An electrostatographic reproduction apparatus having a transfer assembly, including an electrically biased transfer roller in nip relation with a dielectric support member, for effecting transfer of a pigmented marking particle image from an image area of a dielectric support member to a receiver member in transfer relation with the dielectric support member in the transfer nip, a mechanism for cleaning the transfer roller including a control for the electrical bias on the transfer roller. The electrical bias control has a power supply generating an electrical output, of a settable polarity, connected to the transfer roller for applying an electrical bias of a set polarity thereto. A timing signal generator produces signals respectively corresponding to the location of a receiver member relative to the transfer nip. A mechanism, responsive to the signal from the timing signal generator, indicating the passing of the trail edge of a receiver member through the transfer nip, reverses the setting of the polarity of the electrical output from the power supply so as to prevent transfer of residual marking particles from the dielectric support member to the transfer roller.