How to check the monitor backlight

The crystals of which the screen is made are capable of polarizing a beam of light passing through them. If you change the voltage applied to the liquid crystal, you can adjust the degree of its polarizability, which means the color into which it can "turn" the beam of transmitted light. From the reflected rays, multi-colored dots are obtained, which are collected in an image. Checking monitors is the first item in calculating problems.

All liquid crystals are collected on an LCD matrix with thin-film transistors. This matrix “glows” makes the lamp - a source of light that will polarize in the crystals.

NOTE! Despite the fact that several lamps (sometimes 4-6) can stand at the top and bottom of the screen for illumination, the image disappears even if one of them fails. Protection works on the inverter controller and turns off all at once.

If one of the following problems was discovered by you:

• the screen goes out;
• half of the screen went blank;
• half of the screen began to glow more dimly;
• half or the entire screen glows pink;
• the monitor turns on, it works for a few seconds and the screen goes blank.

You can independently check the lamp operation and find a malfunction.

INTERESTING! If the warranty is valid, we recommend using it.

What tools are needed to disassemble the monitor

IMPORTANT! If possible, entrust the repair to professional craftsmen. If this is not possible - proceed on your own, but taking the security measures listed below. If you violate the process technology, you may suffer! And the procedure itself is long and laborious.

You will need:

• serviceable backlight;
• soft cloth on which to lay the screen and not scratch it;
• magnetic screwdrivers with different bits (flat and cross);
• multimeter (tester);
• oscilloscope;
• scalpel and tweezers.

Instructions on how to disassemble the monitor

• First of all, you need to lay out a soft napkin at the workplace and put the monitor face down on it.
• We remove the monitor stand and the plastic cover by unscrewing the fasteners, if necessary.
• The monitor is turned over, the front frame, which usually rests on plastic latches, is removed.
• The power supply, which is installed at the bottom of the matrix, is disconnected and removed. Carefully disconnect the cable and remove the power supply board. To disconnect the cable, you need to lightly press the holders with one hand, and gently pull out the cable with the other.

ATTENTION! In monitors with LCD backlight, high-voltage inverters with a voltage of 1000 volts are installed! Trying to touch this part with the monitor turned on can end very regrettably. An attempt to touch any other metal part of the monitor may result in a noticeable shock due to the remaining charge remaining on them.

• To access the lamps - you need to disassemble the screen. To do this, remove the metal frame and then the LCD panel, plate and film are laid out in the correct order on a soft cloth.
• The reflective substrate is removed, the edging is removed from the lamps.

The monitor is going in the reverse order.

ATTENTION! Violation of safety precautions entails severe electrical injuries, burns, mechanical damage. Before starting work, the technician must stand for several minutes turned off from the network so that the capacitors can discharge.

How to check the backlight

There are several ways to do this:

• ring with a multimeter. Measuring the voltage at the inverter outputs with a tester is a sad fate for the tester. He will burn;
• check with a single-tube inverter;
• replace the lamp with a known working one;
• compare with an oscilloscope the voltage levels at the cold ends of the lamps;
• check with capacitors.

ATTENTION! The problem may not only be in the lamp. A power supply unit, an inverter, and a PWM controller can fly - anything. If you are not confident in your abilities - do not take up the job and do not break the poor monitor.

The most important thing when replacing the lamp is to turn off the protection on the inverter. Each inverter model has its own operation algorithm, so you need to look specifically for the model being repaired.

Let's analyze one way to check. The simplest is testing with a suitable working backlight. If the screen works with a new lamp and produces a bright image - the problem is in the lamp. If not, it’s the inverter, the loop, or you need to dig deeper and change the matrix or circuit.