Speaker powers off randomly. Solution (from manual page 19): Auto-off is enabled by default. To disable: Press Power + Volume Down for 5 seconds until you hear "Auto-off disabled."
While this guide covers daily operation, you may need the technical circuit diagrams for repairs. You can typically find the official PDF download on the JBL Professional website under the "Archived Products" or "Karaoke Systems" section. jbl rma 220 user manual NEW%21