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My Inventum MK750 milk frother is dead, how to repair?

Background

I have an Inventum MK750 milk frother. It's one that has a base with the power supply and electronics, and a detachable top, to pour the milk in. When the top-cup is put on the base, it presses a switch so the base knows the top-cup is placed on the base.

Problem

The device is dead. Normally the LED's in the buttons on the side light up, but they don't. There is no response when pushing the buttons on the side ~(one for warm and one for cold frothing). And also no response when the top-cup is being placed on the base, and presses the detection switch.

What I tried already

  • I checked the PCB, components, connectors and switches for corrosion. There was just a little bit, but when removed the frother was still dead.
  • I used a multi meter to check if there is 230V coming in = OK.
  • There are 2 fuses, one just after the 230v coming in going to one point of the heating element, and the other coming from the relay to the other point of the heating element. Both fuses measured for continuity = OK.
  • On the heating element I measured the resistance. It is 90 Ohm. (I don’t know what it should be)
  • Since I read that with a lot of milk frothers the relay can go bad, I ordered a new one and replaced it. Result = still dead.

Question

What can I still try or do?

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Hi Ernst,

Is the detection switch actually switching? 9 out of 10 times it's the mechanical components that fail.

Have you checked the fuses outside their circuit? You may be measuring continuity of the rest of the circuit instead of the fuse.

The heating element resistance seems OK.

Other than that I cannot help you further: this frother is a different concept from the one I repaired, which had the heating element and motor in the removable 'cup'.

Good luck.

door

Thnx Cees!

- Detection switch > I measured continuity while pressing the detection switch. Result = OK.

- Fuses: both fuses are separate from the circuitry. So measuring them is measuring clean on the fuses only. I assume they must be OK.

- Heating element: thanks for confirming.

door

Thnx Alan!

Checking the PCB I have found 5 elco's.

I have measured their voltage with power to the board, and the detection switch switched on. You can find the measurements in the attached picture.

In the upper left corner there are two same type capacitors (4.7uF/400v). One reads 1v and the other one reads '-1' in the display of my multimeter.

# Could that be the broken one?

# What do you think?

[image|3183815]

door

Hi Cees,

I have posted some updates. I would appreciate if you could have a look and share an advice if you have any.

Thnx,

Ernst

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It may be the polyester capacitor the does the voltage drop for powering the electronics. There will be a 10-100uF, 25-50 capacitor somewhere. Check to see if there is a voltage across it. If not check or replace the polyester capacitor.

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Hi Alan,

I have posted some updates. I would appreciate if you could have a look and share an advice if you have any.

Thnx,

Ernst

door

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Thnx Alan!

Checking the PCB I have found 5 elco's.

I have measured their voltage with power to the board, and the detection switch switched on. You can find the measurements in the attached picture.

In the upper left corner there are two same type capacitors (4.7uF/400v). One reads 6v and the other one reads 315v on the multimeter.

Question

  • What do you think?

Block Image

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In the meantime, I have replaced most of the capacitors.

On the main PCB:

  • 2x 4.7uF / 400v
  • 1x 10uF / 50v
  • 1x 100uF / 16v

The 470uF / 25v has not been replaced, as I did not have that one available.

On the button PCB:

  • 1x 100uF / 16v

Result:

Unfortunately no difference. Still no response to powering up, no LED activity.

Consideration:

Since there is no information available, especially not about the PCB/schematics, it's a bit of guessing. So far I have replaced the relay, and most capacitors. But with no result. Both fuses measure continuity, all switches work and the heating element also seems ok.

Checking the components on both PCB's visually, there are none that show damage or any other look than normal.

What's left are transistors and IC's.

Question:

Any advice on my next step?

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KolfMAKER zal eeuwig dankbaar zijn.
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