This paper is a progress report on the studies of the BNL volume H−ion source. We have measured the H−yield,IH−, and the ratioIe/IH−as function of the size of the extraction aperture, strength of the conical filter field, size and position of the filament, and of the phase of the filament heating current. The H−current density in the extraction aperture was lower for the largest aperture, while there was a broad maximum when the conical field varied. Position of the filament and the phase of the filament heating current are very important parameters.