Fault time within a clear "chirp" sound, after a few seconds chirp disappear; Boot up again after a while, the television can work again a minute or so, after the failure again. 53Tservice manual download site
 53Tservice manual download site
As there is no fixed bracket the machine circuit motherboard, motherboard prolapse, combined with the components on the pin tin quantity is little, so prone to pin cracks and pin desoldering. According to failure phenomena, the first suspect line contact undesirable, found components foot has obvious crack inspection, but after repair welding failure remains. As shown in the appended drawings, with digital meter to monitor the main power supply voltage 113 v, the television work normally when the voltage is normal, failure occurs when the voltage over chirp in around 50 v flashing, also found that chirp from T801 switch transformer. 53Tservice manual download site
 53Tservice manual download site
 53Tservice manual download site
A chirp, the switching power supply can work; To judge fault range, line will load disconnect, on 113 V mains connected to 60 w incandescent bulbs do dummy load, boot monitoring the output voltage of 108.7 V, and is very stable. Because the line output circuit does not work, because of no line flyback switch power supply impulse to join with the line frequency synchronization, and make the output voltage is lower than normal slightly, based on past experience, judgment, switching power supply is normal, fault could line load or protection circuit. The machine protection circuit is relatively perfect, in addition to the power protection circuit, it is also equipped with the following protection: 1. The line flyback voltage over-voltage protection; 2. Line output transformer short-circuit protection; 3. The beam current over-current protection; 4. The field output over-current protection; 5. The output load protection. 53Tservice manual download site
The above five kinds of protection are by R536 IC601 (AN5601K) {42} JiaoHang oscillation power controls. Since did not see figure abnormal sound when failure occurs, so doubt protection circuit misoperation. Try to R536 disconnect, fault phenomenon remains the same. Thus suspect line output part of a component is soft breakdown phenomenon, in turn, the substitution line pipe, flyback capacitor, output transformer, a large number of components such as the fault failed to rule out, repair in trouble at the moment.

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