Hello and thank you for your question, I look forward to assisting you today. Unplug the power then press and hold the power button down for about one minute and let me know what happens.
What type of speaker extension was this?
Plugged into the audio out port I presume?
How about on the Yamaha end. What was the cable plugged into there?
Was there a possibility you had plugged the cable into the output of the Yamaha instead of the input?