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Analysis and Maintenance: Based on the fault phenomenon, it is preliminarily judged that the fault lies in the small signal processing circuit of the field scanning. The causes of this fault are analyzed as follows: (1) No composite synchronization signal or insufficient pulse amplitude. (2) The internal synchronization separation circuit of TA8659AN is damaged, leading to the loss of synchronization signal. According to the above analysis, the DC potential of pin 33 (composite synchronization signal) of TA8659AN is found to be lower than normal. It should normally be 6.2V. Upon checking the related peripheral components R343, C315, R337, C314, it was found that R337 has changed value.
Solution: After replacing R337, the fault was eliminated.
Source: Beijing Konka TV After-sales Service Phone http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3761213.
Maintenance Tip: If the external circuit connected to pin 33 of TA8659AN works normally, a 2.2uF capacitor can be used to directly couple the color full TV signal from pin 30 of TA8615N to pin 33 of TA8659AN. If the fault disappears, the TV/AV switching circuit and Y/C separation circuit's brightness channel should be checked carefully. If the fault still exists, the voltage of pin 30 of TA8615N can be tested. If it is 2.8V, it usually indicates that TA8659AN is damaged. Otherwise, TA8615AN and its peripheral circuits should be checked. - Beijing Konka TV Repair Center.