The effect of MnO additions on the formation of the (Bi,Pb)2Sr2Ca2Cu3O10-y phase has been studied in view of the mechanical reinforcement of the Ag sheath of (Bi,Pb)2Sr2Ca2Cu3O10-y superconducting tapes by alloying and/or dispersion hardening. DTA measurements showed that the onset temperature of partial melting occurring in the precursor powders is slightly lowered when MnO is added. From lattice parameter calculations as well as EDX measurements it follows that Mn substitution in the (Bi,Pb)2Sr2Ca2Cu3O10-y phase, if any, is limited to below 0.1 at.%. The results are compared to those obtained in a previous work on TiO2 added to (Bi,Pb)2Sr2Ca2Cu3O10-y.