Installation guide

Troubleshooting
Block Descriptions for Option 501, 502, 503, 504
1-117
Overall Block Description for Option 501, 502, 503, 504
Overview
The objective of this overall block description is to provide a functional overview of the
Agilent E4438C ESG vector signal generator with Option 501, 502, 503, 504. Some of the functional blocks
discussed are common to many types of instruments while others are more specific to signal generators.
• Common Functions:
— Power Supply
—CPU
— Input/Output Interface
• Specific Signal Generator Functions:
— Frequency Generation
— Output Power Level Control
—Modulation
A6 Power Supply
The main power supply converts line voltage (120 Vac or 240 Vac) to regulated dc voltages. Some of the
required dc voltages are not directly provided by the main power supply and are generated by converting the
main power supply voltages. Most of the conversions are performed on the A23 Motherboard, but a few are
performed on individual assemblies.
A24 Line Module
The line voltage is connected to the power supply through the A24 Line Module. Line voltage selection isn't
required because the A6 Power Supply automatically detects and adjusts to different line voltages. The power
supply has an internal line fuse, but if the fuse opens, the power supply must be replaced; it is not field
repairable.
A12 CPU
The A12 CPU controls all activities in the signal generator. It translates information entered from the front
panel keys, LAN, GPIB, or Auxiliary Interface (RS-232) into machine level instructions and communicates
these instructions on the internal buses. The A12 CPU also monitors critical circuits for unleveled and
unlocked conditions and reports these problems on the display.
Input/Output Interface
The Input/Output Interface is located on the front panel and includes the A1 Keyboard, the A2 Display, and
the On/Off power switch. The user interface consists of the front panel keypad and the display softkeys. The
current signal generator state is displayed on the A2 Display. Above the power switch, are amber and green
Light Emitting Diodes (LED). When the amber LED is lit, it indicates that line voltage is present and that the
signal generator is in standby mode. When the green LED is lit, it indicates that the signal generator is in the
power-on mode.