Agilent Technologies N5242A, Service Manual

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Service Guide N5242-90001 5-31
PNA Series Microwave Network Analyzers Theory of Operation
N5242A Digital Processing and Digital Control Group Operation
Front Panel Subgroup
The front panel subgroup contains the following assemblies:
• A1 Front Panel Display Board
• A2 USB Board
• A3 Display Assembly
• Keypad Assembly
A1 Front Panel Display Board
The A1 front panel display board detects and decodes user inputs from the keypad
assembly and front panel knob, and transmits them to the A17 CPU board by way of the
A14 system motherboard. It also decodes video data from the video processor on the
A17 CPU board and supplies this to the A3 display assembly. Power from the power bus on
the A14 system motherboard is buffered and routed to the keypad assembly and the
A3 display assembly. All data and power signals are routed through a single cable
connector to the A14 system motherboard.
The A1 front panel interface board also includes a speaker that emits the audio signals
received from the A17 CPU board.
A2 USB Board
This board provides four universal serial bus (USB) jacks that are industry standard 4-pin
connectors allowing multiple USB devices to be connected to the analyzer’s front panel.
A3 Display Assembly
The A3 display assembly contains an 10-inch LCD with associated drive circuitry and
backlight inverter. Two cables between the A3 display assembly and the A1 front panel
display board provide all necessary power and data for normal operation. The two cables
are:
1. A cable to the inverter that supplies buffered power.
2. A cable to the display circuitry that supplies decoded data from the video processor on
the A17 CPU board and the necessary drive circuit power. The video data received from
the A17 CPU board includes the following:
Keypad Assembly
The keypad assembly provides user interface to the analyzer. The front panel rotary pulse
generator (RPG) knob is not electrically connected to the keypad, but rather provides user
inputs directly to the front panel processor.
• digital TTL horizontal sync • digital TTL red video • blanking
• digital TTL vertical sync • digital TTL green video • data clock
• digital TTL blue video