How to restore sound on a JVC LT-49C870(B) TV after disconnecting a surround sound system?

 
I have a JVC LT-49C870(B) TV that used to work with a surround sound system for six years. I recently removed the surround sound system and returned it to the owner. Since then, I have no sound output from the TV's in-built speakers. I have checked the manual and the settings, but I cannot find the problem. I only use a Chromecast device to stream content, and the image quality is fine. Is there a simple solution to this issue? I appreciate any help.
 
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