Help with my detector

I have a Garret Scorpion gold stinger that I bought last year and have a few issues with it. First of all the volume control doesn't seem to have any effect on the intensity of the sound, and also I can't get it adjusted to sound off on my poker chip with a small piece of gold. I've found a lot of tin cans, bottel tops a few square nails, a few coins and other stuff, but nothing of any value. Last year when we were up by Downieville Ca. in a campground we met another couple and they had a Fisher gold bug. His Fisher sounded off on the poker chip, but mine would not. I bought my Garrett from Kellyco so I decided to ask them if they do trade ups, but they don't so I ask them if they could check the detector out and see if it was funtioning properly no again. I found out that if you are a beginner and you buy a detector you won't know if it works properly or not due to the learning curve involved. If you know detecting like a pro you would know right off the bat. I've decided to see if I could find a school or a professional that I learn from in my area. We are members of really great club, but it is headquartered in Reno and haven't been associated with too many other members, but the claims they have does have gold. We generally find color in our pans, but it's just flakes and fines with an occational small picker. We have a sluce box, a desert fox, a rokon motorcycle and a lot of small prospecting equipment. Any help that anyone could give would really be apprecieted.