The Z-5500 uses a Switching Mode Power Supply (SMPS).
This is the most common deadly failure. On the schematic, look for a small TO-92 transistor labeled Q101 near the standby power transformer. It controls the main relay. When this transistor fails short, the main amp never turns on, or the pod stays dark. logitech z-5500 schematic diagram
The Z-5500 is split into two primary electronic sections: the (the "pod") and the Main Power Amplifier Board located inside the subwoofer. 1. The Control Pod (Pre-Amp and Logic) control pod Go to product viewer dialog for this item. The Z-5500 uses a Switching Mode Power Supply (SMPS)