How to solve the display fuse burning repeatedly

Open the display machine does not display, with the Multimeter electric barrier test power line input, resistance to infinity, indicating that the power cord has been open. Power-on check, found that the fuse on the circuit board has been blown, replaced with a new fuse, the boot that burns insurance.

There is a high pressure inside the monitor, although it does not cause life risk, but the taste of electric shock is not easy. Therefore, in the maintenance of the monitor, in order to avoid the high-voltage shock, you can remove the residual electricity in the monitor. The device that can store electricity inside the monitor is the filter capacitor, is that the larger cylindrical components, with insulating layer of pliers to touch the filter capacitance of the two pins, when heard snapped, there is a spark, the filter capacitor inside the electricity has been released, you can rest assured that the inspection. Causes the boot namely burns the insurance several components respectively is the filter capacitance, the degaussing resistance, the row tube and so on.

filter capacitor

Monitors are generally using switching power supply, after the mains access, first through rectification, and then filtered, DC and AC transform, conveying to other equipment use. In order to eliminate and prevent all kinds of interference from the power grid, the electrolytic capacitor must be used for filtering (Fig. 1), and the electrolytic capacitor is connected to the positive and negative pole of DC voltage, which plays a role of DC and AC. When the filter capacitor used for a long time, the electrolyte solidification, easy to cause internal breakdown and short-circuit, so that through the fuse on the current too large, resulting in fuse fuses. As a result, the start-up of the fire insurance, should first check whether the filter capacitor short-circuit, check the method is also very simple, with a multimeter electric barrier, short-circuit capacitor resistance is 0, intact filter capacitor has a charge and discharge process, the resistance gradually increased. The voltage of this capacitor is generally high and can be replaced with the capacitance of the same type of TV set.

There is also a case of failure, is also the boot burn insurance, check the filter capacitor no problem, and in the back of the circuit, and then an infinite capacitor, the capacitance is larger, with a multimeter check found that the resistance is 0, is also the internal breakdown of the failure, after the replacement of troubleshooting.

Degaussing Resistor

CRT display is the operating principle of the electron beam in the picture tube, under the effect of the deflection yoke, the electron bombardment of fluorescent powder on the screen, so that the screen appears corresponding points. The display will be prone to produce magnetic fields, such as multimedia speakers, a variety of peripherals used transformers, these magnetic fields will affect the direction of the beam deflection. Therefore, in order to ensure the display quality, when the monitor is powered on, a degaussing circuit will be set up. Degaussing circuit by the degaussing coil and degaussing resistor composition, through the degaussing coil generated strong magnetic field, can eliminate excitation. Degaussing resistor is actually a thermistor (boxy on the circuit board, there are three pin components, and its cold resistance is generally 12 ohms ~47 ohms, when the mains, its low resistance, degaussing coil electrical work, degaussing coil work current, make degaussing resistance temperature rise, resistance sharply increased, resulting in a sharp reduction of current through the degaussing coil, complete the degaussing process.

From the working principle of degaussing resistance is not difficult to see, when the degaussing resistance of the hot-state resistance to small, or degaussing resistance internal breakdown, the resistance to small, you can think degaussing resistance or damage. can be removed degaussing resistance, with hair dryer heating, its resistance should increase with the temperature increases, if no changes or small changes after heating, you can think degaussing resistance damage. If you determine degaussing resistance damage, you can use the same specifications to replace, if it is not found, can also be a grade of degaussing resistance instead. The degaussing coil is less likely to be damaged and may not be considered.

Row Output Tube

There are several cases of boot burn insurance failure, check the filter capacitor and degaussing resistance are no problem, and finally checked the line output tube, found that the line output tube has been broken short. The line output tube is generally installed on the edge of the row output transformer with three pins. Can be removed from the inspection, if three pins between the resistance is very small, you can think that the row output tube damage, find a similar model for the line.

There are many failures of boot-burning insurance, such as rectifier diode breakdown, power switch tube damage, etc., as long as careful inspection, find fault point, replacement can be. And for the computer room management, there are many generous conditions, the machine room is generally the same model, when the discovery of a machine failure, to find out the suspected fault components, direct replacement, using the elimination method to find the point of failure, replacement components on the line.