Methods of regulating an output voltage of a switched mode power supply having a variable input voltage and a power switch include adjusting a reference voltage to adjust a duty cycle of a control signal for the power switch. A plurality of printed circuit boards are mounted end-to-end on the support structure. The header extends from the heater into the housing. It is a low cost, low viscosity, commercially available, non-hazardous, water soluble, low toxicity chemical that burns cleanly leaving little or no residue. , a target pressure in the negative pressure chamber. The dielectric layer is thicker than the chemox layer.