Cordless kettle repair

[cigmas]

It's not exactly an electronics issue, although this cordless kettle does have some electronics and a display and buttons on the handle for showing and setting the desired temperature. The kettle seems to get no power when it is put on its base and its display doesn't turn on, which makes the whole thing unusable. I believe the issue is with the control switch in the base not making contact, but I'm not sure of how the design is meant to work and thus how to fix it safely.

The control switch is a Strix U1762 but I have not found details of its functionality: https://strix.com/component/u17-series/

Here's what the bottom of the kettle looks like:



There are two flexible "wings" with magnets which make contact with the brass-colored flat lead below them which then power the blue and red wires. The wing on the right, which is a bit discolored, is not making contact, as seen below:




The left wing is horizontal and its magnet is making full contact, but the right wing is going at an angle (up in the picture, but down when normally oriented) and not in contact. I don't know if this is by design or if the right wing has been bent out of position somehow.

The reason for magnetic instead of permanent contacts is part of the safety design. Seen in the image below, there are two bimetallic thermostats which contact the bottom of the kettle (note the white thermal grease) which can pop and press against white piston rods, which then push against the wings and detach their magnetic contacts:



I think those are just safeties to avoid running the kettle dry, because in normal operation the display in the handle is still powered to show the temperature even after the water boils and the kettle stops heating. But I'm not 100% sure.

There is also a mechanism whose functioning and purpose I don't understand. There is a pivoting panel which potentially could push the right wing to make contact, but I don't know if it is broken or how it's supposed to work.




There is a pin which gets depressed when the kettle sits on the base. That pin pushes a spring-loaded "blocking arm" out of the way, which seems to be positioned at a point to prevent a panel from pivoting when the pin is not depressed. The pivoting panel has a slight lip (possibly with part of it broken off, but hard to tell) which barely touches the end of the right wing, and can push it just enough to have it make contact, but I really have to pivot it all the way. There is a bulk on the opposite side of the panel which might be a counterweight, as there is no spring. Keep in mind, that the mechanism is normally upside down compared to the orientation in the pictures.

I thought about making a permanent contact with the right wing, but that would lose some of the safety, and maybe also interfere with the normal operation. Or I thought I could add some material at the "lip" to help it push the wing into contact better, in case that part was broken, but I don't understand what is supposed to compel the pivoting, whether the "counterweight" which seems insufficient, or whether there is supposed to be a spring that got lost, or if the spring loaded arm is supposed to be hooked onto part of that mechanism. I don't know.

Does anyone know how this device is supposed to work? Suggestions on how to fix it safely?

[fzabkar]

It does look like a broken "lip" to me. Have you tried searching through patents documents?

[cigmas]

It does look like a broken "lip" to me. Have you tried searching through patents documents?

Interesting suggestion. I now looked up the patents listed in the footer of the Strix webpage (Granted US Patents – US8454826, US7783176, US9259113, US9723947 and US9404649) but none correspond to the control switch, though it is stamped "patented". I'm not familiar with searching patents, but I'll keep looking. This is a good idea if the description from the inventors can be found.

[cigmas]

Apparently the "lip" is not broken. In comparison, here is a new unit:




I just used long-nose pliers to slightly bend the "wing" of the old kettle to make contact, and now it works. I still have no idea of the purpose of the pivoting contraption.

[nightfire]

That lip is the bimetal component that switches of the current when the water is finally hot. That color on that single lip suggests severe overheating at one point.
As those things are also safety-related, problems at that point should be taken seriously...

Usually there is a thermofuse embedded in some lead, that will finally silence that kettle when those metal lips fail. If such a fuse is not present, such a repaired kettle should be operated very cautiously (meaning: Do not go away while its boiling and forget it...)

[cigmas]

The so-called lip is plastic. In the first post I showed where the two bi-metallic thermostats are.

I don't know if there is a thermal fuse in addition to those two, but if there is, clearly it did not trip. The mechanism in the bottom of the kettle is entirely mechanical. All electronics are in the handle with the LCD which I did not open.

The discoloration did cause me some concern. I wonder if poor contact before it finally failed caused excessive heating. Or if there is another problem...

[Hornethandler]

I have the same kettle. Have you verified good electrical contact from the two brushes in the kettle to the ring contacts in the base? The kettle’s contacts become weak over time and need to be retensioned. The kettle is about 10 years old and I’ve had to do it twice in the last 3 years.  Again, the base contacts are fine, it’s the two spring contacts in the kettle itself.

[cigmas]

Have you verified good electrical contact from the two brushes in the kettle to the ring contacts in the base? The kettle’s contacts become weak over time and need to be retensioned. The kettle is about 10 years old and I’ve had to do it twice in the last 3 years.  Again, the base contacts are fine, it’s the two spring contacts in the kettle itself.

What do you mean by the brushes in the kettle, and the two spring contacts? How did you retention?

I think there are possibly a few weak contact points. In addition to what I called the "wing" whose magnet was not touching the contact below it, the springy contact for the center pin (neutral wire) in the base (not bottom of kettle) needed to be bent up a little to touch the kettle's center pin. Also, the metal of that contact has similar discoloration to the right "wing".

Also, I wonder about the contact between the "wings" and the ring contacts in the bottom of the kettle, but assembly does not disassemble further for better examination.

I wish I knew the terms for these components so it would make descriptions easier to communicate.

Btw, the company sent a new kettle under the 3 year warranty. Instead of throwing the old one away, I would rather keep it for a spare if the repair is safe. So far it seems ok.

[Hornethandler]

Please forgive. I should have looked closer at your pics. There are similarities between our kettles, but they're not the same. Sorry for jumping the gun and good luck with finding a fix.