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5TYservice manual download site
By IC3001 15} {C signal output, foot PAL4.43 MHz chroma by IC601 49} {into the feet, through IC601 demodulation R Y, B Y signal, respectively by {40}, {41} feet output, sent to 1 h delay line IC603 (TA8772AN) {27}, {} 26 feet. Approved by IC603 process, and the delay of 1 h R Y, B Y signal from {30}, {29} feet output, return IC601 {37}, {38} foot, then the color difference within IC601 matrix circuit to produce the G Y signal. 5TYservice manual download site
The image sharpness of circuit and artificial intelligence level to enhance the brightness of the signal processing circuit by IC601 {} 60 feet input, further processed within IC601 sent to IC internal gezer matrix circuit, and R - Y - Y, G, B - Y color difference signal demodulation with the R, G, B primary signal, and then by the {16}, {} 17, 18} {the feet, output to IC3401 (TA8889AP) {1}, {3}, {6} feet. IC3401 white balance adjustment circuit for I2C bus control, adjusted the R, G, B signals by {16}, {14}, {12} feet output, sent to the final visual circuitry IC351 (TDA6103Q) {1}, {2}, {3} foot, after amplification by {9}, {8}, {7} feet, output to tube cathode. 5TYservice manual download site
It seems that the video signal through the path is more, to accurately determine where the video signal causes the loss of the high frequency component is not easy. But noticed that in this case, the fault is accompanied by the image quality and brightness of variation phenomenon, and the change of the brightness, is bound to appear in some relevant points of dc potential changes, from finding the cause of tube brightness down, perhaps can more easily find out the cause of the problem. 5TYservice manual download site
Repair process: according to the above analysis, first check to supply the machine small signal processing circuit on the 9 v, 12 v voltage, in no change before and after failure occurs, ruled out of the cause caused by poor power supply. 5TYservice manual download site
Then measure the IC351 R, G and B outputs {7}, {8}, {9} foot voltage, found after failure occurs, the voltage 160 v respectively by normal up to 202 v, 197 v, 197 v. Because IC351 {5} feet for reference voltage sampling, the terminal voltage change will also affect the R, G, B the output dc voltage change at the same time. Therefore, monitoring IC351 {5} feet voltage, no change before and after failure occurs, the next step test IC351 dc voltage at the input. Because of its {1}, {2}, {3} feet and IC3401 {16}, {14}, {12} feet for dc coupling, to shorten the maintenance time, directly measuring IC3401 {12}, {and}, {16} feet of voltage. Just boot, IC3401 three feet above the dc voltage is 2.67 V, 2.85 V, 2.67 V respectively, as the extension of boot time gradually reduced to 2.10 V, 2.17 V, 2.31 V, the input {1}, {3}, {6} foot dc voltage is from 2.10 V, 2.10 V, 2.23 V to 1.70 V, 1.69 V, 1.69 V. For IC3401 {1}, {3}, {6} feet and IC601 {16}, {17}, {} 18 feet straight through, and IC601 dc voltage at the input changes may also influence the output dc voltage change, therefore, measuring IC601 R Y, B Y the input {37}, {38} feet voltage, stable without change. You can see by the appended drawings, IC603 no dc coupled with IC601, therefore, its pin dc voltage does not influence each other, but in consideration of the input signal amplitude IC601 whether changes will also affect the change of its output dc voltage, so the oscilloscope for monitoring IC601 {37}, {38} feet signal waveform, its amplitude has no obvious change before and after failure occurs.
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