A2 Lcd Assembly - Keysight N9912A Service Manual

Theory of Operation
Front Panel Group
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.
Digital Power Supplies
Digital power supplies on the A3 front panel interface board are driven by the
Unreg DC voltage from the A5 system board.
The 5 volts produced is used on the A3 front panel interface board and the A5
system board.
The 3.5 volts produced is used on the A3 front panel interface board, the A5
system board, and the A6 SOM board.
Both supplies are either on or off together except for power supply sequencing
and are controlled by the System Monitor Microcontroller on the A5 system
board.

A2 LCD Assembly

The A2 LCD assembly contains a 6.5-inch, 640 x 480 TFT color LCD with
associated drive circuitry and backlight inverter.
The LCD backlight is created by LED's connected in parallel stacks. Backlight
brightness is a function of the backlight power that ranges from 22 to 27 volts.
Refer to "Backlight Power" on page 5-4 for more information.
The backlight LED's are arranged along the top and bottom edges of the
display. There are three stacks on each edge.
Keysight N9912A Service Guide 5-5