I purchased a 505 about a month and a half ago. Everything has been doing good till about a week ago. I was hunting and I was covering a lot of ground and I hadn't had any beep in a really long time. Usually on the beach I'm hitting something every foot. So I start to watch my screen which I try not to do to listen for tone instead of number. Well I come across a signal and get a number but no sound. So I turn the adapter that my headphones are in and the sound comes back. I'm not sure it's the adapter headphones or my machine. If I don't use headphones it's fine. Any ideas what one you think it is?