Agilent N5161A/62A/81A/82A/83A MXG Signal Generators Service Guide
Troubleshooting
Overall Block Description
1-3
Overall Block Description
The objective of the overall block diagram is to provide a functional overview of the Agilent N5161A/62A//81A/82A/83A MXG Signal
Generator. The major assemblies shown in the block diagram are described in this section. Familiarize yourself with this information before
you start troubleshooting.
The overall block diagrams for the N5161A/81A and N5162A/82A are identical, except for the A2 Vector Module. The A2 Vector Module
controls digital arbitrary circuitry operations in the N5162A/82A.
The N5183A includes an A7 Micro Deck and uses a different A3 RF assembly than that used in the N5161A/62A/81A/82A.
The following components are not shown in the overall block diagram, but are described in this section.
• A1 power Supply
• A5 CPU
• A6 DC-AC Inverter Interface Board
• A8 Floating BNC Bypass (N5183A)
• A9 Interface Board (N5161A/62A)
• Front Panel
A1 Power Supply
The main power supply is a switching supply designed with an automatic line-voltage and frequency selection. It converts line voltage (120
Vac or 240 Vac) to regulated dc voltages. The internal power line fuse is not replaceable. If the fuse opens, the power supply must be
replaced. All A1 Power Supply outputs, except for the 5.1V standby supply, are over current protected and will not be damaged if a
continuous short circuit occurs.
A2 Vector Module (N5162A/82A Only)
The A2 Vector Module, a self contained, fully enclosed, Baseband Generator assembly, supports digital modulation in the N5162A/82A. It
receives a 500 MHz clock signal and the main RF signals from the A3 RF assembly when digital modulation is turned on. The RF signals are
I/Q modulated, band-pass filtered, amplified, and returned to the amplification output stages of the A3 RF assembly.
A3 RF Assembly (N5161A/62A/81A/82A Only)
NOTE The N5161A/62A/81A/82A A3 RF assembly is not interchangeable with the N5183A A3 RF assembly.
The A3 RF assembly combines circuitry traditionally found on individual, interconnected assemblies such as the reference, synthesizer, and
output assemblies.
Reference Circuitry
The reference circuitry uses a 10 MHz VCTCXO oscillator. The circuitry is designed to lock to an external reference frequency between
1 MHz and 50 MHz, with a resolution less than 0.1 Hz. Without the flexible reference option (Option 1ER) the reference will only lock to an
external reference of 10 MHz.
The reference output signals are multiplied to provide the following signals:
• A 50 MHz reference signal to the synthesizer Frac-N and FM circuitry.
• A 500 MHz clock signal to the A2 Vector Module.
• A 1 GHz LO signal to the heterodyne (HET) band mixer.
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