Braun electric toothbrush charging

[pedro]

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

 

[Bob Milutinovic]

"pedro" <me@privacy.net> wrote in message
news:henla990jimoqboma2k1vpvjdr79s3gc5d@4ax.com...

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.

Whereas with most battery-powered devices you expect the charge to gradually
diminish, with these units the base unit usually fails long before the
battery starts deteriorating. Almost invariably, the coil in the base goes
open-circuit.

Good luck in getting the base open (my one attempt revealed liberal use of
epoxy), and when (or rather, if) you do, good luck in re-winding the coil.
Given the time of year, you might just want to kill the proverbial pair of
birds by buying her a new one - it'll be far less hassle.

--
Bob Milutinovic
Cognicom

 

[pedro]

On Fri, 13 Dec 2013 22:15:19 +1100, "Bob Milutinovic"
<cognicom@gmail.com> wrote:

"pedro" <me@privacy.net> wrote in message
news:henla990jimoqboma2k1vpvjdr79s3gc5d@4ax.com...
The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.

Thanks for the quick reply, Bob. I realised it was an air-cored
transformer, but I allowed for the possibility that they were
operating at a higher frequency to get decent coupling efficiency. I
was still out looking for an AM portable to check if there was any
50Hz field around the base unit.

Whereas with most battery-powered devices you expect the charge to gradually
diminish, with these units the base unit usually fails long before the
battery starts deteriorating. Almost invariably, the coil in the base goes
open-circuit.

Given the 2W nameplate rating, that's a pretty high Zin - about 300K
if resistive. Some coil, so presumably a blocking cap to help keep
the current half-decent. There goes the prospect of measuring for an
O/C coil without cracking the case ....

Good luck in getting the base open (my one attempt revealed liberal use of
epoxy), and when (or rather, if) you do, good luck in re-winding the coil.
Given the time of year, you might just want to kill the proverbial pair of
birds by buying her a new one - it'll be far less hassle.

This one has the cord end of the wall unit seemingly retained in the
case with visible barbs on opposite sides of the case. They resist
decent efforts to depress them though.

If there is bugger-all of consequence in that wall unit, the only
reason for the size is as a handle for the tri-lobe tool moulded
thereon which undoes the toothbrush base.

 

[N_Cook]

On 13/12/2013 10:20, pedro wrote:

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

With an OralB charger base,DVM Fluke 77 and 1mH small choke near the
spigot of the base ,
measured 0.45V ac, HF not mains frequency but Fluke still registered
something

 

[John Keiser]

I would check the coil in the hand piece. Either try a different base or
open by twisting. The hand piece coil is accessible. I fixed one that had
opened and needed resoldering.

"pedro" <me@privacy.net> wrote in message
news:henla990jimoqboma2k1vpvjdr79s3gc5d@4ax.com...

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

 

[Andy Wood]

"Bob Milutinovic" <cognicom@gmail.com> wrote:

It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.

Interesting...

I always assumed that things like that did just drive a coil at the
mains frequency, and I was a bit surprised to discover that was not
the case for a couple of torch/nightlight combinations we have. I did
not bother to try to trace out the circuit, but it comprises bridge
rectifier, capacitor, a high-voltage transistor and not much else that
I can remember besides the coil.

A coil placed nearby one of those sniffs out a 23kHz signal.

These toothbrushes are obviously different. I wonder what make them go
down the one path vs the other?


Andy Wood
woodag@trap.ozemail.com.au

 

[Jon Elson]

pedro wrote:

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

The old ones (no idea what model #) have a simple charging circuit
of a diode and a coil in the bottom of the handle, and 2 Ni-Cd
batteries. I can't get that size battery anymore, so I rigged two
larger cells outside and taped to the handle. It has worked
for some time. I used to replace the cells every 2-3 years when
the wouldn't hold charge anymore.

Jon

 

[pedro]

On Fri, 13 Dec 2013 19:17:04 GMT, woodag@trap.ozemail.com.au (Andy
Wood) wrote:

"Bob Milutinovic" <cognicom@gmail.com> wrote:


It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.


Interesting...

I always assumed that things like that did just drive a coil at the
mains frequency, and I was a bit surprised to discover that was not
the case for a couple of torch/nightlight combinations we have. I did
not bother to try to trace out the circuit, but it comprises bridge
rectifier, capacitor, a high-voltage transistor and not much else that
I can remember besides the coil.

A coil placed nearby one of those sniffs out a 23kHz signal.

Interesting indeed. I have one of those combo devices here in bits
and did trace out the circuit. One greencap-type cap had blown its
guts and a resistor across it was cremated. Lacking values - and I
suspect these *may* alter the oscillator frequency - it remains it
bits. That 23kHz info may help reolve it.

These toothbrushes are obviously different. I wonder what make them go
down the one path vs the other?

The Braun certainly has an amount of electronics in it - see the video
here on replacing the battery in a 3738.

http://www.youtube.com/watch?v=um3ncK4FonM

 

[pedro]

On Fri, 13 Dec 2013 22:15:19 +1100, "Bob Milutinovic"
<cognicom@gmail.com> wrote:

"pedro" <me@privacy.net> wrote in message
news:henla990jimoqboma2k1vpvjdr79s3gc5d@4ax.com...
The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.

Whereas with most battery-powered devices you expect the charge to gradually
diminish, with these units the base unit usually fails long before the
battery starts deteriorating. Almost invariably, the coil in the base goes
open-circuit.

Good luck in getting the base open (my one attempt revealed liberal use of
epoxy), and when (or rather, if) you do, good luck in re-winding the coil.
Given the time of year, you might just want to kill the proverbial pair of
birds by buying her a new one - it'll be far less hassle.

Making sure we are using the same terms here: Wall unit = the flat
plug-into-the-outlet piece. Base is the coil assembly that the
toothbrush sits atop to be charged. Toothbrush = obvious.

I have a "search coil" of ~130 turns of 0.7mm wire on a bobbin.
Bobbin ID is 15mm and coil OD is 31mm.

Test #1: With the coil (unterminated) connected to the 15MHz CRO,
absolutely zilch on max sensitivity when the coil is sitting flat atop
the energised base. Definite flatliner.

Test#2: Fed an AC current of 1A through the coil and brought the
toothbrush right up to sitting on the bobbin. No interest whatsoever
on the battery status/charge LCD. I have forgotten all my inductor
stuff way back, but if the factory base has an input (label) of 2W
then this may well have had a comparable field give or take the odd
order of magnitude.

Just to be sure we are talking about the same product. The previous
generation product had a base-cum-storage-tower construction and the
base had a keyed spigot for locating the toothbrush with the charge
LED outwards. The one we have has an egg-shaped hole through the base
with a matching shape on the bottom of the toothbrush. The video of
battery replacement (link in my reply to Andy) shows the toothbrush
under discussion.

 

[Andy Wood]

pedro <me@privacy.net> wrote:

.. . .

Interesting indeed. I have one of those combo devices here in bits
and did trace out the circuit. One greencap-type cap had blown its
guts and a resistor across it was cremated. Lacking values - and I
suspect these *may* alter the oscillator frequency - it remains it
bits. That 23kHz info may help reolve it.

The two of those that I had both came from Aldi, but about a year
apart. They had the same Aldi product code, 37737, and were both
branded Delta, but the casings were slightly different.

Like yours, one of them died. I took a peek at it, but in the end I
decided I never was going to get around to trying to revive it so I
chucked it out.

I just had a look at the other one, which is still working, and found
there is actually a bit more to it than I was remembering from my
quick look at the one that died. Circuit could be similar to your one
but maybe not exactly the same. There is a 2k resistor connected to
the emitter of the transistor, but there does not appear to be a
capacitor connected in parallel with it.


Andy Wood
woodag@trap.ozemail.com.au

 

[William Sommerwerck]

I use both Braun and Sonicare toothbrushes. (I like variety.) The Brauns
charge fine on the Sonicare base (though they just "sit there", without even a
nub to hold them in place).

I have a few extra Sonicare chargers. I will gladly send one to any US
resident who needs one, for the cost of postage, plus 50 cents handling.

 

[Bob Milutinovic]

"pedro" <me@privacy.net> wrote in message
news:d4rna9tsrn596j30nansgj8l2mgafkgmdo@4ax.com...

On Fri, 13 Dec 2013 22:15:19 +1100, "Bob Milutinovic"
cognicom@gmail.com> wrote:

"pedro" <me@privacy.net> wrote in message
news:henla990jimoqboma2k1vpvjdr79s3gc5d@4ax.com...
The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.

Whereas with most battery-powered devices you expect the charge to
gradually
diminish, with these units the base unit usually fails long before the
battery starts deteriorating. Almost invariably, the coil in the base goes
open-circuit.

Good luck in getting the base open (my one attempt revealed liberal use of
epoxy), and when (or rather, if) you do, good luck in re-winding the coil.
Given the time of year, you might just want to kill the proverbial pair of
birds by buying her a new one - it'll be far less hassle.

Making sure we are using the same terms here: Wall unit = the flat
plug-into-the-outlet piece. Base is the coil assembly that the
toothbrush sits atop to be charged. Toothbrush = obvious.

I have a "search coil" of ~130 turns of 0.7mm wire on a bobbin.
Bobbin ID is 15mm and coil OD is 31mm.

Test #1: With the coil (unterminated) connected to the 15MHz CRO,
absolutely zilch on max sensitivity when the coil is sitting flat atop
the energised base. Definite flatliner.

Test#2: Fed an AC current of 1A through the coil and brought the
toothbrush right up to sitting on the bobbin. No interest whatsoever
on the battery status/charge LCD. I have forgotten all my inductor
stuff way back, but if the factory base has an input (label) of 2W
then this may well have had a comparable field give or take the odd
order of magnitude.

Just to be sure we are talking about the same product. The previous
generation product had a base-cum-storage-tower construction and the
base had a keyed spigot for locating the toothbrush with the charge
LED outwards. The one we have has an egg-shaped hole through the base
with a matching shape on the bottom of the toothbrush. The video of
battery replacement (link in my reply to Andy) shows the toothbrush
under discussion.

Right you are; it was the previous generation which I had, in which the base
was barely more than a small plastic disc and a nub-encrusted protrusion
with which the brush docked.

This morning I had a look at my daughter's newer unit, which has a slightly
wedge-shaped oval as the docking point, and that seems to have considerably
more bulk to the base unit - about an inch tall - which may likely house
additional electronics.

I still contend though that because of the relatively low price of these
units, it's not worth pursuing repair for any reason other than personal
satisfaction.

--
Bob Milutinovic
Cognicom

 

[William Sommerwerck]

I goofed somewhat. I have a couple of spare Braun chargers, as well. The offer
stands.

 

[pedro]

On Mon, 16 Dec 2013 04:09:35 -0800, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

I goofed somewhat. I have a couple of spare Braun chargers, as well. The offer
stands.

The offer is appreciated but as I'm "down under" and it would require
an adaptor to connect to our AU/NZ outlet, it's probably easier to
bite the bullet and purchase the replacement from the Braun guys.

 

[pedro]

On Mon, 16 Dec 2013 18:47:33 +1100, "Bob Milutinovic"
<cognicom@gmail.com> wrote:

This morning I had a look at my daughter's newer unit, which has a slightly
wedge-shaped oval as the docking point, and that seems to have considerably
more bulk to the base unit - about an inch tall - which may likely house
additional electronics.

The one we have is like this (but with Oz-pins of course ...):

http://www.service.braun.com/product/big_img.asp?artGrp=3731&partno=0067040173&l=GB&c=AU&pic=parts|xl|67040173_xl.jpg

Sorry about the URL mess.

I still contend though that because of the relatively low price of these
units, it's not worth pursuing repair for any reason other than personal
satisfaction.

That's the current Plan A. $34 plus $10 shipping from east coast, or
$39.95 ex the one local source.

Then I can do a Jeff Liebermann learn-by-destroying job on the
existing wall unit. Wedging a couple of flat-blades into the current
one showed what appeared to be the end of a pcb and clear silicon bog
filling the entire enclosure. There's something in there warranting a
pcb, and enquiring minds (this one at least) feel a need to know.

 

[Bob Milutinovic]

"pedro" <me@privacy.net> wrote in message
news:tsava9dr83kaa9l606m2p4bp7felk85i3p@4ax.com...

On Mon, 16 Dec 2013 18:47:33 +1100, "Bob Milutinovic"
cognicom@gmail.com> wrote:

This morning I had a look at my daughter's newer unit, which has a
slightly
wedge-shaped oval as the docking point, and that seems to have
considerably
more bulk to the base unit - about an inch tall - which may likely house
additional electronics.

The one we have is like this (but with Oz-pins of course ...):

http://www.service.braun.com/product/big_img.asp?artGrp=3731&partno=0067040173&l=GB&c=AU&pic=parts|xl|67040173_xl.jpg

Well that's an entirely different kettle of fish; the ones I've seen have
the male mating on the base.

This is my daughter's charging base looks like; mine was similar but much
thinner -
http://www.thepartsbiz.com/assets/images/84848387b.jpg

Sorry about the URL mess.

I still contend though that because of the relatively low price of these
units, it's not worth pursuing repair for any reason other than personal
satisfaction.

That's the current Plan A. $34 plus $10 shipping from east coast, or
$39.95 ex the one local source.

Then I can do a Jeff Liebermann learn-by-destroying job on the
existing wall unit. Wedging a couple of flat-blades into the current
one showed what appeared to be the end of a pcb and clear silicon bog
filling the entire enclosure. There's something in there warranting a
pcb, and enquiring minds (this one at least) feel a need to know.

Indeed, indeed. But just as I discovered when going through a similar
procedure with a top-of-the-range Philips shaver in which the batteries had
leaked (gotta love the old NiCd technology!), you'll likely find that the
sum of the parts is worth a tenth of what they want for it.

--
Bob Milutinovic
Cognicom

 

[Leif Neland]

Fřlgende er skrevet af Bob Milutinovic:

Indeed, indeed. But just as I discovered when going through a similar
procedure with a top-of-the-range Philips shaver in which the batteries had
leaked (gotta love the old NiCd technology!), you'll likely find that the sum
of the parts is worth a tenth of what they want for it.

But all the people who test-shaved the guineapigs have to get paid too.

--
Husk křrelys bagpĺ, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

 

[pedro]

On Fri, 13 Dec 2013 18:20:25 +0800, pedro <me@privacy.net> wrote:

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive
coupling arrangement to charge the toothbrush battery. Right now
SWMBO's unit isn't charging and I'm tasked with fixing it. Does
anyone know if this operates at line frequency or something higher?
(That will help sensing the field from the charging base to verify it
is operational before I disassemble the toothbrush itself.)

The techo guy at the authorised Braun service centre tested my charger
and confirmed it was dead as, so I purchased a replacement. He also
asserted that they do not contain any smarts, and operate at line
frequency.

For the benefit of others who may find themselves in this position,
the charger coil is driven at 72kHz unloaded, and this rises to 76kHz
when charging the toothbrush. So much for line frequency!

When I get a round tuit I may attack the dead unit with the trusty
Dremel to see what exactly is inside.

Thanks for all comments/suggestions.

 

[pedro]

On Tue, 17 Dec 2013 17:00:20 +1100, "Bob Milutinovic"
<cognicom@gmail.com> wrote:

"pedro" <me@privacy.net> wrote in message
news:tsava9dr83kaa9l606m2p4bp7felk85i3p@4ax.com...
On Mon, 16 Dec 2013 18:47:33 +1100, "Bob Milutinovic"
cognicom@gmail.com> wrote:

This morning I had a look at my daughter's newer unit, which has a
slightly
wedge-shaped oval as the docking point, and that seems to have
considerably
more bulk to the base unit - about an inch tall - which may likely house
additional electronics.

The one we have is like this (but with Oz-pins of course ...):

http://www.service.braun.com/product/big_img.asp?artGrp=3731&partno=0067040173&l=GB&c=AU&pic=parts|xl|67040173_xl.jpg


Well that's an entirely different kettle of fish; the ones I've seen have
the male mating on the base.

This is my daughter's charging base looks like; mine was similar but much
thinner -
http://www.thepartsbiz.com/assets/images/84848387b.jpg

SWMBO's previous one(s) were like that style.

I still contend though that because of the relatively low price of these
units, it's not worth pursuing repair for any reason other than personal
satisfaction.

That's the current Plan A. $34 plus $10 shipping from east coast, or
$39.95 ex the one local source.

Then I can do a Jeff Liebermann learn-by-destroying job on the
existing wall unit. Wedging a couple of flat-blades into the current
one showed what appeared to be the end of a pcb and clear silicon bog
filling the entire enclosure. There's something in there warranting a
pcb, and enquiring minds (this one at least) feel a need to know.

Indeed, indeed. But just as I discovered when going through a similar
procedure with a top-of-the-range Philips shaver in which the batteries had
leaked (gotta love the old NiCd technology!), you'll likely find that the
sum of the parts is worth a tenth of what they want for it.

If they can sell it in Oz for $34 then its probably $2 tops to the
Chinese factory. That may buy all the parts (labour being
inconsequential there, a bowl of rice per week) in their market but
isn't going to dent the parts list here.

Opening is for learning only. Not sure what I will find - electronics
failed or the coil O/C.

 

On Friday, December 13, 2013 5:20:25 AM UTC-5, pedro wrote:

The Braun Triumph 3738 toothbrush and 3731 charger use an inductive

coupling arrangement to charge the toothbrush battery. Right now

SWMBO's unit isn't charging and I'm tasked with fixing it. Does

anyone know if this operates at line frequency or something higher?

(That will help sensing the field from the charging base to verify it

is operational before I disassemble the toothbrush itself.)

I have has some degree of luck with opening some sealed power supplies by putting them in the vise sort of crooked and slowly cranking the vise. Most of the time they'll eventually "pop" and crack open along the sealed halves.. Be careful with this as they sometimes pop with a lot of force. I've never tried this on a toothbrush base though. I'm sure they must be sealed a lot better than a power supply. But if you're "learning by destroying" then you have nothing to lose. Lenny