Power Supply Section; Power Supply Section Block Diagram - Agilent Technologies 4339B Service Manual

not lose its data when power is turned o . The EEPROM is mounted in a socket for easy
replacement.
Jumpers and switches set the 4339B conditions. Refer to Appendix B for more information.

Power Supply Section

Figure 4-7 shows the 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, voltage selection switch, and the varistors. The voltage selection switch selects the
ac line voltage either 230 V or 115 V. 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 the fuse F1, if the 4339B is turned on with wrong
line voltage setting selection, for example, 115V selection when using 230 V line voltage.
Note Because very high dc isolation is required between A3 Ammeter assembly
and the other assemblies, the 4339B has two independent dc voltage supply
systems.
Both of the transformer secondary voltages are approximately 14 V. One of the ac voltages 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 +5 V, +
12 V, and 12 Vdc. The dc voltages are supplied to all the assemblies except A3, either
directly or indirectly via the A1 assembly. The other ac voltage is recti ed and ltered on the
A3 Assembly. A dc-dc converter on the A3 assembly provides regulated +5 V, +12 V, and
12 Vdc for the A3 assembly operation.
Figure 4-7. Power Supply Section Block Diagram
T roubleshooting 4-9