I have found what was wrong. So stupid and rare event. R31 and R39 were marked as 100Ohm resistors, but real resistance was 100KOhms. I managed to backtrack origin of these resistors and realize that they were bought in local store very cheaply. Now I know why they were so cheap. The measured voltage and calculated one didn't match, so I measured resistance of both resistors in the line (1.5Kohms and 100Ohms). Whole batch that I bought was with wrong markings.
Hi everyone. I am new to this forum, but not to electronics. I have assembled and successfully programmed 2 UniSolders 5.2 units. Unfortunately I am stuck at calibration. Both units that I have assembled show the same symptoms (see attached video). I have checked voltages on some crucial components. No current through 10 Ohm calibration resistor. U14 voltage OK. U12(pin 3) voltage 2.7V (OK), but Q22 gate 2.4V and Q22 source 2.71V. It seams that Q22 is OFF. Also there is one important thing about calibration that I didn't able to find on forum and that is whether touch sensor (SLEEP function) for handle should be connected to the unit or not during calibration. I could replace some components, but I am not so sure that it would solve this problem. If anyone have a clue what could be the problem, I would appreciate any information or hint.
