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TV Signal Processor (Figure 5)
Red, Green, and Blue from the Trident IC is input on Pins 30, 31, and 32 of 7221, TV Display
Processor. The RGB/YUV matrix changes the signal to a YUV signal before feeding it to a
Color level control circuit. The signal is fed to the RGB insertion circuits where the OSD is
inserted. The signal is then fed to a White Point and Brightness Control circuit and then to
the CRT panel. The White Point and Output Amplifier have the Drive controls and Cutoff con-
trols. Input from the ABL line on Pin 43 makes adjustments in the brightness levels to adjust
for changes in beam current. The Cutoff
pulses from the CRTs are fed to Pin 44 to the Cathode Calibration circuit. The Cathode
Calibration circuit adjusts the cutoff levels of the CRT to maintain the correct gray scale track-
ing. When the set is first turned On, a calibration pulse is output on the RGB lines. The
Cathode Calibration circuit monitors this pulse on the Cutoff line to set the Black level and the
maximum drive voltage for the cathode. Once the Calibration has taken place, the Output
Amplifier switches to the RGB drive signal as the output. Horizontal and Vertical Sync is fed
to 7600 on Pins 23 and 24. IC 7600 processes the sync to provide the geometry for the pic-
ture. Horizontal drive is output to the sweep circuit on Pin 8. Vertical drive is output on Pins 1
and 2. East West drive is output on Pin 3. Sandcastle (SCO) is output on Pin 9. Horizontal
Feedback (HFB) from the sweep circuit is fed into the Phase Loop to phase correct the
Horizontal drive. IC 7221 is controlled by the Hercules Processor on the Family Board via the
I2C buss on Pins 10 and 11. Transistors 7226 and 7227 levels shifts the I2C buss level
between 5 and 3.3 volts. Geometry and Drive settings are stored in the Memory IC located
on the Family Board.
Deflection (Figure 6)
Horizontal drive from 7221 is fed to Transistor 7404 located on the Family board. This drive
circuit has two power sources. During startup, it is powered by the +6 volt supply. Once the
High Voltage circuit is running, it is powered by Pin 9 of the IFT. 7404 drives Transformer
5402 which drives the HOT (Horizontal Output Transistor). The HOT drives the IFT and the
Horizontal Deflection Coil. The IFT is powered by the VBAT (141 volt) supply.
The IFT produces High voltage, Focus voltage and G2 voltage to drive the CRT. In addition,
a 200 volt supply is produced to drive the CRT panel, a +14 and -14 volt supply for the
Vertical output, Filament voltage, +200 volt VideoSupply, and a +12V_lot supply.
Transistor 7408 monitors the IFT secondary to sense the presence of over voltage. If the
High Voltage goes High, the voltage on Pin 6 of the IFT will go High. When the voltage on
diode 6480 exceeds 15 volts, transistor 7408 will turn On. If 7408 turns On, it will turn 7407
On causing the x_ray protect line to go Low. The Processor will then shut the set down. In
addition the EW_DRIVE circuit is monitored. If the EW_DRIVE fails, transistor 7406 will turn
On constantly placing a dc voltage on the source. This will turn 7407 On.
IC 7451 is the Vertical Output IC. It is powered by the +14 and -14 volt supply from the IFT.
The Vertical pulse is rectified by 6458, keeping the V_PROTN line High. If the vertical output
should fail, the V_PROTN line will go Low. The Hercules processor will then shut the set
down.
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