Common Problems with LCD Projectors and Their Solutions

Liquid crystal ( LCD ) projection technology is one of the mainstream digital projector display technologies. With its irreplaceable large screen advantage, projection imaging technology has become the best technical choice for movie projection, home theater applications, business meetings, education and teaching, large-scale command and control, and monitoring display systems, and plays a huge role in all aspects of national life. As one of the most mainstream technologies of modern digital projection, LCD projection products are very popular among users.

From a technical perspective, the rise of LCD projectors is mainly due to an extremely critical component inside LCD. Originally, large-screen projection was mostly based on the use of traditional CRT-type three-gun projectors, but after the 1990s, due to the breakthrough in LCD mass production technology, the resolution and brightness have increased significantly. Naturally, the quality of LCD projectors far exceeds that of CRT-type three-gun projectors, and thus has become the mainstream of large-size displays.

In simple terms, LCD projectors can be roughly decomposed into three parts: optical system, LCD module and electronics. The optical system is not only complex, but also involves a wide range of technical aspects and scopes, including optical specification measurement, optical system architecture, optical design, light source module, light splitting and combining components , projection lens and screen, etc. As for the LCD module, it is the device that controls the projector to display images. The main considerations are RGB pixel arrangement, liquid crystal characteristics, etc., including the common silicon crystal TFT (thin film transistor) process technology, which has a direct impact on image resolution. The last electronic part processes the input electronic image signal and then transmits the color electronic signal to be displayed to the LCD module.

The basic principle of LCD projection is to use LCD modules to modulate the color of light emitted by the light source and projected onto the screen. In order to accurately project the color of the image, the color of the light source needs to be separated into three colors: R, G, and B, and then combined into one and projected onto the screen using a projection lens. LCD projectors are divided into two types: Video type that cannot be connected to a computer and Data type that can be connected to a computer, depending on the different electronic signals they receive. They can be divided into front projection type (Front Projector) and rear projection type (integrated with the screen) (Rear Projector) according to the different positions of the viewer and the screen. They can also be divided into single-chip type and three-chip type due to the different number of LCD panels used.

With a general understanding and knowledge of projectors, you will not be helpless when problems and failures occur. So, what are the common problems in the use of LCD projectors?

Common problems and solutions

The LCD projector's power switch is already in the "ON" position, but why doesn't the bulb light up?

This reason can be divided into the following situations:

Most LCD projectors have a stand-by function to solve the heat dissipation problem. When the power switch is turned to the "ON" position, please check whether the stand-by function is canceled. The bulb may be broken, so you must replace it or switch to a spare bulb before you can continue to use it. Another possibility is that the power switch itself is faulty, or there is a problem with the circuit that controls the light source, so it must be sent back to the manufacturer for processing.

Why does the image projected by an LCD projector have a trapezoidal phenomenon of "big head and small tail" or "narrow on the left (right) and wide on the right (left)"?

When the trapezoidal phenomenon of "big head and small tail" occurs, some LCD projectors are equipped with a keystone correction adjustment button (up to 18 degrees on the market) to improve this situation. The situation of "narrow on the left (right) and wide on the right (left)" is because the LCD projector is not placed parallel to the screen. Or you can raise the projector to make it 90 degrees with the screen.

Why does noise or blurred text occur when an LCD projector is connected to some computers ?

Generally speaking, LCD projectors are more compatible when connected to computers, but when connected to laptops, compatibility issues may arise because the bandwidth of the signals (VGA or SVGA) output by each laptop is not uniform. However, you can adjust the Frequency, Contrast and Tracking buttons on the "single gun" to achieve the perfect picture you need.

Why is the image projected by an LCD projector bright in the center and dark around it?

In fact, all images projected by LCD projectors will have such phenomenon. This is a design problem of the machine itself and cannot be overcome. The only way is to make more comparisons before purchasing.

Why is the LCD projector not as bright as before after using it for a period of time?

Nowadays, most LCD projectors use built-in bulbs to project images, and the life of the bulbs can be divided into metal bulbs, about 1,000 hours, and halogen bulbs, about 100 to 200 hours. Metal bulbs have a longer life, but their brightness decreases linearly with the use time. After about 120 hours of use, the brightness is only 70% of the original. Although the life of halogen bulbs is short, the brightness is consistent during use. It is bright when it is bright and not bright when it is not bright.

Why can't LCD projectors have two sets of lamps, main and backup, like traditional overhead projectors? What if the lamp burns out during an important meeting?

In fact, not all LCD projectors are without main and backup bulbs. All LCD projectors that use metal bulbs have only one bulb, so you must always have a backup bulb ready. Another point is that some brands of projectors may need to be replaced by the original salesperson because it is not easy to replace. However, LCD projectors that use halogen bulbs on the market have two sets of main and backup bulbs for replacement in case of temporary situations. Even if both sets of bulbs are burned out, they can be replaced without any tools. So you should pay attention to this when you buy a computer LCD projector.
Why are the bulbs of LCD projectors on the market so expensive?

This is because the metal bulb projectors have special specifications and cannot be shared with other brands, so they cannot be mass-produced. In contrast, halogen bulbs use universal specifications and are therefore cheaper.

Why are the sounds of the built-in speakers in LCD projectors not very loud?

Because the main effect of LCD projectors is its perfect picture, the sound is generally not very loud. If the sound is loud, the loudspeaker must be of a certain size, which will take up a lot of machine space. But now the LCD projectors on the market also have sound output terminals, which can be used with the audio equipment of the conference room itself. If there is better audio equipment, you can even adjust the bass, treble, left and right channel balance and simulate 3D effects.

Maintenance during use is the key

The use of LCD projectors is a process of exerting their functions and services. However, if misoperation or improper use occurs, it is also a critical period that can easily cause the projector to malfunction and reduce its service life. Therefore, maintenance during use is very important. When using, pay attention to the quality of the power supply and prevent overload; pay attention to shock protection, and it is strictly forbidden to move the instrument during use.

In addition, special attention should be paid to the maintenance and care of the bulb during use. The bulb is a key component of the projector. Most of the more advanced LCD projectors now use UHP bulbs. Compared with the commonly used metal halide lamps, this bulb has the advantages of higher brightness, higher electro-optical conversion efficiency, and longer life. The basic life of the bulb is more than 4000 hours. After 2000 hours of use, it enters a decay state, but the brightness can still reach 80% of the original. It is a very ideal cold light source . When the power is on, the filament is in a high temperature state. At this time, it is strictly forbidden to vibrate or move the projector to prevent the bulb from bursting. The bulb is expensive, most of which are more than thousands of yuan. In order to extend the service life of the bulb, avoid frequent switching of the power supply during use , and do not use it continuously for too long.