A light monitoring circuit for a manual to automatic record player conversion includes a reflected light sensor and an ambient light sensor. The reflected light sensor is used to determine whether a tonearm-raising piston is positioned under a blade secured to the tonearm. The ambient light sensor is used to detect the amount of ambient light. The signals from the ambient light sensor and reflected light sensor are provided to a circuit that modifies the signal from the reflected fight sensor based on the signal from the ambient light sensor, thereby reducing any likelihood of error due to variations in ambient light.