When I turn the knob to set the dryer to the drying cycle I have to hold the knob while I push the start button, it will start, but just as soon as I release the knob on the left side of the panel the dryer will stop. I can slid a piece of cardboard between the knob and the panel and it will work, but the knob will not turn. I can pull part way out on the knob and turn it. It will click at each cycle. I know my grandson turned the knob backward when he used it, did this break the knob or the timer? Do I need a timer to correct this problem or just a knob. Please reply. Thanks Lillian Roland