My Dewalt dc911 charger works but no sound?

Either the output stage of the radio amplifier are faulty or the speaker(s) are open circuited. Unfortunately there is no easy fix without a dismantling of the unit and testing. Sorry

You burned out the AC circuit. Congratz, at least your radio still works. Use it on battery or take it to a radio technician to diagnose if it can be repaired. Presume it's worth.

DEWALT DC012 Worksite Charger Radio

This is what dewalt is saying...The Dewalt 12V/20V MAX work-site charger/radio functions as an AM/FM radio and recharges your 12V/20V Dewalt batteries (batteries not included). The 3-stage charger can recharge your batteries in as little as 1 hour, and the radio can run off 12V/20V batteries for cordless operation

• 2 AC power outlets offer more versatility for jobsite power
• Auxillary & USB ports allows for connection to CD, MP3, portable satellite receivers, and other digital audio devices.
• USB port allows device to be charged via USB when radio is plugged into a wall outlet
• Class D amplifier, woofers and tweeters provide full range of high and low sound for optimum sound quality,( hope this helps)

i have put 2 new batteries but cant get radio 2 work

More than likely your internal charger is faulty. Inside your inernal charger unit check the 2 anmp fuse which is white in colour.

Replace the AA batteries they are located inside the battery chager. these batts. control the radio and memory stations.

could be a fuse in the radio. check with your local dewalt dealer.

http://www.dewaltservicenet.com/Products/DocumentView.aspx?productid=6159&typeId=6613&documentId=21603

Inside my (older, non nano) dewalt charger there is indeed a fuse, which has never blown (yet).
I'd be suggesting that you contact dewalt before you void your warranty by opening it up though.

Decase by removing the eight screws on the back. Check the charging fuse isnt blown. You will find it on the underside of the square circuit board that mounts on the back of the charger port.