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Фрагмент инструкции
The 1 st and 2nd square are PAL coded. This section indicates the proper functioning of the color demodulator part. The third section consists of four squares which are color coded but should not show any color at a well aligned color television or monitor: all four squares should be grey. Both R-Y squares are NTSC coded: the R-Y signal does not change direction 180° each line. The burst signal is PAL coded and ensures normal operation of the PAL switch in a color receiver. The third and fourth square contain only B-Y signal information, alternating 180° each following line. Delay line check: The third part of the pattern is designed for alignment of the 64 [is chrominance delay in amplitude and phase. ’Venetian blinds’ appear when adjustment is needed. It is possible to distinguish between amplitude and phase faults by noting in which bars these blinds appear. Since the R-Y signal in square one and two are NTSC coded, the delay line and PAL switch should eliminate all R-Y information since this information in successive lines of the first two squares is being subtracted. When an amplitude error exists between direct and delayed signals, the subtracter output of the delay line will produce R-Y information in one and two. The action of the PAL switch will cause the information to be inverted on alternate lines to give the Venetian blind effect. When a phase error exists between direct and delayed signals, Venetian blinds will show up in squares three and four. Additionally, they also will appear in the yellowish horizontal bar (G-Y = 0) of the upper left section of this test pattern. (GB) 3-14 OPERATING INSTRUCTIONS PM 5414 V Demodulator check: This pattern can also be used to pick upfaults in another important part of the color TV, the demodulators. The subcarrier frequency should be applied to the R-Y and B-Y demodulators in the correct phase; otherwise, all four squares will contain color. When the phase of the subcarrier fed to a demodulator is correct, the R-Y demodulator will only demodulate R-Y information, and the B-Y unit will only demodulate B-Y information. When the subcarrier frequency has a phase difference, this results in R-Y information passing the B-Y demodulator in squares three and four. Similarly the R-Y demodulator could receive B-Y information. Then this will be seen as a color information in square one and two. So a phase error in the subcarrier at both demodulators (that is, a general phase fault) causes both to pass incorrect information. The fault shows up a color in all four squares. A phase fault confined to the 90° phase-shifted subcarrier will only cause one demodulator to pass incorrect information. This fault will cause color either in the first two or last two squares, depending on the type of receiver. 12. Purity with a choice of the three primary colors clearly indicated by LEDs. The red pattern is used for checking color purity. In a correctly adjusted receiver, each electron beam will strike only one set of color dots or stripes on the screen. Only this color should be visible; the presence of any other color is an indication that color purity needs adjustment. The green pattern provides a purity check for three in-line tubes. Blue is also available to check color performance. The three complementary colors, magenta, yellow, and cyan can also be displayed by combining the respective primary colors. These patterns can also be used to ensure that there is no interference between the sound and chroma carrier. And because the pattern has a 75 % saturation setting, it can be used with VCRs to align the writing current of the chrominance signal. In addition to the primary and complementary colors, 100 % white can be selected as well as black which contains no video information to check, for example, the front and back porch of the synchronization pulses. PM 5414 V OPERATING INSTRUCTIONS (GB) 3-15 3.5.9 Video Signal The video signal (CVBS) generated by the instrument is available at the BNC socket VIDEO OUT. The signal is also available at the Scart connector AUDIO/VIDEO OUT, pin 19. The amplitude of the video signal is 1 Vpp into 75 £2 with the VIDEO AMPL control in stop position ‘1 V’; it can also be set from 0 to 1.5 Vpp. The chrominance signal within the CVBS signal and the subcarrier sync signal (color burst) is fixed to 100 % and can be turned off by pressing the CHROMA OFF pushbutton. 3.5.10 Synchronization, Triggering Fortriggeringofthetimebaseofan oscilloscope, respectively a waveform monitor the pattern generator feeds a composite sync signal to the LINE/FIELD SYNC OUT connector. The amplitude (open circuit) of the line sync pulses is 2.6 Vpp, while it is 5 Vpp for the frame pulses. By means of the trigger signal a convenient synchronization of the V- and H-signals is possible. 3.5.11 Y/C& RGB Unit Modern video instruments can directly be controlled via Y/C respectively RGB signals. Using higher bandwidths in the transmission path results i...
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