Hersteller: Bosch | Typ-/Modell: Benvenuto TCA6301 - B30 | ca. Baujahr: Unbekannt

Hello all Guys,

I know it is not too kind using english on german forum but I have no other way as don't know german unfortunately. Hope it is not big problem here! Pls forgive me my polish "english"...

I have a problem with grinder in Benvenuto B30. In normal way after pressing the "Cafe" switch is running the water pump and grinder (also with no beans). If there is no beans in the grinder and a powder cannot be made we get communicate "Add beans". My problem is that an engine of grinder is not starting at all and in effect I get "Add Beasn" of course. Grinder is not mechanicaly blocked - dismounted and cleaned. An engine is not fault - I am electronic engineer so have forced getting power on the engine - it's working well. Going back along the wires/circles I have found that from the front controller board is not becoming any signal (voltage) that could switch on the triacs and give 230DC to the engine. What can block the controller? I have checked all the visible sensors, switches - looks ok. Have no more idea. What can I do yet with this?

Mechanische Kentnisse vorhanden: NEIN | Elektrische Kentnisse vorhanden: NEIN | Messgerät vorhanden: NEIN

Hello BlackSheep,

Many thanks for your reply! I spent half of this day checking whatever is suspected there...
Do you mean these Microshalters that I have found on the Forum?
kaffeemaschinen-forum.de/index…787a1f8a9e190277a9011cfc7

I have checked them already and both are working properly if we say about their switching. But I am not sure their positioning. When the Machine is ready to be requested for coffe the left switch is opened and the right one is closed. Is it normal? I am asking because if the controlling ring would be rotadet left just 1-2 deg then both are opened. But it require to use a force smelling like breaking some plastics inside...

I have already opened the box with controller. It doesn't like to me. In the same way Processor is controlling 3 optiotriacs using three outputs, one is for grinder and two I don't know what for destined - no matter. And the chip's output for grinder has 7kOhm to GND in both polarity, while the rest two outputs have 30kOhm or infinity dependly of polarisation. Looks like this one output destroyed. However if you advise about Microschalters will be good It makes me happy man... :-).

Hello,

So you suggest that in slow handy test the switches may seem as working ok but while normal dynamic operating are just working to slow? Hmm, I will try to check this.

In the meantime I noticed following strange behaviour o the control board. Normally on the output should be stable 5V, when activating the driver should appear 0V. At me there is in stable some HighImpedance state, and when should activate the grinder I get there 2.5V - just in momment when it should appear 0V. Maybe you are right about switches, but it is digital chip and should have 0 or 5V but almost for sure not 2.5V. Specialy that on other two outputs there is just as should be (0 or 5V). Because I don't have switches in my hands but have my head, I will add some driver trasistor (it is simple) and check this. Later will buy the switches to replace them. Could you pls provide me with partnumbers of these switchec, are both the same?

Hello!

Unfortunately here are some holidays for next 4 days so I can't buy new switches while I am dying without my coffee .

As I am almost fully sure that the problem is broken output of the processor and I did following:
- cut by half green wire coming to power supply board (5 counting from up). It is wire for controlling the grinder.
- soldered aditional small transistor to amplify and invert the signal from broken processor port.
Needed any bipolar transistor NPN with higher gain, I have used BC817-25. It's collector to the wire going to PS-board, emitter to brown wire of PS-board connector (the highest one, it is GND), base through serial resistor 22kOhm to the wire coming from controller board.

Machine has started work like new one. Grinder starts turning in momment when should do, an adjustment of coffee strongness works properly (time of grinding up to 10sec).
Coffe is OK .

So it seems that my diagnose of broken processor output was right. However I don't say that replacement of switches wouldn't solve the problem - but don't believe in this... Hope my solvation can help to anybody in the future when have no switches to try to check it.

Dear Black Sheep - thanks you for your kind answers. Vielen Dank und beste Grüße .

It is really possible that in my case was just broken processor. While in many other cases can be faulted one of the microswitches.
Finaly there can be few reasons giving the same result.

Regards!