An MHD generator includes external electrical connectors between adjacent discrete electrodes in one wall of the generator duct, which has opposed electrodes which may lie in a plane at an angle to the direction of gas flow. The electrical connection includes a circuit which adjusts the voltage between the connected adjacent electrodes to insure that the Hall voltage differential between the discrete electrodes which are adjacent to each other in the same wall of the duct does not exceed the damaging breakdown voltage. Indicator means when coupled to the circuits in accordance with the invention comprise diagnostic means which provide a graphic representation of voltage distribution along the length of the generator duct.