Author£ºUnknown
Source£ºNetwork
2015-07-05 08:05:58
Core tips£ºTC-43P18G color Panasonic Diantong boot three
Energized to watch the boot, found in alternating current (AC) connected to the moment, the green indicator light flash is destroyed, red lights flashing and accompanied by a relay and acoustic release. This phenomenon shows that the color TV by the ON way to protect the standby mode OFF. First try to switch the power of a circuit in the protection of resistance R817 disconnect, and found that the protection of standby state. Measuring the DC voltage of the rectifier filter for normal +298V suspected rectifier voltage over-voltage protection circuit fault caused by malfunction or power on / off mode conversion control circuit action (such as shown in the figure). This circuit is composed of Q856, Q852, RL801, relay IC1213 and Q857 (33). When the AC power is connected, the auxiliary switch power oscillation produced STBY+12V DC voltage, the IC1212 adjustment of the regulator as the main control CPUIC1213 and eep-rom memory IC1211 provide power STBY+5V.IC1212 active low reset signal of reset chip IC1214, of the system is reset to zero, the IC1213 is (62), (63) foot 8MHz clock signal is stable and high level of given the.IC1214 4.9v abolished signal voltage of the CPU and the redeployment of a time before shutdown program data. From the IC1213 is, the feet (33), output a power high signal, enable 0852 guide through, the relay RL801 pull, the main switching power supply are +298V rectifying filtering voltage oscillation.
In the remote control on the "power" button is pressed, the pin (33) of the main control CPUIC1213 turn to a low level, the deadline 0852. Release relay RL801, cut off the input AC mains power. Also, the IC1213 is from (40) pin output low level, the cut-off Q1003, two-color diode D1004 C tube extinguished, R tube light, indicating main power into off standby mode. Low polar C-E immediately and can not guide.D820 cathode to the pressure detection of, and resistance +298V IC801, and R843,,, and diode, Zener voltage over-voltage protection circuit is composed of a photoelectric coupler D819 D820 R816 r817 r818 d821 ot-c825 composition, after rectifying and filtering to DC pulse voltage, the R816 r817 r818 and D820 machine normal work, when the voltage is increased to protect the threshold, a voltage stabilizing diode D820 avalanche breakdown conduction, photoelectric coupler in light emitting diode conduction, luminous intensity increases, the secondary photosensitive tube resistance decreased, Q825h pole level of cut-off relay release, cut off the main AC power supply into the protection of the state. D819 the Q857b pole voltage is also reduced and the conduction, the C current through the D859 excitation to make Q856 saturated conduction. At the same time, Q857 conduction after the very C high level protect signal feedback to the IC1213 is feet (6), the main control CPU detection to protect high level signals, then immediately issued a directive on the protection of and standby protection lock, so as to avoid the main power to stop working after the D819 flip, cause the relay repeated release and pull and damage to the contacts. Check power ON/OFF mode converter control circuit is not found, then check the voltage of the rectifier voltage protection circuit related components, found that the voltage regulator diode D820 has been breakdown. After the replacement of D820, troubleshooting.