An adapter plate configured to be attachable to a universal platen of a cleaning unit for cleaning upper electrodes from a plasma processing chamber is disclosed, the adapter plate includes a support surface and a mounting surface configured to be fastened to the universal platen of the cleaning unit. The support surface is configured to support an inner electrode or an outer electrode of a showerhead electrode assembly for cleaning upper or lower surfaces thereof. The support surface having a first set of holes configured to receive pins engaged in an upper surface of the inner electrode, a second set of holes configured to receive pins surrounding an outer periphery of the inner electrode, a third set of holes configured to receive pins engaged in an upper surface of the outer electrode, and a fourth set of holes configured to receive pins surrounding an outer periphery of the outer electrode.