Power Supply Section; Power Supply Section Block Diagram - Agilent Technologies 4349B Service Manual

Power Supply Section

Figure 4-6 shows the Power Supply Section block diagram.
Figure 4-6. Power Supply Section Block Diagram
The ac line power is connected to the A5 AC Inlet Board Assembly, which consists of a fuse,
line switch, and varistors. The voltage selection switch selects the ac line voltage from 230V or
115V. According to the selection, the ac line power is connected to the corresponding primary
tap of the transformer. Varistor VR1 protects the circuit from surge voltage on the line power.
VR2 blows fuse F1 if the 4349B is turned on with the wrong line voltage setting selection, for
example, 115V selection when using a 230V line.
The transformer secondary voltage is approximately 14 V. This ac voltage is recti ed and
ltered by circuitry on the A1 Main Board Assembly, and produces approximately 14 Vdc. The
dc voltage is applied to the DC-DC Converter to produce regulated +5V, +12V, and 12 Vdc.
The dc voltages are supplied to all the assemblies, either directly or indirectly via the A1
assembly.
4-8 T roubleshooting