What is the reason that the monitor has no image

The monitor just opened the machine all normal, but after a while there is no grating, no image, and a slight squeak issued. From the phenomenon of failure, the display is a failure of instability. Using the cooling method and heating method to check all the main circuits of the display, the problem is found, and then the following check:

(1) Check the power output voltage (90V) is normal, the result is ov, which indicates that the power supply may be faulty, but also may be the main load has short-circuit the place. Any of the two problems exist, will cause the switching power supply output voltage is ov, that is, the power supply without output voltage. But because there is squeak, the power supply has been oscillating, but the frequency is abnormal, you can think that the power supply is basically normal, should focus on checking the load circuit.

(2) The line output transformer and the power supply voltage line cut off, measuring power output voltage of 90V normal, indicating that the fault is really out in the load circuit, and the line output circuit is the main load, it is likely that the line output circuit short-circuit.

(3) Inspection line output tube, line output transformer and other components, are intact, no breakdown short-circuit phenomenon, why as long as the uplink load failure occurred, and check the load circuit did not find the breakdown of the components.

The analysis is estimated for two reasons: one is in the high-pressure pulse state, the row output tube, the line transformer some kind of insulating material is breakdown to form the short circuit; the second is 90V power supply to the line output circuit of a certain part of the insulation resistance, resulting in a similar short-circuit phenomenon, the above two points with a multimeter is not checked out.

(4) Using the method of changing parts, the first line output tube set electrode and the heat sink between the mica plate with a new replacement. Boot test, troubleshooting.