thread) I was surprised to discover that a couple of parts were missing! Considering how this this is built/designed and since I'm the only one living here I can only assume a house guest must have dropped it as well causing it to pop open and in the process it lost a couple of parts.

Can anyone direct me to a place for replacement items? Specifically I'm looking for the screw and V-shaped wedge that connects the armature to the head assembly (see image) I've checked out Sonicare's site but they don't seem to offer actual "parts" replacement items other than heads and chargers.

Thanks for any info.

bluescrubby (author)rabelyea2012-06-21

Rabelyea, I have no idea about spare parts but I assume they would be very hard to find and purchase, as the Sonicare is meant to be a single unit, and is not intended to be repaired. I would say your best bet might be to find a non-working one on ebay or craigslist that you can buy for $3 and take apart. Good luck!!

skylimey (author)2010-08-22

Hi Guys, My HX6930 died, so I pried the bottom plastic plug out of the base and the entire assembly fell out of the plastic toothbrush. Its a hi-power Ni-Cad (SE US14500V) and I'm guessing mine died because it's all wet inside. The battery seems to be in pretty good shape, so if it dries out, maybe it'll start working again. I just need to waterproof the gap between the head and the plastic. M

ARS1111 (author)skylimey2012-03-01

The Internet says that "SE US14500V" is a Lithium-Ion battery. Also, AFAIK, your model is a Flexcare series unit. Philips says these about Flexcare batteries:

"FlexCare uses Lithium Ion batteries. The batteries will last for many years of regular use. The Lithium Ion batteries inside your FlexCare toothbrush cannot be replaced. However, when they no longer function, they are easily removed for disposal, along with the handle. These Lithium Ion batteries do not contain heavy metals like Cadmium in NICD batteries, so they are much less hazardous to the environment. But they do need to be disposed of safely.
Do not throw away your brush with normal household waste at the end of its life... [...Here was the instructions how to dismantle the unit and remove the battery for disposal...]"

davejohnson01 (author)skylimey2011-08-18

Skylimey, how did you pry off the plug on the bottom?

The metal post on my HX6910 came loose and I want to see if I can fix it.


Jafafa Hots (author)2006-06-01

I only wanna know one thing - how'd you get the damned thing OPEN?


There are 2 slots at the top, where head screws on. Use one or two flat head screw drivers, alternating back and forth, to pop it apart.


Does it unscrew or pull out or what? I tried to unscrew it and am having no luck.

chomot (author)chomot2007-06-10

Oh I have the Ultra if that makes a diff

chomot (author)chomot2007-07-14

Hay I figured out how to open up the Ultra 7500 and similar. First remove the gray rubber tab from the back of the device, just opposite of the buttons and just below the threads. To do this use a thin bladed knife and pry up on both sides. It may take a bit of force as it is held in pretty tight by two tabs that go through the handle side and into the threaded top that locks it all togather. Then screw on an old brush head with the insides wrapped in paper towel or similar to support and protect the inside. The old brush head will but used to protect the outside of the threaded part from the tools you use to grab the top with. Using pliers or a bench vise etc gently but with some force rock it back and forth at the same time you are pulling strait out. It will not twist as it has keyways to insure the position of the handle case to the top part, so do not try and twist it. Just rock it back and forth until it pulls strait out. The threaded part will crack easily so be gentle but forceful. There are lugs in the threaded part that go into detents in the handle is what you are pulling against. From there the batt replacement is strait forward. Enjoy

mikoma (author)chomot2011-08-21

Great instructions, thanks! came right off with some wiggling.

My problem is with the green rubber on/off button on the HX 7500. Does anyone know where to get a replacement button? I went to the Philips website and of course all the want to do there is sell me a new unit.

I'm going to try some rubber glue on the button for now. Otherwise, this unit has been going strong for almost 4 years now.

Thanks again chomot for the instructions.

ibcj (author)mikoma2011-09-09

Did you have any luck with this Mikoma? I have the same problem with mine and am trying to figure out how to reattach the green button cover so that it doesn't get stuck when I use the power button. Seems like any adhesive on the button and/or case will not be strong enough to keep the button from getting stuck between the handle and the "guts" of the handle.

Please let me know your thoughts. And thank you!

mikoma (author)ibcj2011-09-09

Yes, I used "Instant Crazy Glue - Advance Gel Formula" and it worked fine. I guess it's been few weeks now and its hold fine. There is some residue on the green button, and it doesn't look like new but it works. I do have to push the button a little harder now to activate the brush on and off, but it works.

I just carefully applied the glue both to the outer edge of the button and the inside edge of the hole where it belongs. Kind of like using contact cement. One has to work quickly because the glue flashes off quickly, gets dry. Then I placed the button gently but firmly into the hole. I let it dry about 24 hours before I tried pushing the button.

You have to have a good "aim" to align it the first time because that glue is so sticky, I don't think I would have had a second chance. Would have had to mangle it to get a second chance. I think it is key to use the gel type glue because the non-gel is so runny I might have had a mess. I wished I had used some thin plastic gloves or something (like I always wish I had when I use that glue). But it wore of my fingers in a couple of days . . . and maybe the gloves would have stuck to the button, and that would have been a mess too.

It might have helped me that the green button was partially still attached, albeit by a thread. But I would still have tried it even if it wasn't.

I'm really happy because it saved me the cost of a new brush when the old one was working fine. I had the same concern as you, getting the button stuck, and water/moisture getting into the guts. Good luck.

StElmo (author)chomot2010-06-13

Right on - that opens the sonicare 7800 too. Mine was crusted so to get gearpuller like leverage I put a 2" length of thin 14ga wire once around the outer perimeter and twisted the cap down onto it.


You have to wedge 2 screw drivers in the gaps and pry them appart. don't know about the ultra...

dlsiegel (author)2011-05-02

I've been encountering a problem with my 5000 series since I dropped it a few days ago. It will no longer run for the full brushing cycle, cutting off after two or three of the 30 second intervals. I've placed it on the charger and it appears to charge fine, so I'm wondering if this is a battery problem worth opening it up for, or if it is something else altogether. Does anyone have any ideas or suggestions? Thanks in advance.

holykal (author)2009-08-25

First off thanks to bluescrubby for starting this Instructable. I know it's a couple of years old but I just read it so maybe someone else will get some good from this. After I cracked my 5000 series open, I measured the batteries and they were fully charged! I had to desolder the + terminal to remove the pack from the circuit, let it set for awhile then reattached the + terminal and the unit started flashing like it needed recharged. I figured this was a normal part of the subroutine so I placed it on the charger overnight until it quit flashing and now gives a solid green light. It has been working normal for over a week now. I am beginning to believe the built in obsolescence theory. The batteries are always attached so there is no way to reset the processor (mine has a Zilog Z8). Maybe it's just a fluke but I think that's why one reader saw a flash then his unit started working again. He probably just shorted power to ground creating a reset.

WMUNN (author)holykal2010-02-04

Great thread! Hope I can add some info and get a question answered.

I have a HX7500 Sonicare. I replaced the single sub A battery with an exact replacement NICd. Like everyone says a pain, but doable. (I worked as an electronic tech for quite some time, so not a newbie :-)

After replacing the battery and giving it a long time to recharge, it seems to run for a good many brushing cycles off the charger. (I always fully charged, then took it off the charger stand until the batteries were very low even though Philips says to leave constantly on charger.)

My HX7500 has the multi-LED row that is supposed to show battery charge level. However, no matter how long I leave it on the charger, when I remove it from the stand after 1-3 brushings it goes directly to the 1 amber LED "low charge" level. If I ignore this I will continue to get a large number of brushings. So it looks like the charge indicator really isn't measuring the battery, but maybe counting brushings. This seems likely since I have also read somewhere about the brush having a "learn mode" although I can't find that info now.

On this model, if I put it on the stand and hold down the ON/OFF button for a couple seconds it will toggle between emitting a single or a double beep. This is different than the sensitivity/ramp up mode which is on a second button on my model. I wonder if this could be putting the unit into or out of a learn mode? If so, what are the details of making it learn?

Also, inside the HX7500, there is a RESET pad. It is two adjacent solder pads meant to be shorted. I'm familiar with these from other devices and it would appear to be a manual processor reset. That did not solve the problem either.

I've tried multiple combinations of settings and charge cycles, but never seem to get the indicator LEDs to show brushings left.

Since the unit comes from the factory showing a relatively accurate reading I imagine they had another way of setting the unit.

BTW, I ordered three replacement batteries (Sanyo KR-1500AUL) from for $19 delivered by Priority Mail. They do have standard 1/4" solder tabs, so I had to add a short length of bare wire to connect to the 7500 circuit board.


50_Oama (author)WMUNN2010-12-04

Thanks to all, fixed my model e9800:

CHOMOT: Excellent tip on how to open the case. "Rock back and forth" is the key! Takes some patience, but once the o-ring seal is cracked, it slides out easily!

holykal: Thanks for mentioning the processor reset. Since none of my LEDs were lit, my symptoms sure smelled like a confused CPU to me (and not battery-related).

WMUN: Thanks for mentioning the reset pad. Since I didn't know which pads might reset the processor, I took a chance and used my screwdriver to short various pads that were on the circuit board ("below" the battery, if handle held w/brush-side up). After about 6 seconds of trying the possible combinations, a press of the on-off switch resulted in one of the LEDs going on. It was like getting a new pony for Christmas. It recharged normally thereafter.


1) e9800 seemed "dead"...LEDs would not illuminate no matter how long it was left in the charger.

2) Use rocking motion (not twisting) to easily access the "guts" of the handle.

3) Reset the CPU by removing power via short.

4) If none of your LEDs illuminate, it might be a glitch that is not related to failed batteries.

Boo-boo confessions, if you are interested:

a) Removed the rubberized portion of the handle to see if there was obvious access points underneath. Don't bother. See CHOMOT post instead.

b) Since the unit seemed "dead" (and not "limping"), I tried the Fonzi technique of giving the handle a few solid raps against the counter. If there are cold solder joints, or inadvertent shorts caused by residue build-up, sometimes the Fonzi trick works wonders. 'Course, I usually try this as a last ditch effort, I should have consulted Instructables first!

Thanks again everyone!

bluescrubby (author)WMUNN2010-02-04

@WMUNN, great input, and thanks. 

bitor (author)2010-04-22

***Another Way To Replace Your Batteries***

First off, Thank you for the direction and commentary on this subject.
While on vacation I had dropped my older sonicare and after that it did not work.
So, I decided to open it up like I normally do on things in general. This was before I came across these directions. I cut along the seam and opened it up. To my surprise two double AA batteries in some epoxy. I tested one and it read ok, but the other one was dead. So, I knew I had another older sonicare brush that I acquired because of my friend getting a newer one and this older one I thought would be a back up when my previous one went bad sometime in in the future. I knew it had worked before, but had not been charged for a 1 year or so.

When in my closet and put it on the charger..the light went on and the next day I decided to us it on  my teeth. Guess what? It did not work. The light was on but nobody was home.
Tried to reset the the sonicare, but this did not either have the reset built in or maybe the reset event is different for the older ones. So I looked at both of them and thought I'm going to replace the batteries in this unit because the were both the same size I decided to go about the replacement of the batteries a little bit different. 

The method here is good, but this to me after opening the first one did not seem piratical to open the whole brush to get at the batteries. To destructive for me. I decided to take measurements on the first one to calculate the exact spot where the batteries are and with the one that was not open, came from behind from the bottom up and cut the back side open at the top of the batteries and bottom. These two cuts would be parallel with the bottom of the sonicare base.
Next I cut one perpendicular and down the center between the two prevous cuts connecting them with this one cut. (Like an I beem)
This cut was made because of the epoxy that encased the batteries for easier removal of the outer case. Which would give me more sight on how to remove the batteries.
Next and very last I went across the mfg. seams to connect the first cuts.
So the whole cut was like a box with a single cut down the middle of the box with only the battery section half of the sonicare back side removed.

Then I took a screw driver's flat edge and placed it in between the second middle cut and twisted to remove the outer shell of the sonicare battery case.
It popped right off on one side and the other popped off after wedging the flat head of the screw driver between the outer sonicare case and the epoxy. Always keep in mind to try and hold the batteries so as not to stress the  joints on the PCB board.

Now what I had left was the batteries and the epoxy that had not all the way been cut throw on the first cuts.
My biggest concern here was not to break the connection from the PCB board. So I cut throw the rest of the epoxy so the only thing left holding the epoxy and batteries were the connectors from the PCB board to the ends of the batteries. This left me room to gently pull the ends of the batteries closes to the bottom out enough to get a small flat head screw drive in for prying.
I then simply place a small flat head screw driver in between the contact spot metal weld points of the batter and rotated/twisted the end until the spot metal area on the tops of the battery released. Now I could pull out the two batteries and replace them. Note that you only have to break the spot weld on the batteries' top closes to the sonicare button. The bottom doesn't need the spot metal to be removed in order for you to remove the batteries form the sonicare compartment you have made.

I know this is a lot of info and pictures would cut down this to half or more. But this I found to be a much better solution then slicing the whole sonicare brush in half. You will now have to do some soldering and could make so you could put springs in to just pop in and out the batteries when they go bad.
I just decided to solder wires to the batteries and put a rubber band around it for now. I will do something to seal the PCB board from the outside so water and etc. will not get in. I just did this so everything works great on it now. I've charged it and it works great.
The reason why the second older sonicare brush did not work even throw the light came on but would not charge is because one of the batteries leaked over time. That's it. As far as the first one I dropped on vacation, I don't know. Maybe it damaged something inside.

REMEMBER this is for the older sonicare brushes and not the newer ones.
Not to say this would not work for the newer ones.

I hope this gives a different angle on how to replace the batteries and inspires others to fix theirs this way. Less destructive and still keeps the integrity of the sonicare brush in tact.

Best regards

slogreen (author)bitor2010-09-04

@bitor. I followed your instructions to remove the batteries on my Sonicare that was no longer working. I have a nice clean cut and was able to access the battery compartment and remove the 2 AA NiCads. I tested them and discovered that they are charged. I tried two other NiCds, but it still doesn't work. Is there some sort of reset button on this model?

jeffreyi (author)2007-07-29

I went away for two weeks and left the sonicare unplugged. Returned home, plugged it in...not charging (no green light). Charger very slightly warm, so the power seems OK. Advice?? Thanks.

suzeliz (author)jeffreyi2009-09-05

Jeffrey - I just had the same experience - was on vacation for two weeks and when I came back my sonicare won't charge. Did you figure this out? Thanks, Susan

free.self (author)2009-08-10

How to open the 9000 seriers brush? I can't find a way in.

krush_groove (author)2009-04-20

Great instructions! These were a great help, I had to look at the picture to figure out which pin is positive when putting the new batteries in, it's a good idea to note this when taking the old batteries out. 2300mAh Ni-MH batteries are charging up pretty well so far and I used a hot glue gun to secure the batteries and seal the sides up. And if you can, recycle the old batteries :)

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