Agilent Technologies HP 8719D Service Manual page 331

Power Supply Theory
The power supply functional group consists of the Al5 preregulator and the
that provides regulated DC voltages to power all assemblies in the analyzer. The
the display. It is connected to the A8 post regulator by a wire bus A15Wl.
Figure 12-2 is a simplified block diagram of the power supply group.
Figure 12-2. Power Supply Functional Group, Simplified Block Diagram
The Al5 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 Al5 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.
124 Theory of Operation