Agilent Technologies HP 8719D Service Manual page 334

Display Power
The A8 assembly supplies + 5VCPU and + 65 V (not used) to the A22 GSP
interface board. The +5VCPU is routed to the A19 GSP where it is regulated
to +3.3 V and sent to the display. The A19 GSP also controls and supplies
power to the A20 backlight inverter. The voltages generated by the inverter are
then routed to the display. Display power is not connected to the protective
shutdown circuitry so that the A18 display assemblies can operate during
troubleshooting when other supplies do not work.
Note
If blanking pulses from the A19 GSP are not present, then
Digital Control Theory
The digital control functional group consists of the following assemblies:
Al front panel
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These assemblies combine to provide digital control for the entire analyzer.
They provide math processing functions, as well as communications between the
analyzer and an external controller and/or peripherals. Figure 6-l is a block
diagram of the digital control functional group.
Theory of Operation 12-7