Non-invasive local probes are needed to characterize bulk defects in binary and ternary chalcogenides. These defects contribute to the non-ideal behavior of topological insulators. The bulk electronic properties are studied via Te-125 NMR in Bi2Te3, Sb2Te3, Bi0.5Sb1.5Te3, Bi2Te2Se, and Bi2Te2S. A distribution of defects gives rise to asymmetry in the powder lineshapes. The Knight shift, line shape, and spin-lattice relaxation are investigated in terms of how they affect carrier density, spin-orbit coupling, and phase separation in the bulk. The present study confirms that the ordered ternary compound Bi2Te2Se is the best topological insulator candidate material at the present time. These results, which are in good agreement with transport and angle-resolved photoemission spectroscopy studies, help establish the NMR probe as a valuable method to characterize the bulk properties of these materials.