Fluke 9640A Series, Instruction Manual

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Theory of Operation
Introduction
6
6-3
Introduction
This chapter of the manual provides the theory of operation for the Instrument. The
theory is presented at a high-level and is supported by an overall functional block
diagram. Since the Instrument is supported at the module (board) level, the theory is often
a useful troubleshooting tool for isolating faulty PCAs. The Assembly numbers
(modules/PCAs) in the theory correspond to the replaceable assemblies described in
Chapter 8, List of Replaceable Parts.
Overall Functional Description
Refer to the functional block diagram shown in Figure 6-1 while reading this description.
In addition to identifying all of the assemblies contained in the Instrument, this diagram
provides a functional view of the data flow between the assemblies. When appropriate,
simplified schematics also accompany the description. These simplified schematics,
Figures 6-2, 6-3, and 6-4 are located at the back of this chapter. Assembly
interconnections and cable identification is detailed in Chapter 7, Maintenance.
The following list identifies the eight major assemblies that comprise the Instrument and
includes a description of the basic functions each assembly performs:
A1 Synthesizer PCA Develop frequency for output, and voltages for isolated
(floating) functions
A2 RF Output PCA Divide, filter, amplify, control, and attenuate RF Output
A3 Digital PCA Optical isolation and routing of digital control data (IEEE-488
(GPIB) and serial data)
A4 Power Supply PCA Ground referenced power supplies and driver for Low
Voltage Transformer (T2)
A5 Interconnection PCA Rear-panel accessible connectors and switches for remote
communication.
A6 Front Panel Assembly Front panel user interface (UI) for local operation, includes
the A6A1 Display PCA and the A6A2 Keypad PCA
A7 Power Transformer
Assembly
Also provides the
±
48 V ac (A7T1) for driving the A4 Power
Supply PCA
__ Rear Panel Provides the mounting location for ports, connectors, and
switches needed to externally access and influence the
operation of the Instrument.
A9 Leveling Head Leveling, control, and attenuation of the RF Output Signal