Philips Colour Television Service Manual page 91

Circuit Descriptions, List of Abbreviations, and IC Data Sheets
9.3.17 HOP RGB Amplifiers
Figure 9-24 HOP RGB amplifiers
The output of 7600 is fed to the RGB amplifiers before being
fed to the CRTs. Transistors 7720 and 7721 buffer the Blue
output on pin 42. The B-BIAS control voltage controls the gain
of this circuit. Transistor 7730 provides an additional voltage
gain for the signal.
Items 7710 and 7711 buffer the Green output from pin 41 of
7600. The G-BIAS controls the gain of the circuit.
The Red output from pin 40 of 7600 is buffered by 7700 and
7701. The R-BIAS controls the gain of the circuit.
The drive of the Red and Green outputs is compared with the
Blue drive by 7900-A. The difference signal is fed back to 7600
via the ABL line. If the Blue CRT is driven harder than the
Green and Red CRTs, the inverting input on pin 2 will become
greater than the non-inverting input on pin 3, resulting in the
output on pin 1 to go Low. The ABL line will go Low, causing
7600 to reduce the drive to all of the CRTs. This circuit prevents
the Blue tube from being over-driven.
9.3.18 HOP Analogue Control
Figure 9-25 IC7800 HOP analogue control
IC 7800 develops the analogue control voltage for the HOP
panel. The I2C bus controls the IC. This IC is located on the
HOP panel.
9.3.19 CRT Panel
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9.3.20 HOP Sync Switching and Processing
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DPTV585 AA
Figure 9-26 RGB amplifiers on CRT panel
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 on each panel. 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.
Figure 9-27 HOP sync processing
Horizontal and Vertical Sync from the SSB is fed to the HOP
panel via the SSM panel, when NTSC is used as the signal
source. In sets with the D Shell RGB input, 7110 switches
between the Vertical and Horizontal Sync on the cinch
connectors or the Sync from Pins 13 and 14 of the D Shell
connector. IC 7210 selects between the output of 7110 and the
Sync from the SSB. For separate Horizontal and Vertical Sync,
the output of 7210 is fed to the multiplexer IC 7330, which is
used as a switch. In the case of Sync on Y or Sync on Green,
pin 19 of 7210 is fed to pin 18 of 7210 to a Sync Separator. If
separate Horizontal Sync is present, the internal detector in
7210 turns the Sync Separator "off". The Sync output on pin 17
is fed to a Low Pass Filter, which separates the Vertical Sync.
The Timer IC 7328 detects the Horizontal Sync and feeds it to
7330. The detected Horizontal Sync from 7328 is fed to pin 1 of
7330 to switch the IC to the pin 6 and 3 inputs.
9. EN 91
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