No sound in karaoke machine

Question

I have an optimus Karaoke machine cat. # 32-1163, it had belonged to a friend and he said it made a popping sound when he plugged up the aux. mode and now there is no sound from the internal speakers. all components are working with the exception of sound. Does this machine need the remote to work properly? all volume controls and settins are also on the face of the machine. Can I possibly get my hands on a schematic and repair manual for the piece of equipment?