This paper is a progress report on the studies of the BNL volume H− ion source. We have measured the H− yield, I{sub H}−, and the ratio I{sub e}/I{sub H}− 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. 5 refs., 10 figs., 1 tab.