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JVC 2588 color TV after three no lightning

Time£º2017-04-13 08:06:19  Source£ºNetwork  Author£ºUnknown  Clicks£º1469
  

JVC 2588 color TV after three no-shot, the machine work in the standby mode by lightning, once again boot red light does not shine, there is no phenomenon. According to experience to determine the lightning current from the power line into the breakdown of the power part of the device caused by the machine can not work. Open the machine check found 3.15A fuse has been blown, STR6708 thick film block ¢Ù ¢Ú ¢Û feet internal switch tube has been breakdown, Q901 breakdown, R917 open circuit, the other no obvious breakdown phenomenon, the above damaged components connected to disconnect the L921 line load C924 two ends and then 100W cannon fake load, boot light bulb. Measured voltage of 27V, indicating that the power part has started, the machine work in standby mode. With the remote control boot, the bulb shiny voltage is 135V normal, but found R925 smoke, C708 burst, speed off. The machine without circuit diagram, according to self-mapping schematic diagram analysis, C708 pressure 16V, the burst instructions added to the higher voltage at both ends. Under normal circumstances, CPU17 pin output high, Q924 conduction, Q923 cut-off, Q925 cut off, the power supply work, the regulator part of the IC921 output voltage control optocoupler light-emitting diode luminous intensity to stabilize the output voltage, while the CPU17 output High voltage Q927 conduction, Q926 conduction, D922 rectifier, C926 filter into the 10V voltage through the Q926 added to 1C201 ¢á and IC981 regulator into the 5V output to the machine work, this time the CPU voltage from the D922 rectifier, IOV Voltage by IC704 regulator reset regulator output 5V voltage added to the CPU ¢Þ pin, the reset voltage to 29 feet to make the CPU work properly, standby CPU17 pin output low to Q924 cut off, Q923 conduction, optocoupler ¢Ú pin voltage drop , The internal light-emitting diode luminous intensity increases, so that optocoupler ¢Û feet within the small resistance, switching pulse width decreases, + B voltage dropped to 27V or so, this time D922 rectified output voltage has dropped to 2-3V, can not maintain the CPU normal work , The CPU operating voltage has been changed by D924 rectified output 10V or so voltage through the conduction Q925 continue to provide. According to the above analysis. C708 burst is due to Q925 work in the machine is not cut off the results, check the 0925 has been punctured, the Q925, C708, fC704 after the start-up detection standby, work output voltage is normal, remove the lamp connected L921 start sound normal, fault exclude.3iyservice manual download site