Motorola MPPS-II 60/90 Power Pack w/lid

The cover of the amplifier houses the model MPPS-II 60/90 power pack. It provides a regulated 24 Vdc output at 1.8 amps maximum over an ac input voltage range from 38 Vac to 90 Vac rms. The input voltage waveshape is either a squarewave or a sinewave. The surge protector and the EMI filter protect the power pack and amplifier from transient spikes. An integral fast-acting zener diode provides additional surge protection. 

The preregulator is a fixed frequency switching regulator that presents a near perfect power factor to the input line and provides overvoltage and overcurrent protection. A precision output regulator provides a precise output voltage and is also protected against overcurrent and short circuits. If a short circuit is detected, the power supply shuts down and the regulator initiates a sequence of line test pulses at approximately one-half second intervals. The regulator continues these pulses for the duration of the short circuit but returns to normal operation when the fault is cleared.