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RF Vector Network Analyzer
N9923AN
Front Panel Group
The front panel group consists of the following assemblies:
•
A3 Front Panel Interface Board
•
A2 LCD Assembly
Refer to
Figure 5-1
for a simplified overall block diagram which includes the front panel
group.
A3 Front Panel Interface Board
The main function of the A3 front panel interface board is to support the user interface but
it also contains the digital power supplies.
Microcontroller and CPLD
The Microcontroller and CPLD sense the keypad keys and the RPG (rotary pulse
generator) knob on the front panel. The Microcontroller communicates with the A5 system
board via a USB interface.
There is no separate ID EPROM on the A3 front panel interface board. All ID information
is stored in the Microcontoller.
Front Panel LED's and ON/OFF Button
The power for the Keypad LED's generated on the A3 front panel interface board is derived
from the +5 V digital supply. The Keypad LED's are turned on for a few seconds following
each key press. This function is controlled by the firmware on the A6 SOM board.
The On/Off LED is controlled by a signal from the A5 system board. The connections for
the On/Off Button and LED are direct to the A5 system board.
Real Time Clock Battery
The battery for the RTC (real time clock) on the A6 SOM board is located on the A3 front
panel interface board and is connected to the A6 SOM board via the A5 system board.
Backlight Power
Power for the backlight on the A2 LCD assembly is generated on the A3 front panel
interface board. Digital 5 volts is converted to approximately 25 volts. The actual voltage
determines the brightness of the backlight. Two control lines from the A5 system board
control on/off and intensity functions. These control lines are driven by the system monitor
microcontroller on the A5 system board.
Speaker and Headphones
The speaker is located on the A3 front panel interface board. Left and right audio signals
from the A6 SOM board go to the headphone jack on the A5 system board. These signals
are then combined (on the A5 system board) to create a single mono signal for the speaker.
An amplifier on the A3 front panel interface board drives the speaker. Plugging in the
headphones disables the speaker output.
Service Guide N9923-90005
Theory of Operation
Front Panel Group
5-5
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Troubleshooting
