RVtrike

Advice please, 2009 Royal star venture. The audio control shows no sign of life. checked connections. Will clean and reconnect after reading threads here. Is there any other secret repair. I have also checked the fuse and voltage to the brown/white wire. If it doesn't come to life what are the alternatives. How do you tell if it's the brain box or the controller and display on the handlebar? Is there repair for them? Where? cost? or replacement? where? cost? Thanks for your help.