Ankarsrum AKM6230 1500W repair

[Marek85]

I bought a broken Anakrsrum mixer and I wanted to repair it for my wife but I'm stuck. It seems like the motor controller is damaged. I can't find the board on ebay and the only place that offers these boards is a finnish site which will sell this part only to finnish service shops

https://www.huoltopalvelu.com/epages/huoltopalvelu.sf/en_GB/?ObjectPath=/Shops/Huolto/Products/600000018-52

I would be great if anyone would help me to get this board...

As for troubleshooting I can't find any schematics for this board. I made pcbRtg file for this site https://thmq.mysteria.cz/pcbRtg/ If someone wanted to take a look and could help me to reverse enginner it.
1. Switching the mixer ON does nothing. No noises, movements, nothing at all. The PCB and inside of the mixer looks pretty clean no burn marks or cracks.
2. The PCB board is supplied by AC and ATtiny861 on the board is supplied with +5V. But I dont know how to diagnose if it's alive or not.
3. I noticed that the R24 is shorted (no burn marks) and from the color code it should be 27.9 Ohm. Replacing it didnt help.
4. The motor is controlled by BTB16-600BW triac. I dont see any DIAC but I assume that pulses are generated by ATtiny. The motor is fine I checked it with a cheap AC motor controller like this one: https://www.amazon.com/Controller-Electric-Voltage-Regulator-Adjustable/dp/B07GFKMGXR
5. There is a speed sensor that might be damaged aswell. I think it sends the speed signal as a feedback to the PCB. The controller will push more current through the triac when the load increases to maitain stable rpm. But I think even without this sensor the motor should start at least?

Thank you for any help.

[Marek85]

Pretty weird +5 V power supply for ATtiny microcontroller using TL431. But it seem to work just fine.

If someone knows this type of voltage regulator or materials where I could read more about it and learn how it works would be great.

Anyways this seems to be OK in the controller board of the mixer.

[Swake]

This is a capacitive power supply. Not very efficient, but negligible compared to the motor and this device is not switched on all the time anyhow.

Are you sure the triac is still ok?
If that big resistor was the gate resistor then I think that gate is gone.

[Swake]

This guy explains pretty well how to simply test a triac with a multimeter.

[Swake]

Source of the board in Norway. Don't know if they'll sell something to you or not.
https://reservedele.nu/produkter/dele-til-smaaapparater/roeremaskiner/ankarsrum-assistent-dele-og-tilbehoer/print-til-ankarsrum-akm6230-akm6290b~40392

[Marek85]

Thank you Swake,

Source of the board in Norway. Don't know if they'll sell something to you or not.
https://reservedele.nu/produkter/dele-til-smaaapparater/roeremaskiner/ankarsrum-assistent-dele-og-tilbehoer/print-til-ankarsrum-akm6230-akm6290b~40392

I wrote an e-mail to them whether they can send the board to Poland or not.

This is a capacitive power supply. Not very efficient, but negligible compared to the motor and this device is not switched on all the time anyhow.

Are you sure the triac is still ok?
If that big resistor was the gate resistor then I think that gate is gone.

I checked the triac in circuit and seems to be working fine. It responds just like on the video you posted.

That resistor that I replaced is not at the gate but in series to terminal 1 of triac. I doubt now if this should be 27.9 Ohms... Maybe it should be a shunt resistor and I'm missreading the color code in it? I just cant immagine a 28 Ohms in series to a 1500 W motor supply lines.

[Swake]

The value you read from the rings is correct. The picture in the first message shows red purple black, 27 Ohm, the one from the spare parts site is red purple white gold 27,9 Ohm

It could be a fusible resistor. Still, 27 Ohm sounds as a lot. Maybe some wizardry is going on here.

I notice the pcb tracks are very close to each other around that resistor. Are you sure there is no short between any tracks?
You mentioned that the resistor measured as a short. When you have that resistor removed, is the PCB still measuring as a short or is the short gone? And the resistor ones removed was it still reading as a short?

[Marek85]

The first picture shows the board with R24 already replaced by me. The second picture is from the site but it looks the same as the original that I soldered out. The desoldered resistor shows really low value just like a short. After desoldering it from the PCB the short is gone and I can measure the 27 Ohms I soldered in.

But still the configuration bothers me because it is in series to M2 and L.

PS: No answer from the spare part shop yet.

[Swake]

The gray color and roughness of the quoting makes me think of a fusible resistor. But maybe we're wrong and this is not a resistor.

There seems to be a 'wave' in the cylinder indicating this might be a coil. Therefor I think of an inductor, but those have only 4 bands and most of the time come with a light green glossy background color.

[Swake]

Let's probe some signals. I'd start with the gate of the triac to see if it gets triggered or not.

As this thing is in direct connection with mains be careful. Do you have an isolated scope or a scope with a differential probe?
Else I guess the gate signal should be measurable with a multimeter. Some can even measure pulse duty cycle.

[Marek85]

I have a regular oscilloscope with non insulated channels. But I could always connect the GND to the GND of ATtiny861 that is on the board right?

Few days ago I tried supplying +5V rail externally but I didn't observe anything special on the uC or at the triac gate. Only see static +5V signals like I'm measuring some pullups or just plain GND. But the uC can have some safety mechanisms that in case missing AC voltage he will just go into failsafe mode and not trigger anything. It think since there is no DIAC on the board the uC measures the zero-crossing points. For measuring the board under AC I need to prepare some cables and solder in the old R24 (0 Ohm) because I don't want the 27 Ohm to blow up on me

My colleague said that to check if the ATtiny861 works at all I could solder it out and check if I can read signature with a programmer?

PS1: I hope the spare part shop will come back with some good news

PS2: I started also thinking If I can get my hands on some sort of off-the-shelf controller suited for the 1500 W motor that has also the feedback loop circuitry. I think its called the PID controller right?

[tunk]

Probably not your problem:
Recently I repaired a magnetic stirrer where the
trimpot/potentiometer for RPM control was broken.

[Swake]

I have a regular oscilloscope with non insulated channels. But I could always connect the GND to the GND of ATtiny861 that is on the board right?

NO !!

The 'GND' of the scope is connected to the earth in the mains power plug. The 'GND' of the ATtiny is on another potential. So the risk is to blow up the scope and of course to blow up yourself too.
Actually from the schematic in your message #7 the N wire is connected to +5V. So no... don't connect those 2 'grounds'. Same (confusing) name, but 2 different things.

The 5V injection is a good idea. Without mains power of course. You might want to look a bit further to see if that thing is still alive or not.
Trying to read the program in the ATtiny is an interesting path, note that it might be protected.

You would be very lucky finding a controller that matches the input (the sensor) and the output (1500W motor). The control loop can be made of different methods. PID being one of them. Another possibility is to use that 'dimmer' and let your wife turn the knob when it is too slow. That is the simplest loop you can have.

[Marek85]

Probably not your problem:
Recently I repaired a magnetic stirrer where the
trimpot/potentiometer for RPM control was broken.

The RV1 blue potentiometer in circuit behaves very weird. It is a 47k potentiometer and in circuit I measure only weird stuff but when I desoldered it seem to be fine. It measures 41.6k not exactly the 47k but I think good enough and it goes down to about 36 and 44 Ohm depending which side I measure.

[Marek85]

The 5V injection is a good idea. Without mains power of course. You might want to look a bit further to see if that thing is still alive or not.

So I injected 5V into the board and measured around the ATtiny with multimeter since no dynamic (PWM, CLK... etc.) signals are there.
Current consumption is 57 mA.

P01 = 0.3 V
P02 = 0.2 V
P03 = 0.2 V
P04 = 0.0 V
P05 = 5.0 V
P06 = 0.0 V
P07 = 3.5 V*
P08 = 3.5 V
P09 = 0.2 V
P10 = 5.0 V

P11 = 2.5 V
P12 = 2.5 V
P13 = 0.0 V
P14 = 5.0 V
P15 = 5.0 V
P16 = 0.0 V
P17 = 0.3 V
P18 = 0.3 V
P19 = 0.0 V
P20 = 5.0 V

*- PIN7 = XTAL1 toggles only when I connect the probe. When goes to LOW then current drops to 5 mA. It looks like the uC is working (current = 57 mA) but additional capacitance of probe will throw the internal oscillator off balance and uC stops working and current drops to 5 mA.

I also tried to feed a PWM signal to the speed sensor input at PIN14:
PW =  10 ... 90%
50 ... 200 Hz
Upp = 5 V

But no reaction.

[max.wwwang]

That resistor that I replaced is not at the gate but in series to terminal 1 of triac. I doubt now if this should be 27.9 Ohms... Maybe it should be a shunt resistor and I'm missreading the color code in it? I just cant immagine a 28 Ohms in series to a 1500 W motor supply lines.

I concur with your doubt. This fatty boy looks like a current sensing shunt resistor, which, as you said, is normally small Ohms. Check carefully the original one.

[Swake]

No live on the pin that is triggering the gate of the Triac?
That Gate is not shorted to GND or +5 ?

The more pulses from the sensor, the quicker it runs, the shorter the pulses to the triac to reduce it's speed. Inversely as long as there is no signal from the sensor it should think there is no (slow) rotation and the gate should be triggered all the time to give it more power. Of course this cannot last long before the motor burns, but it should at least try for a second or so.