Step-by-step diagnostic paths based on symptoms.
Measure the voltage outputs coming from the power supply board to the amplifier board. You should typically see a high-voltage rail (around 30V to 40V DC) for the audio amplifiers and a lower 3.3V or 5V rail for the logic board. The "Three Lights of Death" / Blinking LEDs
Perform a : Hold down the Input button on the control console for 5–10 seconds while the system is in standby.
If the reset fails, a hardware protection circuit has been triggered. Unplug all satellite speakers. If the error persists, the fault is internal to the subwoofer board.