msthang332001, Make sure the Line In Switch is in the off position if not using the Auxiliary Input, make sure the line-in switch, located on the back of the system near the auxiliary cable, is in the off position. It may be a bad volume switch/connection, bad speakers/connection, possible fuse blown for internal amp. if equipped or could be a faulty amp. The guide 1st link below will help get you inside the device to check/test components. If under warranty have repaired/replaced/refund under the warranty. Last link is Crosley support page. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
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http://www.crosleyradio.com/support