Plug in the control console and the power cable. Turn the unit on to check if the console lights up normally and accepts inputs. Test audio at a very low volume using a temporary source.
If you want to dive deeper into repairing your specific sound system, tell me: What is your Z906 displaying right now? logitech z906 service manual fixed verified
Test the main switching transistors bolted to the aluminum heatsink. If your DMM reads zero ohms across the Drain and Source pins, the MOSFETs are shorted and must be replaced. Symptom 2: The "Three Lights of Death" / Console Freezing Plug in the control console and the power cable
For those with soldering skills, a multimeter, and patience, many Z906 units can be repaired by replacing specific failed components. If you want to dive deeper into repairing
Ensure the control console cable is securely bolted to the DB-15 port on the back of the subwoofer. A loose control pod connection mimics a dead power supply. Step 2: Test the Main Fuse