There are multiple ground wires in the 40 pin ribbon cable (that becomes a round cable between the controller card and the RL02). The RL02 end (at logic board J12) has ground on: VV, UU, LL, KK, FF, EE, BB, AA, U, V, P, R, K, L and A. Having all those fail would be pretty unlikely... It wouldn't hurt, though, to have frame ground (the cabinets) all tied together and make sure they are properly grounded to the power outlet ground pin. -Charles