HP HP 8753E, Service Manual, Page: 454 / 612

A19 GSP
The A19 graphics system processor is the main interface between the A9 CPU
and the Al8 display. The CPU converts the formatted data to GSP
commands and writes it to the GSP. The GSP processes the data to obtain the
necessary video signals, which are then used for the following purposes:
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The video signals are used to produce VGA compatible RGB output signals,
which are routed to the Al6 rear panel.
The video signals are converted by an LVDS (low voltage differential signaling)
driver which translates the signals to low level differential signals to help
radiated emissions The converted video signals are then routed to
the A2 assembly, where they are received and sent to the Al8 display.
The A19 assembly receives the VCPU which is used for processing and
supplying power to the A27 backlight inverter (+ 5 and the Al8 display
(3.3
A27 Inverter
The backlight inverter assembly supplies the ac voltage for the backlight
tube in the Al8 display assembly. This assembly takes the + 5 VCPU and
converts it to approximately 380 with 5 ma of current at 40 There are
two control lines:
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Digital ON/OFF
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Analog Brightness
100% intensity is 0 V
50%
intensity is 4.5 V
Al6 Bear Panel
The Al6 rear panel includes the following interfaces:
TEST
SET
INTERCONNECT. This provides control signals and power to
operate duplexer test adapters
EXT
This allows for a frequency reference signal input that can phase
lock the analyzer to an external frequency standard for increased frequency
accuracy.
The analyzer automatically enables the external frequency reference feature
when a signal is connected to this input. When the signal is removed, the
analyzer automatically switches back to its internal frequency reference.
12-12 Operation