The power level won't power down to 50% (to melt) but stays at 100%

So when you press the Power Level button does the display not change? Typically what you want to do is select the amount of time you want to cook, then press the Power Level button until it display 7 or 6 or 5 or whatever you want, then press Start. With older microwaves you often would hear the microwave generator power off and on throughout the cycle, with newer ones they seem to just run at a lower intensity without any noticeable change in pitch or speed.