New Haven chime silent mantle clock

My clock works very well except it doesn't strike the gong on the hour it does chime first but will not gong,I believe that the person I bought it from has overwonde the spring and it won't sound.

Can anyone help me with this beauty,she works great on all of her other functions.I haven't got a pic but she is a standard three spring unit with chime silent in face of unit,the lack of the gong on the hour is it's only problem.

Thank you