Indicates whether the machine tuning circuit is implemented by IC7921 in 1910 and its peripheral circuits. The circuit has 5 inputs: (1) 0~30V tuning voltage, add to IC7921 black-foot, (2) recognition signal from IC7875 13 feet, add to IC7921 h foot; (3) sand Castle from IC7875 17 foot pulses, adding to IC7921 four feet (4) switching voltage, from line switch YHFa voltage
6923 to diode cathode (5) YHFb voltage is applied to the diode 6924 cathode.
Output end has 3 a: (1) transistor 7925 launches very DC voltage by resistance 3938 to decoding Board 1200 Terminal ⑥, for elimination hidden channel digital; (2) in YHFa segment Shi, transistor 7925 launches very output of tuning line pulse by diode 6925 sent to decoding Board 12000 sadly feet; (3) transistor 7925 shot very output of tuning line pulse, by diode 6922 sent to decoding Board 1200 ⑧ feet.
VHFa snippets, 6923 diode conduction, diode 6922 globe, 6925 tuning line pulse diode, resistor 3939 to IC7292 red base color and amplifier, it displays a red bar. When in the YHFb band IC7925 tuning line pulse output, 6922, resistance of the diode 3940 to Green primary amplifier, so show the green bar, UHF segment, diode 6923,6924 globe, diode-6922. 6925 turn-on, so show the yellow bar.
Because no colour tune VHF only a line instructions, mainly by 7925 emitter output to decode IC7292 13 tuning line pulse input blocked. 6925 damage is found upon examination, so no colour tune line.
When resistance capacitance 2238 3939, when open, no red line when the resistance, diode 6923 3942 when open, VHFa segment indicates whether the line is yellow; when the resistance, diode 6924 3941 when open, VHFa leader line turn yellow when 2239 3940 6922, resistance, capacitance of the diode when open, YHF b-segments with direct line.