Philips 7592, Руководство по обслуживанию

Страница: 70 / 323

NON PIP Video Signal Flow
Figure 8
The first version to be discussed is the Non PIP chassis video path. The Main Tuner, AV1, AV2, and
Component Inputs are located on the Large Signal panel. The AV3 input is located on the Side Jack Panel. All
of these inputs are fed to the Small Signal Board, SSB, which plugs into the Large Signal panel. The Tuner IF is
fed to the SAW filter, 1451, and then to the Signal Processor, 7301, on Pins 1 and 2.Composite Video is output
on Pin 16 and is buffered by 7305 and 7331. Baseband Audio is output on Pin 27 and is buffered by 7307. This
signal is fed to the Sound Decoder IC for processing. The Video Signal is then fed to 7301 on Pin 24, which
selects between the composite signal and the MAIN-CVBS-EXT-IN. The MAIN-CVBS-EXT-IN is selected
composite Video or Luminance from AV1, AV2, or AV3. These signals are selected by the Switch IC 7401
which is controlled by two lines from the Microprocessor, which are SEL-MAIN-R1R2 and SEL-MAIN-FRNT-
RR. If SVHS is the selected input, the Y (Luminance signal) is fed to Pin 29 by 7401. Selected Video or Y from
7301 is output on Pin 54 and is buffered by 7421. If the output of 7301 is Composite Video, the Comb Filter IC
7405 will output Y and C on Pins 15 and 13. Switching IC 7407 selects YC from either the Comb Filter or Y
from 7421. If one of the SVHS inputs is selected, 7401 outputs C (Chrominance) on Pin 14 and is buffered by
7412-B before being fed to 7407. IC 7407 is switched by Pin 22 of 7301. A High on Pin 22 causes Pins 12 and
13 to switch the inputs on Pins 1 and 11. When Pin 22 is Low, 7425 is turned Off switching Pins 5 and 6 High,
selecting the inputs on Pins 4 and 8. Selected YC is then fed to Pins 21 and 20 of 7301 where they are fed to a
Delay Line and Demodulator. The output of the Demodulator and Delay Line is fed to a YUV switch, which
selects between this signal and external YUV (Component Input) from the Jacks on the Large Signal panel.
The selected YUV signal is then fed back into 7301 on Pins 39, 47, and 48. The signal is then fed to a YUV
processing circuit and to an RGB Matrix where OSD (On Screen Display) is added. The signal is then fed to the
RGB output circuit and to the CRT. A Test Waveform is first sent to the CRT on the RGB lines. When this Test
Signal is detected by the CRT drive circuits, the signal is fed back to 7301 on Pin 3 on the CUTOFF LINE.
When these are detected, the Video signal is then output on the RGB lines.