12-6 Service Guide
Theory of Operation 8719ET/20ET/22ET
Power Supply Theory 8719ES/20ES/22ES
RF Network Analyzers
Power Supply Theory
The power supply functional group consists of the A15 preregulator and the A8 post
regulator. These two assemblies comprise a switching power supply that provides
regulated dc voltages to power all assemblies in the analyzer. The A15 preregulator is
enclosed in a casting at the rear of the instrument behind the display. It is connected to the
A8 post regulator by a wire bus A15W1. Figure 12-2 is a simplified block diagram of the
power supply group.
Figure 12-2 Power Supply Functional Group, Simplified Block Diagram
A15 Preregulator
The A15 preregulator steps down and rectifies the line voltage. It provides a fully
regulated +5 V digital supply, and several preregulated voltages that go to the A8 post
regulator assembly for additional regulation.
The A15 preregulator assembly includes the line power module, a 60 kHz switching
preregulator, and overvoltage protection for the +5 V digital supply. It provides LEDs,
visible from the rear of the instrument, to indicate either normal or shutdown status.
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