I believe in order to return for an exchange from Circuit City within their 30 day period, you have to have the box and copy of your purchase receipt. You should probably read through your information that they provided to you on returns and warranty service. It is not normal for the tube to be rattling - sounds like something is loose. I think your best bet would be to return to Circuit City and they may be able to check it out for you, or will give you an exchange if you have followed their procedures. If they cannot service the unit for you, you can contact our Customer Service department at (800) 843-8823 and we can issue you a return authorization number to return the unit to us for repair. Please make sure you get the serial number off of the unit before calling in. Because you have only had the unit for 2 weeks, it will be covered under our manufacturers warranty. We may need a copy of your purchase receipt also depending on the date of the serial number. If you have any other questions, just let us know.