Abstract: A dynamic calibration and self-check circuit for a mobile X-ray machine. A high voltage regulator circuit provides dynamic regulation of peak anode voltage and a tube current regulator circuit provides dynamic regulation of the X-ray filament current which controls the X-ray tube current. In the regulation of the anode voltage, a voltage sensor provides continuous feedback of the actual anode voltage of the tube to the regulation circuit. A processor selects a predetermined value for the pulse width duration of the high voltage regulator. When an exposure cycle commences, the preselective value is compared with the actual sensed value in an error amplifier. The error amplifier generates an error signal which varies the pulse width of the drive signal to control the peak high voltage to the anode. In the control of the tube current, a sensor which measures the actual tube current is compared with a predetermined value selected by the processor in a second error amplifier.