The control pod's LCD backlight and the power button are frequent fail points. Overheating of the LM217 voltage regulator is also common, often caused by faulty resistors on its ADJ pin.
Logitech Z-5500 Power Supply to Control Unit Repair help wanted logitech z-5500 schematic diagram
, though these focus more on wiring than internal component schematics. Common Repair & Technical Details The control pod's LCD backlight and the power