Color decoder chip LA76810A pin function and reference level
Pin number;
1.AUDIO?OUT audio audio output 2.4 volts?
< p>2.FM?OUT audio detection output 2.4 volts3.PIFAGC medium frequency AGC?2.6 volts?
4.RF?AGC high frequency AGC?1.7 volts?
5.VIF?IN1 image intermediate frequency input 12.8 volts?
6.VIF?IN2 image intermediate frequency input 22.8 volts?
7. Place 0 in GND (IF) Volts
8.VCC (VIF) medium discharge power supply 5 volts
9.FM?FIL audio detection filter 2.3 volts
10.AFT?OUT?AFT Output 2.7 volts?
11.DATA data bus 4.7 volts?
12.CLOCK clock bus 4.7 volts?
13.ABL automatic brightness control 3.9 volts< /p>
14.R?IN red characters input 0.9 volts
15.G?IN green characters input 0.9 volts?
16.B?IN blue characters input 0.9 Volts?
17.BLANK?IN character blanking input 0 volts?
18.VCC(RGB)?RGB power supply 7.9 volts
19.R? OUT red output 1.8 volts
20.G?OUT green output 1.8 volts?
21.B?OUT blue output 1.8 volts?
22.SYNC synchronization The signal output is 0.4 volts
23.V?OUT field drives the signal output to 2.2 volts
24.RAM?PALC?FIL field sawtooth waveforms filtering 2.8 volts?
25.VCC(H) row power supply 5V
26.H?AFC?FIL row AFC filter 2.6V
27.H?OUT row push signal output 0.7V
p>28.FBP?IN line reverse pulse input, the sandcastle pulse forms 1.1 volts
29.VCO?IREF line reference current 1.6 volts?
30.CLOCK ?OUT?4MHZ clock signal output 0.9 volts?
31.VCC(CCD)1H-CCD power supply 4.5 volts
32.CCD?FIL?1H-CCD filter 8.3 volts?< /p>
33.GND(CCD/H)?1H-CCD/line oscillation ground 0 volts
34.SECAM?B-Y?IN?SECAM?B-Y input 2.4 volts?
35.SECAM?R-Y?IN?SECAM?R-Y input 2.4 volts?
36.APC2?FIL?APC2 filter 3.7 volts
37.FSC?OUT load wave output 2.2 volts?
38.XTAL4.43MHZ crystal oscillation 2.7 volts
39.APC1?FIL?APC1 filter 3.4 volts?
40.SELEC?V?OUT video selection output 2.1 volts?
41.GND (V/C/D) video /Chroma/Deflection circuit ground 0V?
42.EXT?VIDEO?IN External video signal/Y signal input 2.4V
43.VCC (V/C/D) Video/chroma/deflection circuit power supply 5V?
44.INT?VIDEO?IN internal video signal/C signal input 2.7V
45.BLACK?STR?FIL black power Flat extension filter 3.1 volts?
46.VIDEO?OUT video signal output 1.8 volts
47.VCO?FIL IF PLL loop filter 3.4 volts
48 .VCO?COIL image demodulation oscillation coil external terminal 3.2 volts?
49.VCO?COIL image demodulation oscillation coil external terminal 4.2 volts?
50.PIF?FIL image intermediate frequency APC external filter terminal 2.3 volts
51.EXT?AUDIO?IN external audio signal input terminal 2.2 volts
52.SIF?OUT second audio intermediate frequency signal input terminal 2.1 volts?
53.SIF?APC?FIL audio demodulation APC external filter terminal 2.2 volts
54.SIF?IN second audio intermediate frequency signal input terminal 3.1 volts
Why are there no color TV stations?
(1)∠ACG=∠ABH=∠GAH=45°,
∠GAC=∠AHB=∠AHC , so △AGC is always similar to △HAB and △HGA
(2)CG/sin∠GAC=AC/sin∠AGC=4/sin∠AGC, CGsin∠AGC=4sin∠GAC
BH/sin∠BAH=AB/sin∠AHB=4/sin∠GAC, BHsin∠GAC=4sin∠AGC
Multiply the two equations to get xy=16
(3)BC=4√2, GH=BH-(BC-CG)=BH+CG-BC=BH+CG-4√2
When DF and AC coincide, △ AGH is an isosceles triangle, at this time x=2√2
When the bisector of ∠GDF coincides with the bisector of ∠BAC, △AGH is an isosceles triangle, at this time x=4-2√2
What is the function of AGC in the circuit?
If the station is not saved, it should have nothing to do with AGC. Being able to search for stations with good effect means that there is no problem with AGC.
There is no channel fault. I think 98% of it is caused by mid-week detuning. 2% are caused by other faults, such as a bad memory, etc.
Generally speaking, adjustments need to be made when changing to mid-week, and it is not a matter of just changing. Use a small screwdriver to adjust the magnetic core in the middle circumference, 10 to 20 degrees at a time, adjust it once, and automatically search for channels once. Take out the screwdriver when searching for channels. An experienced user can adjust the magnetic core with a non-inductive screwdriver made of copper or aluminum, preferably plastic, while automatically searching the station.
AGC is automatic gain control. Its function is to automatically control the amplification factor of the signal. That is, when the tuner receives a weak signal, it will automatically control the amplifier tube to increase the amplification factor, and vice versa to decrease the amplification factor. The circuit that implements this function is referred to as the AGC circuit. The AGC circuit is a closed-loop electronic circuit, which can be divided into two parts: a gain-controlled amplification circuit and a control voltage forming circuit. The gain controlled amplification circuit is located in the forward amplification path, its gain changes with the control voltage, and the gain automatically adjusts with the signal strength.
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