The microcontroller circuit LA76810 , line scan from the small- signal circuit ( 25 ) ( 26 ) ( 27 ) ( 28 ) ( 29 ) ( 30 ) # composition, ( 25 ) # is +5 V power supply line scan , ( 26 ) for the line the phase of the filter circuit , ( 27 ) the line pulse output pin ( 28 ) for row # feedback input pulse ( 29 ) ( 30 ) # is the line oscillator timing signal and the horizontal synchronizing pulse signal line for the internal phase obtained comparison , the filter circuit, the error voltage derived from the line of the phase of the oscillation to control the line , after the ( 27 ) # output driven by V431 T431 , added to the line pipe V432, sawtooth deflection coil on the control line CRT complete the scan. On the line flyback pulse is applied to draw the line output transformer high , medium and low voltage supply tubes each pole and other circuitry.
TV does not boot no raster, no sound failure , possibly in the power circuit or line scan circuit , causing the power supply does not work without power . We inspected according to the following ideas .
The first step: measuring the switching power supply 130V secondary output is normal, if normal fault line scan , if there is no 130V, 130V can disconnect the power supply to the line of resistance , access dummy load . With 220V, 60W bulbs 130V output of one end , the other end of the ground . Powered light bulb as measured simultaneously 130V normal, fault line scan circuit . Power lamp is not lit , no 130V output measurement , fault in the switching power supply, ( how overhaul in switching power supply in one focusing on the switching power supply)
Step two: determine the fault line scan measurements can be added such as 130V line pipe collector , first -class failure . We can use a multimeter to measure AC voltage profile 10V line drive transformer secondary has no AC voltage , and if so, the fault line output. If not, check the promotion level . Line drive circuit is more prone to false welding failure, should pay attention to maintenance. If the line to promote normal , we continue to check the front-end circuit .

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