I don_ know why but even if I dialed the good temperature (67C), it pass over and went to almost to 84C before I stopped it.Maybe it_ because the cover was put on, but it_ the way to go as written in the manual. Maybe the thermostat is defective Can_ say for now.But what I can said is, when I was sure the temperature was ok (please use a good thermometer to be sure), the process was perfectly timed and wow! The PCB was amazingly clean.I_ impress by the quality of this ultrasonic bath. Just be aware of the temperature mess.