Saturday, December 18, 2010

【 Weak current College 】 line pipe breakdown of causes in line pipe breakdown causes classification 】

1. switch the power supply output voltage too high

Due to the power supply voltage regulation system fails, not regulators, led to B + voltage to rise. If B + voltage exceeding 10 per cent, will produce line tube puncture damage to the phenomenon. You should focus on check sampling error amplifier circuits, and PWM control circuit components. In addition, if the voltage is too high, exceeding the power supply voltage range of values allowed, can have a switching power supply output voltage is too high.

2, the second supply voltage circuit exception, leading to the second power supply is too high

Normally, the monitor is powered on, due to the presence of slow startup circuit, B + voltage is slowly rising, not power on after the jump to high voltage. If slow start capacitor failure tolerance of corruption, it will cause a post immediately jumped when voltage, voltage instability, easily burn line pipe.

Also, the second supply sample voltage-stabilizing circuit components and for damage, will make people second power supply exception.

3, row, row output deflection yoke or partial short-circuit

Line deflection coil 奩 line output transformer insulation wire fever after performance and produce local short-circuit protection circuit performance, if not better, you can cause damage to the pipe line. This can be used with the same model compared to normal machine, by measuring the output-current. If no moment immediately burn line pipe, fingered heatsink temperature is high, the deflection yoke is row or rows of the output transformer short circuit, overcurrent breakdown due to line pipe.

4, row frequency too low

For flowed line deflection coil current maximum value and the line is proportional to the range scan time, that is, the lower row frequency, cycle length, row range time corresponding variable-length rows, with the result that, when the deflection current rise over line pipe on the current maximum value, use the line tube burned. Therefore, when you resize the row frequency, avoid using row frequency long low status. Display row frequency is determined by the rows field signal MCU detection, according to the display mode of the automatic switching, and generally do not appear row frequency too low.

5. line backward time too short

In line backward, produces very high anti-peak pulse voltage, this requires line backward capacitors, output tube, such as damping diode components have a very high pressure resistance. When rows backward capacitor size smaller, failure or open circuit, the peak pulse voltage rise once more than line pipe pressure value, line pipe for a roasted a result. In this case, swift fingered line pipe of the heat sink, if temperature and not pre-boot almost, because backward capacitance open circuit and over voltage breakdown.

Solutions: are all the rows backward Capacitance to be renewed.

6, row, insufficient incentives

If the row is not enough incentive, line pipe is not rapidly saturated, causing the line pipe internal resistance of the larger, use line scan linear variation; if the row is not enough, the tubes motivation cannot quickly due to the use of line pipe for a long time in a current flow through the State of not working properly, will cause the output circuits of power consumption increases, causing a line output tube perm. Once the above line pipe power consumption limits, you will use line tube again burned. The time interval is fast with slow, or post on the firing line pipe; some time before firing line pipe. If the interval length, not-for-oscilloscope observation of incentive to help find the waveform of the cause of the failure.

Result row causes of insufficient motivation are: poor performance incentive pipe line; line incentive power supply transformer resistor increases; row of around encouraging transformer components are soldered; row primary incentive transformer on the burning group filter capacitor metamorphic; line oscillation circuit oscillator bad; IC power oscillator circuit separate rows in the foot of the external capacitor failure caused adverse. filtering

7, environmental humidity

This uses the output transformer leakage around the component, or because of the heat (such as the TV is placed in the Cabinet, or repair line pipe and heat plate retention screw is not tightened), line tube overheating to pressure reducing and eventually result in damage to line pipe.

8, row deflection coil-circuit

This time line scan is the second half of the rows Cheng tube breakover time will be greater than the cutoff time, use the line pipe in the backward on-time, causing the line short tube is damaged. Therefore, the maintenance to be extra cautious when, in the line of deflection coil loop open circuit, if long power maintenance is extremely dangerous.

9, line scan circuit components exist instability or aging, the damage to the circuit.

If S calibration capacitor short-circuit, pillow school circuit elements, so that the line current of short circuit, causing line pipe for flowed and breakdown.

In addition, damping, bootstrap diode with open-circuit voltage boosting capacitor short-circuit, electric breach (such as high-voltage spark, high perforation), line pipe quality is poor, CRT internal Flash, AFC circuit failure, etc., will cause line pipe over current breakdown.

10, switching power supply line pulse signal coupling capacitors, sampling filter capacitor voltage tolerance lost.

In the vicinity of high temperature baking high power components, the capacitor failure tolerance, lead line tube puncture.

11, parcel (FBT Flyback transformer) or row Center adjust coil, pillow-transformer, line pipe, backward diode, pin soldered

Virtual welding is a monitor component damage the enemy, switching power supply transformer, power management, line pipe, parcel, backward diode, capacitor, line backward to adjust the coils are work centre in high-current, high voltage environment, the virtual welding will cause instant-on and voltage cutoff, Spike easily burned power tubes and line pipe.

12, line pipe model wrong or line tube amplification much difference, or use the built-in damping diode or damping resistance of line pipe

We measure line scan circuit, key point voltage is also a need to pay attention to measuring method, if improper measurement method will instantly burn line pipe.

13, high-voltage spark, also contribute to the line pipe damage the cause of a

High voltage package in use after three to five years, due to the ageing of insulation, prone to highPressure from striking phenomenon. High-voltage spark may occur in high pressure inside the package, or it may occur in high voltage package on Earth, it may also be high pressure nozzle.

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