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Circuit Descriptions, List of Abbreviations, and IC Data Sheets
9.3.13 HOP Signal Processing
The Y/G, B/Pb, and R/Pr signals are fed to their respective
sharpness controls. If the input is a YUV signal, the Y signal is
fed to pin 28 of 7600. The U and V signals are fed to the Tint
Control circuit and then to Pins 27 and 26 of 7600. If the input
is RGB, the signals are fed to Pins 31, 32, and 30 of 7600 to an
RGB to YUV converter. When RGB input is used, there is no
Tint control available for the signal.
The input selector switch in 7600 selects between the YUV on
Pins 28, 27, and 26 or the output of the internal RGB/YUV
converter. The signal is fed to the RGB insertion circuits where
the OSD is inserted. The signal is then fed to a White Point
circuit and then to the Output Amplifier. The White Point and
Output Amplifier have the Drive controls and Cut-off controls.
Input from the ABL line on Pins 43 makes adjustments in the
brightness levels to adjust for changes in beam current. The
AKB pulses from the CRTs are fed to pin 44 to the Cathode
Calibration circuit. The Cathode Calibration circuit adjusts the
Cut-off levels of the CRTs to maintain the correct grey scale
tracking. 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 AKB line to set the Black level and
the maximum drive voltage for the cathode. Once the
Calibration has taken place, the Output Amplifiers 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
picture. 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 7600 is controlled by the microprocessor via the I2C buss on
Pins 10 and 11. Geometry and Drive settings are stored in the
Memory IC located on the HOP panel.
Figure 9-20 HOP signal processing
9.3.14 HOP Sharpness Control
DPTV565 AA
Figure 9-21 HOP sharpness control
The Sharpness controls for the YUV/RGB signals are located
on the HOP panel. Since all three circuits are basically the
same, only the Blue one will be discussed.
The Blue signal is fed to pin 1 of 7410. It is also fed to a Low
Pass filter consisting of 5411 and 5410. This path is amplified
by transistor 7411. The Low Pass filter blocks the higher
frequencies as well as shifting the phase of the signal. The
output of the Low Pass filter is also fed to pin 4 of 7410. The
mixing of these two-phase shifted signals only allows the High
frequency component to be amplified and output on pin 12. The
gain of the High frequency component is controlled by the
Sharpness voltage, which is applied to Pins 8 and 10. The two
signals are combined at pin 12 of the IC. If the input was a Blue
9.
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