A common failure involves two specific resistors (R79 and R80) on a daughter board inside the amp. Repair enthusiasts often replace the original 3W resistors with 5W 5.6 Ohm resistors to better withstand the heat and prevent future burnouts.
But here was the weird part.
that hold a lethal charge even after the unit is unplugged. Always discharge the main filter capacitors (typically 400V rated) before touching the power board. Further Exploration Review the Logitech Support Page logitech z906 service manual hot