Hartmann + Lammle Electronic 781‑466‑599 is a hydraulic amplifier used to drive solenoid valves in industrial process control systems. Common failure modes for this class of units include power supply voltage drops, overheating of the output transistors or MOSFETs, and degradation of the internal driver IC due to over‑current or thermal cycling; insulation resistance between the high‑voltage input and chassis can also fail after long operation. First‑check diagnostics should verify that the unit receives its rated DC supply voltage within tolerance, inspect for visible signs of component burn or excessive heat on the board, and confirm that the output coil currents match the manufacturer’s specifications using a calibrated multimeter or oscilloscope.[oss-gpt-20b]