Dryer will run about 5 times before tripping the re-settable t-stat. I have cleaned the entire dryer lint system including the round lint trap ring on the left side of the drum, all the areas around the element, the hose behind the dryer and the vent from the inside to the outside. I have replaced both elements and the re settable t-stat. What else am I missing? Is there a circuit board that is involved in this system? Thanks for your help.