SX PX73M Speakers Stopped Working

I have a SX PX73M that the piano speakers have stopped working. I can still get keyboard sounds through the headphones. My electronics guy was able to get keyboard sounds by bypassing the piano speakers to external speakers. He feels that the problem is some type of short to or in the internal speakers. He is hesitant to dig further into the machine and maybe cause further damage. I am looking for any advice on getting the internal speakers working again. Thank you for your attention and I look forward to any replies.