Trouble Shooting of Panasonic TV Protection Circuitsx7service manual download site
 As the protection of the Panasonic TV implementation circuit and on / off circuit connection, the protection of the control circuit is the main switching power supply, protection and standby state similar. If the relay has a relay pull the sound and reaction, but can not boot, the indicator light from yellow to red, but can not turn green, and then release the relay, or boot after the remote standby operation, the TV automatically shut down, the light from the Turn on the green into a red or yellow can be judged to protect the circuit work, into the protection of the state.sx7service manual download site
 2. Measure the key voltage to determine the fault rangesx7service manual download site
 (1) to determine whether to enter the protection statesx7service manual download site
 (6) pin voltage and standby control pin (33), and the ICL213 (6) pin voltage and standby control pin (33) are measured when the main switch power is turned off, Pin voltage, if (6) the foot voltage from the normal low level into a high level of 2.5V or more, while (33) pin voltage from the boot when the high level into a low level, you can determine is to enter the protection status.sx7service manual download site
 (2) to determine which protection is caused by the protection circuitsx7service manual download site
 If the D819's positive pole of the light-emitting diode (point A in the figure), the base of Q856 (point B in the figure) will be measured when the protection voltage of each circuit protection circuit and the microprocessor's fault voltage will be measured. Q858, Q858, Q858 (Figure A, B) has a trigger voltage while the microprocessor interrupt is also high, is the separation component protection circuit caused by protection; if the protection of the implementation of the circuit D819, Q856, Q858 (Figure A, B , C point) no trigger voltage, but the microprocessor interrupt level is high, it is caused by the interrupt port circuit protection. If the D819, Q856, Q858 (A, B, C points in the figure), which way to protect the implementation of the circuit has a trigger voltage, you can determine the protection of the circuit to start, causing protection.sx7service manual download site
 (3) to determine which fault detection circuit is caused by the protectionsx7service manual download site
 The output voltage of the fault detection circuit connected to the protection execution circuit is measured before determining the protection caused by the activation of the circuit protection circuit, and the D, E, F, G point voltage in the drawing is measured and the detection circuit output High level, it is the detection of the circuit or the detection circuit failure.sx7service manual download site
 3. Remove the protection, observe the fault phenomenonsx7service manual download site
 In order to ensure the safety of the Panasonic TV, to avoid unnecessary damage caused by the lifting of protection, it is recommended to lift the protection before the first three measures:sx7service manual download site
 First, remove the mains full-wave and voltage rectifier automatic switching circuit IC895, to full-wave rectifier circuit to avoid the automatic switching circuit failure or malfunction caused by damage to the power components; Second, the measurement power and line output circuit no obvious short circuit, open Fault, power thick film block and row output tube intact; third is the first off + B load, then leave the load test machine, + B voltage is normal, and then restore the line output circuit for maintenance.sx7service manual download site
 Since the discrete component protection circuit of the Panasonic TV is not detected and implemented by the microprocessor interrupter, the protection of the discrete component protection circuit can not be lifted by the implementation of the breakout and can be protected by the following methods:sx7service manual download site
 (1) from the standby circuit to take measures to lift the protection statesx7service manual download site
 There are two ways: First, the standby control relay RL801 switch contact short circuit, directly for the main power supply; Second, the Q852 base through the resistor + 5V secondary power supply, while disconnecting the R854, so Q852 forced conduction, RL801 suction Together After forced power, observe the fault after power supply, measure the relevant voltage, according to the fault phenomena and voltage to determine the fault range. At this point because the microprocessor is still in standby mode, can not output the control voltage, may produce no light, silent failure, but the switching power supply and related circuits for preliminary testing.sx7service manual download site
 (2) from the protection of the implementation of the circuit to take measures to lift the protection statussx7service manual download site
 There are short circuit and open circuit two ways: First, one by one short circuit protection circuit to implement the trigger voltage, that is, one by one D819 light and cathode diode short circuit, the Q856, Q858 between the base and ground short circuit, the D553, D862 Of the positive and short circuit; Second, one by one to disconnect the protection circuit and standby control circuit connection, or directly remove the protection of the implementation of components.sx7service manual download site
Every short circuit or open a protective actuator, a boot test to observe the fault phenomenon, the test, if the trigger voltage or remove the protection of the implementation of the circuit, the TV is no longer protected, it is the protection of the implementation of the circuit caused by protection, according to Exit the fault after the protection of the phenomenon, to determine the scope of failure for further maintenance.sx7service manual download site