A high power RF or microwave amplifier may amplify an RF or microwave input signal. The high power RF or microwave amplifier may include an input signal divider (DIV) that has an input port that receives the RF or microwave input signal and that divides this input signal into multiple sub-input signals; multiple power amplifier units (PAUs), each having an input port that receives an RF or microwave signal, an output port that delivers an amplified version of the received RF or microwave signal, and an interface port; an interface control unit (ICU) that communicates with each PAU through its interface port; and an output signal switching combiner unit (SCU) that coherently sums the outputs of the on-line PAUs and delivers this to an output port. The ICU may set one or more of the PAUs to amplify one of the multiple sub-input signals (hereinafter referred to as on-line PAU in on-line mode); monitor each on-line PAU to verify that it is operating within one or more pre-determined PAU specifications; and upon detecting that one of the on-line PAUs is no longer operating within the one or more pre-determined PAU specifications (malfunctioning PAU), set the malfunctioning PAU not to amplify one of the multiple sub-input signals and not to be available to be switched to the on-line mode by the ICU (hereinafter referred to as off-line PAU in off-line mode).