Panasonic TC - 230 - d irregular boot after the upper has a shadow, the lower part of the image and a long thin line of superimposed on it (figure 3), as on the extension of time, the shadow gradually -Service Manual Download|Circuit Download|Download Drawings|schematic download|route map download|free download user manual

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Panasonic TC - 230 - d irregular boot after the upper has a shadow, the lower part of the image and a long thin line of superimposed on it (figure 3), as on the extension of time, the shadow gradually

Time：2014-05-28 09:55:58 Source：Network Author：Unknown Clicks：1264

The more exotic failure phenomenon, decided to start from field scanning circuit for maintenance. Check output IC401 (AN5521) and line, field oscillations IC501 (AN5435) peripheral parts were not found abnormal, replacement IC401 and IC501, fault cannot be ruled out. But from the failure phenomenon analysis, a shadow on the screen may have relationship with field blanking signal, and the image of the lower part failure and obvious belongs to the category of the field scan. Try to break the opening blanking signal coupling capacitance C416 (1 mu 50 v/F), the upper part of the screen shadow disappeared, but the lower part failure remains the same (see figure 4) associated circuits. This phenomenon shows that field scanning signal waveform distortion have taken place in. VLfservice manual download site
VLfservice manual download site
Oscilloscope for measured IC401 field driving signal input (4 feet waveform as shown in figure 5, but obvious field in driving signal mixed with high frequency disturbance signal. IC401 (4) feet signal by IC501 pet-name ruby foot to provide, because IC501 and peripheral components have been checked, so will doubt target in Q302 branch. VLfservice manual download site
VLfservice manual download site
In normal work of the TV, figure 4 maintenance switch S301 moving contact in the "N", luminance signal via S301 send to put on a board Y input, at this time in the open circuit state Q302, had no effect on other circuits work. When S301 moving contact seems to "S", to put a plate of luminance signal is cut off, and at the same time Q301 e on the voltage to Q302 b, Q302 conduction, IC40l (4) field driving signal of legs short circuit, level bright line presents on the screen, to adjust the need for maintenance. VLfservice manual download site
VLfservice manual download site
Try to disconnect Q302 c, fault disappear. Check Q302 without exception, oscilloscope for measuring its b pole on a small amplitude pulse waveform. Doubt S30l leakage, causing luminance signal into Q302 b, then through Q302 enlarged with field scanning circuit. VLfservice manual download site
VLfservice manual download site
Remove the S30l, indeed as expected found its "S", "N" side leakage. S30l with anhydrous alcohol cleaning and drying after back to the original circuit, the TV work back to normal.

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