i bought a danby designer microwave at a garage sale. It appeared to be new. It worked fine for a week, but now the control panel is dark and it will not heat food. The internal light comes on, but that is all. I have unplugged and replugged it, pressed the reset button and a variety of other buttons, but nothing happens. From time to time it does beep as though it is waiting for me to take something out. Any ideas, or is this just hopeless?