Hello, I have a problem with the Fronius 1500 transpocket welding machine. Maybe from the beginning, a potentiometer was supposed to be added to the welding machine to control the welding current on the cable, i.e. External control with switch for selecting the control potentiometer. This was to be done by a switch of the two-state ON-ON type, picture. After putting everything together, I waited for a new potentiometer identical to the one used in the welding machine, i.e. 25k. Unfortunately, I temporarily soldered a 10k potentiometer onto the external cable to check it and, unfortunately, I left it there. My father came and wanted to see how it worked and connected it. As long as he was welding on the welding machine`s control, everything was apparently OK. After switching the control to external, all the diodes lit up and since then the control has not worked. The welder produces an arc normally, but the current cannot be increased or decreased. The potentiometer is OK. (checked) the diode in the welding machine on the board (marked in Figure 2,3,4) reacts to turning the potentiometer and lights up brighter and darker as it is turned. 5v is supplied to the potentiometer. The voltages at the control points match, figure 5. At idle speed it is approximately 75V. What can I check and what could be damaged? Thanks for any suggestions. Edit: added 2 pictures with damaged resistors and a question on how to check the systems next to them. The chips are SG3644M
