Im currently repairing an old boat anchor Rotek 3960. I replaced a couple bad parts, but two components were charred beyond recognition. The service manual is incomplete or detail got lost in the scanning process.
I would guess tantalums, but im not sure. The current output is not only dc, but also ac in the range of 1khz. So adding a bypass capacitor might not be beneficial in the current sense assembly.
Thankful for suggestions!
I think I should clarify what I replaced in the affected circuit. The zener VR5 was burned. Both VR5 and VR6 are 10V zener diodes. In the current configuration they protect the current output from overvoltage plus or minus 10.5 volt to GND. In the scan one can barely recognize a connection to the output of the power amp (the common input on the CMOS switches IC4, IC5, IC6 at the top).
I suspect a capacitor involved somewhere to reduce the CMOS and relay switch noise maybe. There could also be another protection from the output of the amp to GND, to protect the switches and resistors. I attached a functional diagram!
Well, it was just two more protection diodes mirrored on the other side. They don't seem to show up in the service manual.
Thanks to velik_kazakov for helping me with the service manual and raking some photos of his device
