Thank you for answering Coulomb. I make some tests, and what I can tell, 73.93 firmware after update I trying Your updated firmwares 273.63 and 273.78, and my serial number of inverter become 533533.... into a simple set of numbers. And I make conclusion my EEPROM also updated with 73.93 firmware. After that, I test x73.76, and after one morning I can tell, that is works better than before. My serial number is also original right now. I will be wait from you new firmware. Thank you for that, you save a lot of money for me. I will buy you coffee later. 😉 And one question in archive x73.76 there is 1,2, and 9, what is the difference between them? Thank you once again and have a nice day.