Sympthoms:
It has stopped during the washing process and raised error 'Uc'. Unplug power cord and plug it back caused, that whole panel remained dark. After pressing "On/Off" button one could hear double click of internal relay. 'Uc' error signals problem with power supply and this is what we can find everywhere in the internet.
Diagnosis:
Of course, I measured voltage in the network and it was ok. I had a feeling, that problem was somewhere inside. I took out the top cover and checked point by point if power supply is there. When I reached main PCB, I was almost sure, that problem is there, but to exclude other factors I wanted to check other sensors, if they are not confusing this control unit. For that I needed wiring schematic, so I started searching internet. This is how I found Pico Electronic site where author described his problem with different model. What was meaningful, that in the text he mentioned about schematic from service manual. I was partially right assuming, that I will not find papers to my model, but it turned out that EcoBubble is long term project, and in each new model base is the same and only small improvents are introduced. That let me to define destination of all connectors on PCB and understand its relationships
Like in most of all modern devices, where there is not phisical switch, but small microstick a part of device need to be under constans power and after pressing this button, main power is turned on. The same is here. Main power is connected to main relay on the board. When it is turned on, it pass power to rest of device. It is controlled by heart of device - microcontroller.
If this error shows during voltage surge, it would be good to check if internal power supply levels are ok. Knowing typical design of switching power supplys it is easy to find its outputs. In this circuit it should be 5V, 12V possibly 15V. And those values I have found. So, the device has everything to proper work and there should be no short circuits. This is also confirmed by the fact, that after pressing button, there is double clikck of relay.
On the begining I decided to check this device using thermovision camera. Voltage regulators and microcontroller were about 30C. Suspected relay was much warmer with his 42C.
After that, I have checked if power is passed to second connection from the relay. As expected, it was not. So either relay is demaged or voltage of its coil is to low and it can't make a good quality connection. Checking voltage level between VCC and collector of switching transistor I realised that it has everything to proper work. The last remaining test was to make physical bypass. I turned the device on and when relay clicked, I made the connection using stiff wire. Whole washing mashine was alive again!
Fixing:
Replacing relay is trivial. Taking out PCB from plastic case, being under sylicon cover is not that trivial. Using knife and hammer method plus a bit of carefulness it is the only I can recommend.
Schematic:
This papers let me to understand how hose EcoBubbles works
samsung_wf10614yke-xeg_wf600b0bkwq-eo_wf602b2bkwq-eq_washing_machine.pdf