Repair of Bosch induction cooktop touch controls

[cozza]

At home our Bosch induction cooktop became unresponsive to the power on button, in the last week of it's two year warranty. Fortunately I was able to arrange to be there when the repairman came, and replacement of the display / touch panel solved the immediate problem.

It's not an uncommon fault for one or more of the buttons to stop working or be intermittent in operation, according to the repair person. I asked if I could keep the old board to have a look at it, which was fine, because "no one can fix those mate!"   

The board is fairly involved and has touch pads, the led displays, a control microcontroller and a sounder. It is made by EGO, and apparently is common to a whole swathe of other European brands, including Gaggenau, Neff, and possibly Smeg as well.

Inspection revealed that the touch pads connect via a resistor into the inputs of HC4053 chips, a triple 2 channel analog multiplexer. There is no external protection for ESD for the conductive pads which sit below the glass cook surface, although the HC4053 has protection internally.

Replacement of the 74HC4053 associated with the power switch restored functionality, so now we have a service spare board should the fault arise again. I also replaced the HC4053 IC associated with element selection, as this had been unreliable for most of the life of the appliance, although not annoying enough to warrant a service callout.

Hopefully this will be of help to other EE's in an out of warranty predicament.

[chris_leyson]

It's not an uncommon fault, for one or more of the buttons to stop working or be intermittent in operation, according to the repair person.

not at all surprised because it's designed by engineers who don't give a damn. Well maybe the engineers do give a damn but they have to design to minimum manufacturing cost and not for performance and long term reliability...

[cozza]

I'm dreading the day I have to pull out the Bosch wall oven to investigate the similarly (mostly) unresponsive touch controls on that..

It's now out of warranty.

[cozza]

As a non warranty replacement of this control board will set you back over $700 NZD, it's compelling to change the $0.88 NZD chip instead.

Farnell / Element14 2445306

[james_s]

Maybe contact some service shops and offer to purchase defective boards. If new ones are that expensive you can sell refurbished boards on ebay for a tidy profit.

[Pasa001]

Thank you Soo much for posting this. I purchased a Bosch induction cooktop from Europe and brought it back to my home in Hong Kong. The cooktop work fine for two years and now is exhibiting the same unresponsive touch control on/off function (very intermittent). I contacted Bosch repair in Hong Kong but seeing that I imported the appliance they will not service it. I noticed you posted some pictures of the touch control panel, may I ask a huge favor? Could I ask if you would be Soo kind as to take a close-up of the components your replaced? While I'm not an electrical engineer I'm pretty good with a soldering iron and I'd like to attempt the same repair. Thank you so much. Conversely if you offer a repair service I would be happy to post you the touch panel for the repair.

[cozza]

Hi Pasa001,

Assuming you have the same board with the same fault, here's what I would do :

If you look at the 4th image of the board, the HC4053 component replaced is the small black square with 16 pins (8 per side). From the part number and link in the thread you can look up the part (it is a TSSOP package on my board) and either source from farnell / element 14 or locally. Look at it with a magnifying glass - it will have 4053 written on the part if it is the same.

The power touch pad HC4053 chip is the one located close to the power on / off sensor pad, you will be able to see a circuit board connection from the touchpad to a SMD resistor, then onto one of the pins on the chip. Once you've confirmed which chip is controlled by that power pad, you could get an electronic service company to replace it for you, one with experience in phone laptop board repair would have the necessary skills - it is not an easy solder job.

Due to all the surrounding plastic parts which are heat staked through the pcb, (and the board is double sided, both sides have components on)  hot air rework is not the best option. I used flux and a soldering iron to bridge 8 pins on one side of the chip, then heated them all up together while lifting one side of the package off the board very slightly with tweezers, then alternated heating side to side to get the chip off (you have to be very careful not to tear the pads off the board)

Then when the chip is off, clean the board with desoldering braid then isopropyl alcohol before soldering the replacement chip. Note the chip orientation (it must go back the same way around) before you remove it with a photo. I used the tip, flux and drag solder technique.

If you take the board in for repair, put it in an anti static bag or wrap it in tinfoil (in a pinch) for transport.

I'm not able to offer a repair service personally for this type of repair, sorry, but I hope this helps.

[cozza]

On my board, the chip is located directly underneath the on / off button, which is the gray square with no symbol on it.

[cozza]

@ James_s , thanks, but I'm not interested in taking on the liability.

These induction cooktops can be wired in either one two, or three phase configurations, there's no way that anybody inexperienced should be taking the top glass off unless they are suitably qualified to do so safely.

The supply must be turned off at the switchboard.

[Pasa001]

Thank you Cozza! , I'm very careful  and I'll definitely switch the corresponding breaker off, I've yet to remove the circuit board , with all the things going on with the Corrona virus I plan to return home to Canada for a month and possibly try to source the components I need there. I'll post updates when I proceed with the repair in the hopes it helps others. From what I've read many of these Bosch cooktops have the same problem.

[Pasa001]

Well thanks to Cozza I've ordered the correct components and I've now disassembled the cooktop and removed the touch circuit board. Wow I didn't realize how tiny the components are so I'm afraid I'll have to find a competent repair facility to carry out the repair. It's definitely beyond my soldering ability! I'll source a new board for the time being and get this one repaired for the future. I'm really disappointed at Bosch , with the amount I spent on this cooktop it should last more than 3 years, I'll post again once I get the board repaired and update anyone that might be interested. Thank you so much Cozza you are a champ and I'd be lost without your help.

[Pasa001]

Picture of the board

[Pasa001]

Sorry I'm new at posting

[Pasa001]

Last one

[rvalente]

Thats why I use a gas stove, not much to break other than a igniter coil.

[cozza]

That looks to be the same series of board, from a larger cooktop. I'd try getting it fixed before ordering a new one though.. there must be a good surface mount rework place somewhere nearby in Hong Kong?

As the metal strips on the end of the cook surface are grounded, I've gotten into the habit of touching the trim before touching the controls to dissipate any body charge to avoid a repeat failure 

If I was in your city I'd take you up on that beer,  after changing the chips!

[Pasa001]

Repairs have been completed. I took the board to a cellular phone repair facility in Vancouver British Columbia and explained to them what I needed repaired. They unsoldered and resoldered two  HC4053 chips on the board completed the work for 100.00 Canadian dollars. I'm not returning back to Hong Kong until mid April so I won't know until then if the repair was successful. I'll post again once I reinstalled the board into the induction cooktop. I added a picture of the two chips that were replaced. 

[Pasa001]

Last one

[thm_w]

It's not an uncommon fault, for one or more of the buttons to stop working or be intermittent in operation, according to the repair person.

not at all surprised because it's designed by engineers who don't give a damn. Well maybe the engineers do give a damn but they have to design to minimum manufacturing cost and not for performance and long term reliability...

I agree with the second point, very few people care about long term reliability. But your first point is a bit off base.
This is a four layer board, its not "no expense spared" but its very clearly not the cheapest design that could be made. Look in an average microwave oven and you'll see a single layer board with no-name components.

[ClausRye]

I found this article very interesting even though it is a little bit old.

I have the same board not being able to turn on the power.

After removing the glass top-lid I found the power touch-sensor still working (touching it directly) making it possible to turn on the device and test-operate the the other touch-sensors directly without the top-lid.
With the device turned on, I have tried to mount the lid hoping to test/operate the cooktop. Unfortunately I am too slow as it turns off automatically after 10-15 secs...  So I can not tell if the other sensors are working with lid on.

My questions are:
- Can a defective 74HC4053 still work with reduced sensitivity or is my missing/reduced sensitivity caused by another issue?
- Is there a way to measure the good and bad ones with a multimeter?

[srb1954]

I suspect that it is not just engineers that don't care about the design but also penny-pinching managers who insist on protection features be removed or components down sized to save a few cents.

I have had multiple problems with my Bosch induction cook-top due to under-rated components failing. Example: the reservoir capacitors on the main DC bus, which carry the full high-frequency ripple current from the element drivers, melted due to excessive self-heating from this ripple current. The original caps were polyester dielectric; far too lossy for use in this application. I replaced these with polyproplyene caps and there were no further over-heating problems. This was not so easy as the polypropylene caps were 3x the size of the polyester caps and I had to cut openings in the metal case for them to protrude through.

[cozza]

"My questions are:
- Can a defective 74HC4053 still work with reduced sensitivity or is my missing/reduced sensitivity caused by another issue? 
- Is there a way to measure the good and bad ones with a multimeter? "

1 ) Yes, they can still work but be functionally impaired when damaged - one of the element selector buttons on my hob was like this. Weak and intermittent touch response.

2 ) No, not really.

[cozza]

It's worth checking the mounting of the touch control panel, that it is as close to the glass panel as possible. I can't remember the mounting arrangement but some have the touch controls slightly sprung upwards on mounts to contact the glass.

[Domini380]

Hi Cozza, thank you very much for the informative posting. It saved me a lot of time with the repair of similar touch panel. Let me add some comment that hopefully will save time of other people. In the past EGO used conductive rubber foam with a resistance around 100kohm that usually worked reliably and if failed then completely. The foam pads were glued to the PCB on the complete surface. The newer construction uses frame of conductive black plasic with transparent window and the whole element is covered with gray polymer. It is probably conductive but not measurable with simple measurement. They have patent on this where the construction is well described. The problem and design fail there is that only two diagonal corners are somehow attached to the board (probably thermal compression or conductive glue) and two more white non-conductive pins are just inserted in guiding hole. The top surface of the sensors is contacting transparent silicon compound to the ceramic plate surface (Ceran) and glues to this surfaces with the time. The thermal expansion of the ceramic and the board are different and the lateral forces will cause the sensor element contacts to break with the time. Unfortunately the new sensors are stiff enough not to relax the mechanical forces as the rubber foam was doing and the silicon layer too thin for this purpose as well. I experienced also that for each mounting and removal of the ceramic plate deteriorated the function of the sensors. With removed plate all sensors were working but some required some pressure that confirms together with deterioration after each plate removals  the hypothesis for bad contact. The solution was to attach conducting EMI copper foil stripes on all top sensor surfaces (just keeping the LED window exposed). There is 4.7k resistors providing some ESD protection. The stripes a left just long enough on the resistor side to be able to solder to it as the contact pads for the sensor are not exposed enough to be soldered. This solved the problem completely. I believe in your case the replacement of the 4053 the problem was solved not by the replacement of the IC but by the heating of the PCB. The multiplexer is just on the backside of the ON button and the resoldering heated up the contact to the sensor and probably melted the contact just enough to be restored. Probably it will fail again after some thermal cycling but it takes 2-3 years.

[Sascha]

Can you please better explain or take a photo how you soldered EMI copper foil stripes.
Thank you in advance.

[scooch]

Hi Domini380.

Also having the same issues with several buttons.  Domini380 can you please post a picture of these copper strips and how attached?
I have been researching this issue for over a year and this seems to make sense!  Thank you.

[cozza]

Hi Domini380,

Thanks for figuring out how the EGO touch system works and what to do when it fails.. that all makes sense now.

The Bosch wall oven has now developed an annoying fault, where once or twice a month it will randomly turn itself off while cooking - no fault code is shown, it just plays the turn off tune and shuts down. Fortunately I'm normally within earshot and hear it abort, but it could end up being a very late meal otherwise! 

There's something to be said for mechanical switches and simmerstats after all.

[benneton]

I will put my 2 cents, if you don't mind. Had similar issue with my De Dietrich induction plate.

What I discovered too that touch panel is responsive with direct capacity change with a simple touch of screwdriver on it. I suspected that either some passive components are weared-off or that glass would have some issue. Tried with some glass that I had from some older plate - it worked. So my conclusion was that there's some issue with the original one's coating from the inside and I was right. I just taped some insulation tape from the inside to separate the touch areas. Worked well after that. My guess it heat damaged it somehow (maybe near placed or too big cookware?). This works for 3 years now (my concern was it won't last due  to simple insulation tape that I've used - thought it would peel-off - it didn't obviously).

For the other Sauter's cooktop, I had similiar issues but that time it was due to some faulty filter caps on the power board. Power supply from the power board to touch panel had some unwanted signals on the 5v and 12v. Maybe it affected multiplexer/mcu work somehow.

Hope this helps.

[digicur]

Hi Benneton,

could you please give us more details about your solution to this touch control issue? You applied small pieces of insulation tape on the back of the glass plate in order to separate each single touch area from the other touch areas? Is that correct?

Thank you
Phil

[benneton]

Hi Phil,

Yes, that's correct. It seems like existing coating "expired".

Sorry for the late reply!

Regards!

P.S. Could be that coating became conductive. Can't imagine any other explanation currently...

The indications that were present on De Dietrich's hob before I applied the tape solution (without particular order):

* Not responsive
* Multiple key pressed error (dashes blinking on the display and beeping)
* Turn off seconds apart from the power on pressed

[Klimfilt]

Hi all, unfortunately i'm writting here with the same problem... I have Bosch PXE675DC1E and first the timer button started to make troubles, but i ignored it because it's not a important key, but now the power button is dead and now this is a big problem. Im out of warranty so when i went to official bosch repair service, they told me that they don't service PCB and when client came to them with problem like this, they just buy new PCB... Yeah, 150 euros per 2 years, and after 7 years i will be paid the same amount of the induction hob, but this time will be only in boards... It's ridiculous and pity for Bosch company...

So now, how to resolve the problem. I saw 3 different methods to resolve problem. 1) to change the 74HC4053 chip , which accordingly to cell phone service technig would not help, because either the chip is working or not (i saw the post by Cozza) but if i tell him to do, he will do it after all. 2) to add copper foil on buttons (sensors) after i remove the glass, like Domini380 did and 3) to use isulation tape and put it on the back ot the glass, between sensors and glass, like Benneton sugest. So 2) and 3) method are close by same way, because both give advantage to increase touching surface and to make it more solid. Today we opened the hob and without the glas we touched the sensors directley and they worked, after that we used different cover for sensors (simple thin glass) and it worked just fine. But there is a logic in that, the chips to be gone because of the heat. And last one, guys from official Bosch service gave me 3 boards for free with buttons (sensors) and chips. I'm not sure that they are from the exact same hob, but visually they are the same (some have 2 large zons, other have more buttons) but in general they are the same.
So is it a good idea to use other HC4053 chips (not the one behind power button) and to install them on my board, or to order new ones from Farnell ? And will this even work, i mean to change chips?
Or to try to make touching area stronger?

P.S. Benneton do you have pics of your work ? And if not, can you tell where exacly did you put isulation tape on the back of the glass? Where the sensors make contact with the glass (looking my glass on the back, the sensors made their own nests), you mean to add tape there or ? I would be very greatfull if you add 1-2 pics of your job.

[benneton]

Hi @Klimfilt.

Insulation is not above the sensors, but surrounding the spots. Just follow the pattern that was already there. I did take a picture from above (moment ago) and remembered that I also removed remains of old coating, too. See attached.

Will see to open it and make some pictures from the inside.

[cozza]

Hi I would follow the advice of Domini380, as it's specific to the type of controller fitted to your cooktop. I cannot say whether the advice regarding adding the layer of insulation is relevant as it is a different type of hob.

I would try adding the copper foil strips to the non responsive buttons first and see if that solves the problem. If nothing improves, then replace the 4053 chip associated with the button. The copper strip on the button would connect via a piece of thin wire to the 4k7 resistor which feed into the 4053 input.

Let us know how you get on, I am curious.

[cozza]

The problem with the Bosch touch sensors as Domini380 explained it is the connection between the grey conductive stuff on the button, which connects through a heat stake to a PCB pad, to the 4k7 resistor getting weak due to thermal cycling.

The easiest button to verify this with is the power button (no illuminated legend to cut around). Cut a square of foil the size of the top of the button (and leave attached a thin strip of copper foil like a wire to connect to the resistor).

Glue the square to the power button, solder the thin strip of foil to the 4k7 resistor ( the button side, not the chip side) and see if that solves the problem.

[Klimfilt]

Hi all and thanks for fast responses. I'm sorry, but i'm not good at electronics (i'm an accountant...) but i like to resolve problems, not to be a consumer guy... So, please forgive me, but i didn't understand all that i should do . I'm attaching pics of my PCB, and what i did today and the how started to work (well not all sensors, but 85% of them are as new). When i removed the glass i noticed that the PCB lay on a black plastic base. This base is hooked to large metal square by 2 pinchs. When i touch the PCB it seemed to be very unstable and shakes a lot. So my first guess was that there is a "big" distance between the sensors and the glass. So i add some pieces of cardboard. After that PCB become a lit a bit stable and i installed the glass and when i tried the power sensor, voala it wokrs just like new one... But unfortunetley my joy was short when i figure out that not all sensors works. With this "invention", sensors marked with "1", "2", "5.5", "9", "boost" and two sensors for the large cook zone don't work. I know this is not a serious job and it's dangerous but it work and it's a some kind of a starting point. I will atach pics of my hob and what i did, but i didn't understand quite good the part with copper foil and where to put it. On top of the sensor (between the glass and surface of the sensor) or to remove the sensor from the PCB and to add it over the PCB and after that to install again the sensor on the PCB ? And what about the wire, and which resistor to connect with it? Sorry once again, i just need to be explained it like for a newbie or even a full noob with electronics. With 2-3 pics of the exactly what it should be done, may be it will be easy to understand. I will be very greatfull.

IMG1 - This is my "working" hob after my "invention".
IMG2 - This is the cover underneath the glass. Im not sure but i've read somewhere that this is some kind of silicium. @Benneton could you please tell me exact where i shoud add insulation. Can you point it on my pic ?
IMG3 - This is what i did...
IMG4 - How it looks after asembly
IMG5 - And it works ... Partly...

P.S. All sensors are working when i barely touch them directly (i mean when the glass is removed, like picture 5)

[Crocodiledundee]

Hi all,

I opened up my induction cooker and found that one of the soft black pads on the touch pad Board has come detached which explains why one of the hobs has no response when trying to turn it on. Can anyone tell me what adhesive I should be using to glue the soft black foam back onto the board? From looking at it it looks like they used 3 dots of some kind of red adhesive. Please kindly advise.

[Klimfilt]

Hi again and thanks for advice. So if i'm undestand it right, i have to put a copper square foil on top of the sensor (button). Second i have to solder a very thin copper strip, the one side to the copper square and the other side of the stripe have to be solder to the one (or two, even both may be?) of the corrners which are underneath the sensor. For this one i have to remove the sensor from PCB and solder the thin stripe. Right? Not to the opposite side of the PCB where there is only chips. Am i on a right way ? And if this didn't work, to re-solder the chip ?

[Crocodiledundee]

Hi all,

Update, I used some 3m spray glue which is approved for conductivity and reattached the conductive foam to the chip board. This seemed to have done the job and upon testing with a screw driver as well as a my finger the button worked fine and well. However, when I put the glass panel back on and tried to use the aforementioned button there is no reaction. I checked the conductive gel on the underside of the glass and it is fine without distortion or damage. I am absolutely miffed as to why as soon as the glass panel goes back on the button no longer works. Any ideas what the problem could be?

Ps the cooker has 4 hobs and the faulty button is the button that activate the main/big hob.

[benneton]

Coating became conductive, I have no other explanation. It is what's with my hob. If it is conductive, one sensor is giving electrons (or stealing) from other sensor/s (case with capacitive ssnsors only, not optical). Just add some regular sellotape to check if that is the case. Put the glass back and test it. If that would help, find some fire resistant tape. In my case I have ceramic icons printed on the glass. Since your hob has led icons, I think that my solution with insulation tape wouldn't work because it is not transparent. Like I said, try only with sellotape. If that would be the solution, use something that will not catch fire (or melt). So: sellotape over the glass where sensors are. I cannot fiddle with the disassembly, sorry - all is sealed perfectly with silicone around. But no need actually to do that. Just imagine conductive coating... Add something that is not conductive over it.

[cozza]

Hi sorry for the late response. I'm at home in lock down, the hob controller is at my workshop so I can't confirm the soldering points.

You don't need to remove the sensor pads at all. It will be a case of sticking a strip of copper foil to the top of the "button"  and soldering the other end to the corresponding resistor for each button - on the top side of the board. I'd try a thin (2 or 3 mm) strip first rather than a full square the size of the button.

Start with a thin strip and see if it's sensitive enough.

Note I have not tried this, I'm just going on the previous post.

If you hold the board up to the light you'll see a clear circle of fibreglass with a pad in the middle next to each touch sensor, this is the point where the plastic touch button connects to the circuit board trace / resistor. Looking at the photos it may be a 10K resistor for the power button (103) and 4k7 resistors for the other buttons (472).

Using a multimeter you should get 0 ohms between the pad in the circle and the end of the resistor the foil strip will need to be soldered to.

[ievosabo]

Hi, after reading all this, I decided to fix the cooktop one more time
Short flashback: my previous step was using silver conductive glue to fix the covering of the "gray" sensors. I would say it was not a great success, but at least 90% of sensor buttons were reanimated.
I used a Kapton tape and thin copper wire this time. So, I soldered to every button's resistor the thin copper wire. The wire got the form of a not closed-loop rectangle over the sensors. These tiny "antennas" are covered by Kapton film to keep them intact.
Hence, I have every sensor with an individual wire over it and every sensor isolated from a fiberglass top by Kapton tape. Every button works precisely and has no problem whatsoever. I must test it under thermal stress, using all induction areas simultaneously when cooking a lot.

Thanks for advising the engineers. It looks like you are right. There are two major issues/things: 1. make sure sensors are appropriately isolated (I used a Kapton tape in my case) 2. improve/fix sensitivity by duplicating a sensor area with an extra copper layer (I used thin wire, as do not have dedicated copper tape recommended above) but it works and the idea the same.

Did nothing with the ICs.

I hope it helps you with the repair work.

[scooch]

Hi.  Thanks so much for the information and hoping to fix our cooktop and we keep losing one button after another.

I think I understand your method but any chance you could post a picture?
It would be greatly appreciated!

[scooch]

Klimfit.  I have the exact same problem and same type of cooktop.  Elevating the control panel helped with some buttons.
It seems that the black silicone substance on the glass may have lost its conductivity and/or shrunk.
Wondering if you ever resolved your issues?  Thanks.

[buhini]

Hi, first of all introduce myself because I'm new to this forum.
 My name is Rafa and I am fond of electronics, my job is a vehicle mechanic.
The second thing to apologize for the bad translation of google translator, since I do not speak English.
I wanted to show you my experience with my bosch induction hob, the same one shown in this thread.
The same thing happened to me as to the rest of those affected, loss of touch on the buttons, at first I didn't mind losing the 9 or 0, but when the power stopped working I couldn't stand trying to repair it.
My first option before discovering the forum was to resolder the most accessible resistors and capacitors on the entire board, this did not solve anything.
The next thing was to fit the electronic plate with cardboard below to raise the point of contact with the glass, but it didn't work either, it made error sounds.
So I found this forum and read it in its entirety, I ordered the 4053 chips on aliexpress and as soon as they arrived I changed the first one, the one corresponding to the power and lock button, tell you that I noticed a little more touch without the glass, but with the glass on did not work.
So I changed the 4053 chip corresponding to the most affected buttons, the ones that had to be pressed in the lower corner to be activated, in my case it was number 9, I put a new chip and before trying it I decided to resolve it with quality flux and Tin the rest of the 4053 chips, all of the ones on the back plate (be careful! Only resolder).
And it turned out positive! All the buttons on the panel revived like the first day with the glass on.
I have cooked and everything is correct, but I realized that suddenly the 0 button had failed again together with the 9 button, and the turn on button again becomes less sensitive and you have to press it a little harder, so I will disassemble again again and I will change the 4053 chip that affects those buttons and I will try again.
So I recommend not putting cardboard under the plate, since the problem is electronic and not due to the silicone of the glass.


Hola, lo primero presentarme porque soy nuevo en este foro.
 Me llamo Rafa y soy aficionado a la electronica, mi trabajo es mecanico de vehiculos.
Lo segundo pedir perdon por la mala traduccion de google traductor, ya que no hablo ingles.
Queria enseñarles mi expereciencia con mi placa de induccion bosch, la misma que se muestra en este hilo.
Me ha ocurrido lo mismo que al resto de los afectados, perdida de tacto en los botones, al principio no me importaba perder el 9, o el 0, pero cuando dejo de funcionar el power ya no pude aguantar a intentar repararla.
Mi primera opcion antes de descubrir el foro fue resoldar las resistencias y condensadores mas accesibles de toda la placa, esto no soluciono nada.
Lo siguiente fue calzar con carton por debajo la placa electronica para elevar el punto de contacto con el cristal, pero tampoco funcionaba, emitia sonidos de error.
Asi que encontre este foro y lo lei entero, pedi los chips  4053 en aliexpress y en cuanto llegaron  cambie el primero, el correspondiente al boton de encender y bloqueo, deciros que note un poco mas de tacto sin el cristal, pero con el cristal puesto no funcionaba.
Asi que cambie el chip 4053 correspondiente a los botones mas afectados, los que tenia que apretar la esquina inferior para ser activados, en mi caso era el numero 9, puse un chip nuevo y antes de probarlo me decidi a resoldar con flux de calidad y estaño el resto de chips 4053, todos los de la placa trasera (ojo!!, solo resoldar).
Y resulto positivo!!, todos los botones de la placa resucitaron como el primer dia  con el cristal puesto.
He cocinado y todo correcto, pero me di cuenta que de repente el boton 0 habia vuelto a fallar junto al boton 9, y el boton de encender de nuevo vuelve a ser menos sensible y hay que apretarlo un poco mas fuerte, asi que desmontare de nuevo y volvere a cambiar el chip 4053 que afecta a esos botones y volvere a probar.
Asi que recomiendo no poner carton debajo de la placa, ya que el problema es electronico y no por la silicona del cristal.

[buhini]

In the end I decided to change the control panel because I repaired the contact buttons three times by changing the chips, and it lasted working well for a couple of hours, then they failed again, I bought the control panel directly from Bosch, 179 euros, and it works perfectly, they have modified some things and removed others.

[Otso]

Thank you ievosabo and everybody! With your aid I was able to fix this on my hob.

I've only tried the 7, which was broken, and it now works perfectly! I'll go on and the the same for the remaining failing buttons (about 4 more).

I took a strand from multistranded ethernet cable and soldered it to the back where the button is attached. I also tried soldering to the resistor, but this one was too difficult for me to reach, and I managed to melt the button slightly when I tried.

Beware though, that you might mistakenly pull out the original solder for the pad, which I did at least partially. I first tried soldering a thicker wire, from a single stranded ehternet cable. It was too thick and heavy, and difficult to attach, and I managed to pull out the solder with that one.

Here's pictures of the front and back.

[Otso]

I ended up repairing 9 buttons. Now it's good as new again! Thank you once for the advice. I would never had figured out this myself. And no components needed to be replaced.

In case anyone is wondering which resistor to attach to, it's the tiny resistors next to the button. As has been said in the thread, to make sure your are connecting to the correct resistor on the correct side, measure that the resistance is close to 0 Ohm between the resistor and the tiny pad on the back to which the button is connected.

Here's a photo showing some of the resistors encircled with red, and also showing one of the buttons I fixed.

[ELBUTMAN]

Hi all, I could also repair my faulty touch button using the suggestions from Domini380. In my case I could solder the copper foil directly to the metal circle in the board on the base of the button, that wasn't completely covered by the pad in the edges. It works perfectly now!  Thanks again!

MAC

[optic]

Just repaired with your help. Only thin wire, without tape. Soldered from bottom, much easier. Pictures attached.

[Swake]

Another win!
Given the number of cooktops that fail this clearly falls in the category of the manufacturing issues.

[francesco.comi]

First I would like to thank you, Otso and everybody else who helped identify and solve this issue.

I have the same issue with a Siemens cooking top with very similar controls, with a recently replaced glass.
After the glass replacement new buttons started to stop working.

I'm planning to do the same fix, but I have a couple of questions of how to exactly do the fix.

If I understand correctly I need a small wire (I have plenty) and I need to create a loop, put it on top of the touch button and solder it on one of the ends of the nearby resistor.

My questions:
- should I solder only one end of the loop?
- should the loop cross (I meed the two ends of the loop should touch at the end of the loop)?

Maybe I'm missing how the fix works...

I'm very practical with soldering, but never worked on this kind of touch controls.

Thank you for any help.

[francesco.comi]

I finally tried e succeded!

I would like to thank everyone who helped finding a solution to this issue!!!

I did the thin wire solution, it worked perfectly at the first try on every button I did it!
I used simple scotch tape to keep the wire attached to the button and isolated.
For some buttons I soldered near the resistor, on some other buttons it was too difficult to reach and used the via in the bottom. (Pictures attached for the first two I did)

For anybody with this issue, go ahead and do it, it is easier that what is seems!

Thank you!

[Otso]

The buttons have been working for me since I fixed them. However, after some time the cooking top has occasionally started beeping, similar to when you leave something on the top of the buttons. I wonder if they got oversensitive. When this happens, the only fix I have found is to power cycle the cooking top (by switching off the fuses and back). There are slight variations between how it behaves. Some, but not all, of the problems seem to occur when it has been hot for a long time.

[Fron]

Hello all induction repairers...

I read with lots of interest the communication about other Bosch induction cook plate troubles, so I ask your opinion about the following:

My daughter's Bosch induction cooktop (PIA645Q16E, 10 years old)  has different keys, I think infra red sender/receivers, and no problem there... But suddenly it made blew the fuse (house, 3-phase fuse of the cooking stove) and does not work anymore, even with fuse re-activated. I opened the cook-plate and found out 2 of the four IGTB's are defect. No visable damages but I measured them with an OHMmeter and the 2 left ones measure no values, the 2 right ones do..
I consider also exchanging the rectifier as I read this might have an influence too...

If someone can give me additional advice, please do so, as I have absolute no experience in this matter, only general 'mechanics' and all-round technical, mainly cars and medical equipment...

[Whales]

(Take this with a grain of salt, I have not worked on induction cooktops)

The IGBTs blowing might be a symptom, not a cause.  Other components may have worn out, perhaps there is a short in the coils or the capacitors have gone bad.  You might (?) be able to measure some of these problems with a multimeter.

[Fron]

Thanks for your super fast reply!
In the mean time I started to unsolder the defective IGBT's and rectifier, so I took out the main PCB and the back side did not look as 'nice' as the component side... ;-( I'l try to add some pictures.) Apparantly some fuses have blown with intense 'fire'-residues... These fuses (I assume that's what they are) have dissapeared and show empty burned tracks between some flat PCB-surfaces (wide tracks for high currents , I assume). As an unexperienced soldering guy, I don't think I can repair these 'fuses' (?) and even if I could, what is the value? It's a multilayer pcb.
So I think time has come to look for a new cook plate, nowadays available at about 400 euro's, the price Bosch asks for a new main PCB...

If someone can advise me the values of the 'fuses' and how to install them, please let me know. I might consider giving it a try.  On the picture, you can see some burned 'bridges' between the two white coloured rectangular zones. I assume that's where the fuses have burned...

[Whales]

Fron: could you please upload full quality versions of those photos to the forum by attaching them to your post?  Your external host (postimg.cc) only seems to have very small versions of the images, even when I click "Download original image", and I can't quite see the detail on some of the burned spots.  (Also image hosting websites inevitably die, many forum topics have become useless to readers because of this)

> These fuses (I assume that's what they are) have dissapeared and show empty burned tracks between some flat PCB-surfaces

Where do you see burned/disappeared tracks?  Are they the round translucent white rings with missing squares in the middle?  I have circled them in red:



These 3 marks are wired in series are look perfectly identical to one another, so I doubt they are fuses that blew during operation (but I could be wrong).  Perhaps they were factory milled/marked for some reason.  I am unsure of the function of those large rectangular copper shapes.

I can't quite tell yet, but I think most of the marks might be a combination of electrostatically attracted dust (brown) and arcing between exposed parts (black) possibly aided by the dust.

[Fron]

Hey Whales, OK, I put more detailed pictures although you're interpretation is correct. I mean the circeled (in red, by you) zones. The strange thing is that the other side (component side) of the print looks impeccable, as new. So the burn traces are really just on the back side surface of the board. I join the front side picture too. I assume the burns are 'fresh' and not due to dust accumulation by heath over the years. My experience is that such 'dirt' can easily be wiped off. Not on this spots...  It really looks to be caused by 'fire' or 'explosions'. So I assume some burned tracks. The white 'rectangles' are so imprinted on the pcb... Maybe showing the position of 'plates' in between the multi layers of the board?
The two soldering points top left of that rectangles (on the new bigger picture) is the mounting of a varistor on component side. This too looks 'as new' at component side! The location is indicated by an oval and the letters 'VR1'. You can also see the (now) open holes for the (dismounted) rectifier and one of the IGBT's?  So I was quite surprised by looking at the back side as my first impression when inspecting the component side of the pcb was 'notting visibly wrong'.
Quite bizar, that white rectangles, as if indicates the place where some component should be installed, but it is the back side of the pcb, and no 'fallen of' components found... ;-). I think it indicates the location of a 'plate' in between the multiple layers, and those where connected by the burned 'bridges' (?). So I'm afraid it's end of story. Even if I 'd find out the 'value' of what is missing (?) there, how should I solder it? To what connection?

<a href='https://postimg.cc/14VVmcrp' target='_blank'><img src='https://i.postimg.cc/14VVmcrp/Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-06-75fe4518.jpg' border='0' alt='Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-06-75fe4518'/>[/url]

<a href='https://postimg.cc/PPKVQwPF' target='_blank'><img src='https://i.postimg.cc/PPKVQwPF/Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-07-0ed32d04.jpg' border='0' alt='Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-07-0ed32d04'/>[/url]

[Fron]

upload picture

[Whales]

Thankyou for the higher res photos.

Wow those 3 spots are indeed blown traces.  The copper has completely vaporised in 3 locations in series with each other.  There must have been a lot of continual high-voltage and high-frequency arcing.  Possibly the high frequency nature of the AC made it do a really neat and tidy job of milling away the copper?

The white circle are caused by the heat affecting the green soldermask.  I am not sure what caused the different smoke colours (brown & black), perhaps the 1st arc was a different temperature and size, then the others were smaller because of the higher series resistance of having to sustain multiple arcs.

Something is very wrong with your board if it was arcing for this long, eating away 3 different spots in series, all without stopping or complaining.  Possibly the entire high-power LC tank circuit is bad (bad capacitors?) or maybe the IGBTs were being driven too hard (bad sensing?).  I wish I could be of more help, sorry.

[Fron]

<a href='https://postimg.cc/0MzfD1GY' target='_blank'><img src='https://i.postimg.cc/0MzfD1GY/Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-06-75fe4518.jpg' border='0' alt='Afbeelding-van-Whats-App-op-2024-01-08-om-13-54-06-75fe4518'/>[/url]

Yes, quite a remarkeable burn spot, also on the back cover! I assume it must have been a strong 'spark' during the 'explosion'. I was not there when it happened, it is my daughters cooking plate. I think they heared 'a  noise' and the corresponding  fuse blew.
In the mean time it was decided to replace the cooking top by a larger one as the current has the problem of not enough room for several big size cooking pots. I wil (some day...) grind away the material around the burned fuses and see what's underneath. May be I can solder some wires as new 'fuses' (?- what value?) and of course replace the defective IGBT's and rectifier, and also check the capacitors...
Anyhow, thanks for the reactions!

[Fron]