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HOP IO (Figure 29)
IC 7800 develops the analog control voltage for the HOP circuit. The I2C bus from the GDE micro-
processor controls the IC. This IC is located on the SSM.
FIGURE 29 - HOP I/O
CRT panel (Figure 30)
The Red, Green, and Blue signals from the HOP panel are fed to their respective CRT panel. The
signal is fed to the emitter of 7200 and then to 7202. The output of 7202 is fed to Pin 2 of 7201
which drives the cathode of the CRT. AKB drive is output on Pin 7 and fed to the HOP panel.
The CRT circuit is powered by the +200-volt supply from the LSB. If there is a problem in this cir-
cuit, the one resistor, 3217, will open. If this resistor opens, the CRT will have excessive drive caus-
ing it to go to maximum brightness. This will cause an over current shutdown on the LSB. In nor-
mal operation, the G1 voltage will measure approximately minus 20 volts. During blanking, this volt-
age will go to a minus 200 volts. The Filament voltage will measure approximately 6 volts DC. If
drive is removed to any of the CRT boards, the CRT will be driving into saturation, causing an over
current shutdown.
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