For the monitor provided for testing
Each person develops inexplicable preferences over time, based on a number of factors. For example, if several of your friends have had no problems with a Samsung microwave oven, then most likely you will be predisposed to buying a Samsung microwave oven. And vice versa - it’s worth telling one of your friends how his processor of the company "X" burned out, and you will be wary of any failures of the processors of this company for a long time, even if, according to statistics, they practically do not burn, just a friend - the famous "crooked hand" ". If you have decided to purchase an LCD monitor for the first time, then most likely you do not yet have preferences and superstitions. What about domestic products? Can we immediately say that Russian monitors are worse than imported ones? Of course not. But what is usually hidden under the term "domestic monitors"? As you know, LCD matrices, LCD monitor housings and most of the other components for them are not produced in Russia. The maximum you can count on is a domestic "screwdriver" assembly, but most firms simply place orders in Taiwan or China, from where ready-made models come, even equipped with branded stickers and logos. There is nothing to be ashamed of - there are far more brands in the world than actual product manufacturers, and even the leading and largest firms order their monitors (laptops, boards, etc.) from other major manufacturers.
| Main characteristics | |
| Model | Bliss 1700RT (Nexus brand) |
| OEM manufacturer | TVT |
| Horizontal Bandwidth | 24-80 kHz |
| Vertical bandwidth | 50-75 Hz |
| Total Bandwidth | 140 MHz |
| Rated resolution | 1280x1024 |
| Recommended sweep frequency | 60 Hz |
| Plug & Play ID | TVT002D |
| Serial number | 1091 (13401091) |
| date of manufacture | 2003, fourth week |
| EDID version | 1.3 |
| Interfaces | DVI, D-Sub, Audio (stereo 2x1W) |
| portrait mode | Supports |
| Screen Rotation Software for Windows | Not |
| Response time | 25ms (15/10) |
| Price | $545 (manufacturer recommended) |
Today we are testing the Bliss 1700RT. The model is especially interesting because, unlike many "budget" models presented on the domestic market, it uses an LCD matrix with MVA technology. Today, these monitors are considered among the best, provide a larger viewing angle, better color reproduction and good response time, but at the same time, they are significantly more expensive than LCD counterparts with TN + Film, and are not so common. Let's start, as usual, with clothes.
The monitor literally shocked us with the size of the package - it would fit a decent-sized system unit without any problems, and not just a compact LCD panel. Inside, we found two massive foam dampers, a set of wires (DVI, D-SUB, a stereo cord for connecting built-in speakers and a power supply cable), as well as a power supply unit and unified documentation in Russian for the entire Bliss 17xx family. There were no CDs, drivers or utility utilities included.
The appearance of the Bliss 1700RT cannot be called particularly refined: classic contours, slightly smoothed lines, the most ordinary control buttons and a stand that is somewhat reminiscent of the cabin of a submarine - that, in fact, is all that can be said about this monitor. There are no design frills in the form of polished metal, openwork grilles and airy structures of the stand, even the speakers are hidden behind, so carefully that not everyone will guess that they exist at all.
The hero of today's article has a resolution of 1280x1024, a response time of 25 ms (15 ms - ignition, 10 ms - attenuation) and costs $545 in Moscow retail. In total, the Bliss LCD monitor range includes six varieties with a diagonal of about 17", of which two have a diagonal of 17.4 inches, and the remaining four are exactly 17". The 1700 series consists of three models: 1700, 1700RT and 1700DV. The hero of the occasion does not have S-Video and composite input, like 1700DV, but, unlike the simple 1700, it is equipped with a DVI port. As a result, its price is set exactly in the middle between $495 for the 1700 model and $695 for the 1700DV model, despite the fact that the 1700DV has worse viewing angles and lower contrast. The Bliss 1700RT matrix, thanks to the use of MVA technology, has an excellent viewing angle - 170 degrees vertically and the same horizontally. Other characteristics:
| Screen | TFT LCD (Chi Mei Optoelectronics, MVA technology) |
| Video inputs | Analog. RGB, digital DVI |
| Colors | 16.7 million |
| Permission | 1280x1024 (up to 75Hz, manufacturer recommends 60Hz) |
| Sound | 2x1w, stereo, built-in. din. |
| Response time | 15/10ms (25ms total) |
| Weight | 8.6 kg |
| Contrast | 500:1 |
| Nutrition | 90-264V 55W (5W standby) |
| Brightness | 250 cd/m |
| Viewing angle | Vertical - 170 degrees Horizontal - 170 degrees |
Let's highlight the fact that the panel weighs 8.6 kg, that is, it is relatively heavy (for comparison, the Acer AL712 tested not so long ago weighs 7.3 kg together with the stand). The reason is simple - the Bliss monitor is equipped with an impressive base, necessary for the screen to work steadily in portrait mode.
The main feature of the monitor is the LCD matrix manufactured by Chi Mei Optoelectronics, which uses MVA technology. Today, three main technologies are popular with manufacturers: TN + Film, IPS and MVA. The first one is the easiest to manufacture, but due to a number of technical features it provides a smaller viewing angle and therefore has a special polarized coating on the screen, which increases the viewing angle. Recognizing a TN+Film monitor is easy: looking at the image from above, you will see how it becomes lighter, and looking at the bottom, you will see that it darkens noticeably. In recent years, TN + Film technology has stepped far forward, modern monitors have a good response time (up to 16 ms) and quite decent viewing angles. What's more, despite claiming lower contrast ratios, the best TN+Film monitors can actually deliver higher contrast ratios than some MVA monitors. For example, last year we tested 14 15" LCD monitors, including the Neovo F-15 and ViewSonic VX500. The former only lists 260,000 colors. The latter has 16 million. The F-15 has a 300:1 contrast ratio. , while the rival has 400: 1. However, despite the specifications, the TN + Film monitor was able to display more shades.
Note: 15" matrices mostly use 6 bits per color (including MVA). But most often you will see numbers of 16.7 million colors. Rarely does anyone honestly write 262K, since monitors dither up to 16 million. On On the Viewsonic website, the VX500 has angles of 135 and 125, while the authors of the MVA technology assure us of 160 and 160. So is it using MVA technology or not? and response time are very dependent on the correct operation of the monitor controller.The Bliss 1700RT has an M 170E4 matrix (MVA): 16.7 million colors, a response time of 15/10 and 8 bits per color, but, as test results show, no everything is so perfect.
It is also known that one of the problems of TN + Film is color reproduction, as well as insufficient blackness, which is associated with the inability to deploy liquid crystals perpendicular to the backlight. And these problems are being solved, but many experts still consider MVA to be a promising technology. It would be appropriate to note that all expensive and prestigious monitors are mostly made using MVA technology. It allows you to combine large viewing angles, low response time and good black color, which is not observed in other technologies.
MVA (Multi-Domain Vertical Alignment) technology was developed by Fujitsu, first introducing monitors using Vertical Alignment technology to the market in 1996. VA had the most important disadvantage:
When looking at the monitor from the side, the color shades were noticeably distorted, that is, the viewing angle was significantly reduced even at small deviations from the center. At the same time, if, for example, you displayed an image saturated with blue, then on the one hand the VA monitor showed it with noticeably purer shades of blue, and on the other hand it became completely black, as the view passed through half-turned crystals (see illustration).
A year after the appearance of VA, Fujitsu laboratories managed to achieve the desired result - they managed to solve the problem with incorrect color reproduction of the panel, and the first generation of monitors with MVA technology was born. In it, the subpixel was divided into several zones, the polarizing filters became noticeably more complex - they added a domain structure formed by the protrusion method. To expand the viewing angle, the color elements are divided into zones and cells formed in the domain structure of the filters from the inside, and due to this they can move independently of neighboring LCD crystals in opposite directions. With such an organization, the viewer, regardless of the viewing angle, sees the same shade of color. Here's what it looks like in practice:
The first truly successful MVA monitors began to appear in 2001, and today several large manufacturers make matrices using MVA technology. Unlike TN+Film, MVA monitors have another important plus - dead pixels on them do not look like bright color or white dots, but black, due to the fact that the switched off LCD crystal unfolds as shown in the figure above, becoming opaque black. When you test your first MVA monitor in a showroom before buying, keep this in mind. Dead pixels can only be seen if the screen is filled with a uniform white color (similarly for IPS technology).
From the jungle of technological features of MVA, let's return to our specific monitor. The characteristics of the Bliss 1700RT are impressive - a contrast ratio of 500:1 (!) can be considered an excellent indicator, and a brightness of 250 cd / m2, although not a record, is also good. The stock is large enough, which will come in handy on a bright sunny day, when a beam from a window can fall on the screen. During our testing in this light, most CRT monitors became unusable, but the Bliss 1700RT did well, and that it was brightly lit was only noticeable by the now dazzling white plastic edging.
Color rendition caused not so unambiguous emotions. The manufacturer claims that the screen is capable of displaying 16.7 million shades of color. We would not be so optimistic. In the course of several hours spent calibrating the monitor, we came to a disappointing conclusion - we can talk about a maximum of 18-bit color. First, how the monitor displays color when connected via D-Sub. Gradient tables are reproduced with obvious flaws, the transitions between the border shades of blue, red and green are full of inaccuracies and sharp jumps. Between the dark and medium shades of all colors, the transition can be called sudden. The monitor likes to reproduce shades of blue as shades of cyan, and even the black-and-white gradient is not fully reproduced. When switching the color temperature, the gray gradient noticeably goes into blue or yellow. There is a general tendency to lighten the image. If you plan to work with graphics, then we do not recommend paying attention to 1700RT.
On the other hand, the monitor is quite suitable for everyday needs - the colors are juicy, bright shades of yellow, green, and red are reproduced especially well. We were literally captivated by the black color of this display - it looked even blacker than on the "seed" with a CRT installed next to it for comparison.
It should be noted that the monitor reproduces light colors quite well. So, the background of the Tom's Hardware website, which looks bright white on some LCD monitors, is actually light beige, and Bliss 1700RT demonstrated this with default settings.
When connected via DVI, the following picture was observed: the color gradients became smoother, but the aliasing was still preserved. As with RGB, there were curious artifacts - imagine a fill from dark blue (RGB 0:0:1) to light blue (RGB 0:0:255). Looking at the gradient, you see not a smooth transition of shades, but a ladder, while the first step is dark, the second is lighter, the third is darker (!), the fourth is lighter than the second, the fifth is even lighter, and the sixth is a little darker than the fifth. It is difficult to explain in words, but it looked exactly like that. You can get the gradients image from the following links: blue gradient , green gradient And red gradient .
Let's move on from static gradients to dynamics.
A response time of 25ms allows you to play active games, but this is clearly not enough for the most dynamic scenes. We usually test monitors on modern 3D games, including Need For Speed: Hot Pursuit 2 and Unreal Tournament 2003. In the case of Bliss 1700RT, we also added good old Quake to the test basket, which shows huge FPS at any resolution (over a hundred frames per second at 1600x1200). The test showed that the image is smeared with sharp jerks, and fast moving objects leave a clear static trail. However, the afterglow effect of the Bliss 1700RT is not as pronounced as we expected. There is no difference between low resolutions (320x240-1024x768) in dynamics - the monitor's decoder copes well with image scaling, but the overall slowness of the matrix affects - this monitor is not ideal for an advanced player, although it allows you to run dynamic games.
In any case, if you are a fan of the action genre and ultra-high FPS, then you should pay attention to more expensive models with a response time of 20 or even 16 ms. By the way, when choosing a monitor, keep in mind that sometimes manufacturers indicate only one number - the ignition or decay time of a pixel. If the figure is less than 16 ms, then this is exactly it, because today there are no monitors with a total response time of less than 16 ms. Returning to the Bliss 1700RT, we note that the monitor works well in tandem with an external TV tuner - the turn-on time after signal loss is short, and it does not bother you when switching channels. This monitor is also perfect for watching DVDs - the settings allow you to achieve very rich and bright colors, albeit to the detriment of some accuracy in the reproduction of shades.
By the way, paired with a TV tuner, built-in speakers will also come in handy. As usual, they didn't impress us. "Flat" sound without pronounced mids and lows is not capable of anything other than sounding Windows, playing quiet music in the background and ... perhaps for sounding TV channels. Of course, there will be no desire to watch movies on such acoustics, but you are always welcome to listen to the news or the weather forecast. And it saves space on the desktop.
Modern video cards and laptop graphics chips are able to independently rotate the image so that you can use the LCD panel in portrait mode. Now you don't need third-party software (like Pivot, for example), which means you can forgive the Bliss 1700RT for not including any CD with drivers and software.
We tested the monitor in portrait mode on an nVidia graphics accelerator with the Detonator 43.25 driver installed, which has built-in image rotation functions. In general, there were no particular drawbacks - it is convenient to turn the screen around, for this it is enough to slightly tilt it away from you, and then, holding the sidewall with both hands, carry out the required operation. But there is one significant disadvantage - the monitor menu does not expand, this option is not provided by the manufacturer. If you decide to change any panel settings, you will either have to twist your neck or turn the screen back.
The Bliss 1700RT let down the buttons - they are very tight and, by pressing them, you will surely shake the screen a lot. The button to turn on the display is not intuitive - to switch to the active mode, you need to hold it for a few seconds, which does not occur to everyone. So, out of 5 people whom we asked to turn on the monitor, four of them briefly pressed the power button, they were very surprised at the lack of response from the panel.
Wires are connected conveniently - for greater comfort, you can turn the screen into portrait mode, and then access to all the main connectors will open. In the photo you can see DVI and D-Sub connectors, a mini-jack connector for built-in speakers and a hole for connecting a power supply unit, which, by the way, is external, which made it possible to slightly reduce the weight of the panel.
The monitor power button has another function: a short press of it when the monitor is on brings up a menu with which the panel is configured.
Here you will find a gentleman's set of functions - from color temperature settings to adjusting the position of the menu on the screen. Note that the 1700RT does not support the Russian language, and this is sad if you remember that Bliss is a national trademark. The menu is grouped ingenuously - all the main sections are placed in one line, and by selecting the one you need and pressing "+" or "-", you get to the submenu with settings. When connected via D-Sub, phase and frequency settings appear. What we didn't like yet was the interface selection point (D-Sub/DVI) hidden far away, which is inconvenient if you decide to connect an external TV tuner or a second computer (for example, a laptop) to the monitor. An interesting feature of the auto-tuning system: if you are watching a widescreen movie in Windows Media Player, then by pressing the adjustment button, the monitor is optimized so that the video is pressed close to the top edge of the screen. Is it a gift to the user or a lack of monitor firmware, we could not decide for ourselves.
Text scaling from lower resolutions was a little disappointing. The monitor supports several modes, but they all look a little smeared. The best (so-called bicubic) is installed by default, and in general, the monitor is well configured right from the factory.
Graphics scaling, on the contrary, was pleasant. Movies, when viewed at lower resolutions, look good, and dynamic games run decently on the Bliss 1700RT, especially with anti-aliasing. You may not even think that you are looking at a scaled image. The situation is similar with photographs. During the tests, we ourselves did not believe that the photos on the screen were not viewed in the nominal mode for the monitor.
We liked the Bliss 1700RT. Thanks to the use of MVA technology, it has excellent viewing angles, excellent contrast and a sufficient margin of brightness. The color rendition let us down - the transitions between shades are not soft enough, the display clearly does not pull out the declared 16.7 million shades. This is not to say that it is cheap - you can buy a 17-inch LCD screen that uses an inexpensive TN + Film matrix for $ 100 cheaper, but we thought the price difference was quite justified. The response time is not bad by today's standards, but it is not enough for fast-paced games.
There were no downsides. First of all, we note the unimpressive design of the monitor. It would have been good three years ago, but against the background of modern delights of market leaders, it looks gray. The buttons were let down - very tight and uninformative. The menu is not as pretty and does not have some functions, but it does its job well. The last disadvantage is the heavy weight of the monitor, but due to the heavy stand, it works without problems in portrait mode, and you don’t have to worry about its stability.
Pros:
- Large diagonal (comparable to 18-19" CRT)
- Smartly implemented autotuning
- Juicy colors (good to watch DVD)
- Good rendering of light colors
- Scales well at lower resolutions, especially graphics
- Works in portrait mode
Minuses:
- Does not show the claimed 16.7 million shades of color
- Switching D-Sub / DVI got lost somewhere in the wilds of the menu
- Response time is not enough for the most dynamic games
- a bit heavy
Most modern LCD monitors have a fairly simple construction, if we consider it at the chip level, i.e. in the monitor we now see two or three large microcircuits. The functional purpose of these microcircuits in most cases is typical, despite the fact that they are produced by different manufacturers and have different markings. And since the microcircuits perform the same functions, their input / output signals will be almost identical, i.e. the main difference between microcircuits lies in their characteristics and the pinout of the case. That is why most modern LCD monitors, regardless of their many brands and many different models, can be applied to the same approaches for troubleshooting and repair. Apart from the identical functional diagram, almost all LCD monitors share the same layout, i.e. almost all manufacturers have come to the same scheme for distributing the electronic components of the monitor on various printed circuit boards.
General scheme of a modern monitor
A modern LCD monitor, as a rule, consists of the LCD panel itself and 3 printed circuit boards (diagram 1):
Scheme 1 - General scheme of a modern monitor
- main control and signal processing board (Main PCB)
- power supply board and backlight inverter (Power PCB)
- front panel board
Connections with this arrangement of the monitor are shown in diagram 2.
Scheme 2 - Interblock connections
Many modern monitors can be used as a USB hub to which various USB devices can be connected. Therefore, another printed circuit board corresponding to the USB hub may appear in the monitor, but the presence of this board, of course, is optional.
The main control board houses the monitor microprocessor and the scaler. This board processes monitor input signals and converts them into LCD panel control signals. This board largely determines the quality of the image reproduced on the monitor screen. The main difference between monitor models from each other lies in the configuration of this printed circuit board, in the type of microcircuits installed on it and in their “firmware”.
The front control board is a narrow printed circuit board with only buttons and an LED.
Monitor power board
The power supply board (in the LG documentation it is referred to as LIPS), is a combined power supply that consists of two switching converters: the main power supply and the backlight inverter. This board generates all the main voltages necessary for the operation of both the main board and the LCD panel, and also generates a high-voltage voltage for the backlight lamps. It is this printed circuit board that gives the most various problems and failures of LCD monitors.
But there is a second layout option, in which, in addition to the LCD matrix, the monitor has four printed circuit boards:
- main control and signal processing board (Main PCB)
- power supply board (Power PCB)
- backlight inverter board (Back Light Inverter PCB)
- front panel board
In this layout, the power supply and backlight inverter are separate printed circuit boards (diagram 3).
Diagram 3 - Main monitor boards
Interconnections typical for such a monitor layout are shown in Figure 4. As an example, LG FLATRON L1810B and L1811B monitors can be presented here.
Scheme 4 - Interblock connections
Before talking about the various options for the circuitry of LCD displays, let's give a brief description of the main components that they consist of.
Microprocessor
The microprocessor, which in various sources can be referred to as CPU, MCU and MICOM, is responsible for the overall control of the monitor. Its main functions are:
- generating signals to turn on and off the backlight
- backlight brightness control
- scaler operation mode setting
- generation of signals controlling the operation of the scaler
- processing and control of input clock signals HSYNC and VSYNC
- determining the monitor's operating mode
- determining the type of input interface (D-SUB or DVI)
- front panel signal processing
The control program of the microprocessor, as a rule, is located in its internal ROM, i.e. this program is "written" in the microprocessor. However, part of the control code, and especially various data and variables, is stored in an external non-volatile memory, which is an electrically reprogrammable ROM - EEPROM. The microprocessor has direct access to the EEPROM chips.
The microprocessor, as a rule, is 8-bit and operates at clock frequencies of the order of 12 - 24 MHz. The microprocessor, in fact, is a single-chip microcontroller, which, in addition to the CPU, also contains:
- multi-purpose digital I/O ports with programmable features
- analog input ports and digital-to-analog converter
- clock generator
- RAM and other elements
EEPROM
Non-volatile memory primarily stores monitor settings and user-defined settings. This data is retrieved from the EEPROM when the monitor is turned on and the microprocessor is initialized. Each time you adjust the monitor and set a new custom value for any image parameter, these new values are overwritten in the EEPROM, allowing them to be saved. In modern monitors, chips with serial access over the bus are mainly used as EEPROM. I2C(signals SDA And SCL). These are chips of the type 24C02, 24C04, 24C08 etc.
DDC-EEPROM
All modern monitors support Plug & Play technology, which involves the transfer of passport and configuration information about the monitor from the monitor to the PC. To transfer this data, a serial DDC interface is used, to which the signals on the interface correspond DDC-DATA (DDC-SDA) And DDC-CLK (DDC-SCL). The passport information itself is stored in another EEPROM, which is practically directly connected to the interface connector. The same microcircuits are used as EEPROM 24C02, 24C04, 24C08, and a more specialized one can also be used - 24C21.
RESET shaper
The RESET signal generation circuit provides control of the microprocessor supply voltage. If this voltage falls below the allowable value, the microprocessor is blocked by setting the REST signal to a low level. As a signal conditioner, a stabilizer Low Drop chip, such as KIA7042 or KIA7045, is most often used.
The scaler microcircuit processes the signals coming from the PC. The scaler in most cases is a multifunctional microcircuit, which usually includes:
- microprocessor;
- receiver (receiver) TMDS, which provides reception and conversion to a parallel form of data transmitted via the DVI interface;
- analog-to-digital converter - ADC (ADC), which converts the input analog signals R / G / B;
- PLL block, which is necessary for correct analog-to-digital conversion and synchronous generation of signals at the output of the ADC;
- a scaling circuit (Scaler) that converts an image with an input resolution (for example, 1024x768) into an image with an LCD panel resolution (for example, 1280x1024);
- OSD driver;
- a transmitter (LVDS) that converts parallel color data into a serial code transmitted to the LCD panel via the LVDS bus.
In addition to these basic elements, some scalers also include a gamma correction scheme, an interface for working with dynamic memory, a frame grabber scheme, format conversion schemes (for example, YUV to RGB), etc.
In fact, the scaler is a microprocessor optimized for performing quite specific tasks - image processing. The scaler adjusts to the format of the input signals by receiving the appropriate commands from the monitor's CPU.
If the monitor has a frame buffer (RAM), then working with it is a function of the scaler. To do this, many scalers are equipped with an interface for working with dynamic memory.
An example of a functional diagram of the GM5020 scaler used in the LG FLATRON L1811B monitor is shown in Figure 5. The feature of this scaler is that it does not contain an internal LVDS transmitter and generates color signals in the form of a parallel 48-bit digital data stream. When using the GM5020 scaler, an external LVDS transmitter is also required, which is a specialized microcircuit.
Diagram 5 - Scaler Diagram
framebuffer
A framebuffer is a large enough capacity RAM that is used to store an image of an image displayed on the screen. This memory is required when converting (scaling) the image, i.e. when the input resolution does not match the resolution of the LCD panel. The frame buffer is a dynamic type of memory, most often SDRAM. The capacity of this memory is determined by the developer based on the format of the LCD panel and its color characteristics.
DC-DC Converter
This module provides the formation of all constant voltages necessary for the operation of the monitor. These voltages are: +5V, +3.3V, +2.5V or +1.8V. The converters are either linear or pulsed DC voltage converters.
Clock Buffer
Sync buffers are amplifiers made either on transistors or on small logic microcircuits. The buffer provides amplification and buffering for the HSYNC and VSYNC clock inputs. Often the buffers are controlled by the microprocessor, which allows you to select the signal source, as well as select the type of synchronization (separate, composite or SOG).
inverter
The inverter generates high voltage and high frequency voltage for backlight lamps. It is a pulse high-frequency converter, which creates a pulse voltage with an amplitude of about 800V from + 12V voltage.
Power Supply
The power supply unit generates +12V and +5V DC voltages from the mains AC voltage, which are used to power all monitor cascades. The power supply is switching and can be either an external network adapter or an internal monitor module, although the monitors presented in this review have an internal power supply.
The vast majority of LCD monitors can be attributed to one of the 3 basic circuitry options, which we will try to characterize.
1) The first option - microprocessor and scaler microcircuits
characterized by the presence of two main microcircuits on the MAIN BOARD: a microprocessor microcircuit and a scaler microcircuit. The microprocessor performs the overall control of the monitor components, and the scaler performs the conversion of color signals, i.e. adjusts the image to the resolution of the LCD panel. In this case, the scaler processes data on the fly, i.e. without first saving the image image in the intermediate memory. Therefore, memory chips are not used in this version of circuitry. A block diagram of such an LCD monitor is shown in Figure 6.
Scheme 6 - Microprocessor and scaler microcircuits
2) The second option -
differs from the first in the presence of memory chips in the monitor, which are often called the frame buffer (Frame Buffer). The presence of memory chips is typical for monitors of a higher class, which are able to work with images of various input formats, including television ones. This class of monitors mostly includes 18-inch monitors, such as FLATRON L1811B.
Scheme 7 - Microprocessor, scaler and memory microcircuits
3) The third option - Active chip
It is characterized by the presence of only one "active" microcircuit on the main board MAIN BOARD. By the term "active microcircuit" we mean a microcircuit that has its own command system, is programmable to perform various functions and is capable of performing some kind of signal processing. In some monitors (for example, in FLATRON L1730B and L1710S), we see only one such microcircuit, which combines both the functions of a microprocessor and the functions of a scaler. Since such microcircuits can be used in various models of monitors, and since the microprocessor contains a microprocessor, which requires control codes, we will also find a read-only memory chip on the MAIN BOARD board - ROM (ROM). This chip, which is most commonly an 8-bit parallel access ROM, contains the control program for operating the scaler-microprocessor combo chip. Often the ROM chip is electrically reprogrammable and is therefore often referred to as FLASH. Almost all LG monitors use the AT49HF family chip as a ROM. A block diagram of monitors with such circuitry is shown in Figure 8.
Scheme 8 - Active chip
Additional option - Scaler without built-in LVDS transmitter
In addition to these three options for constructing a monitor, one more option can be introduced. It differs in that the monitor uses a scaler that does not have a built-in LVDS transmitter. In this case, the transmitter corresponds to a separate microcircuit, which is installed on the main board between the scaler and the LCD panel. The LVDS transmitter converts the parallel (24 or 48 bit) digital data stream generated by the scaler into serial data on the LVDS bus. The LVDS transmitter is a general purpose IC that can be used in any monitor. Such circuitry, with an external LVDS transmitter, is also typical, to a greater extent, for higher-end monitors, because. they use specialized scalers with fewer additional features. An example of a block diagram of a monitor with a similar circuitry is shown in Figure 9. As an example of a monitor with such a construction, we can name the model LG FLATRON L1811B.
Scheme 9 - Scaler without built-in LVDS transmitter
Here, only the basic options for modern circuitry were considered, although in all the variety of models and brands of LCD monitors, you can find a variety of combinations of the block diagrams presented. The summary table 1 reflects the types of microcircuits used and the features of the circuitry of the most popular models of LG monitors.
Table 1 - Features of LG TFT monitor circuitry
|
Monitor model |
Layout option |
Circuit variant |
Types of main microcircuits |
Type of used LCDpanels |
||
|
CPU |
Scaler |
LVDS |
||||
|
L1510S |
see fig.1 |
see fig.6 |
MTV312 |
MST9011 |
LM150X06-A3M1 |
|
|
L1510P |
see fig.1 |
see fig.6 |
MTV312 |
MST9051 |
LM150X06-A3M1 |
|
|
L1511S |
see fig.1 |
see fig.9 |
MTV312 |
GMZAN2 |
THC63LVDM83R |
1) LM150X06-A3M1 2) LM150X07-B4 |
|
L1520B |
see fig.1 |
see fig.6 |
MTV312 |
MST9011 |
LM150X06-A4C3 |
|
|
L1710S |
see fig.1 |
see fig.8 |
GM2121 |
1) HT17E12-100 2) M170EN05 |
||
|
L1710B |
see fig.1 |
see fig.6 |
MTV312 |
MST9151 |
1) LM170E01-A4 2) HT17E12-100 3) M170EN05V1 |
|
|
L1715 /16 S |
see fig.1 |
see fig.6 |
MTV312 |
MST9111 |
LM170E01-A4 |
|
|
L1720B |
see fig.1 |
see fig.6 |
MTV312 |
MST9111 |
1) LM170E01-A4 2) LM170E01-A5K6 3) LM170E01-A4K4 4) LM170E01-A5 |
|
|
L1730B |
see fig.1 |
see fig.8 |
GM5221 |
1) LM170E01-A5K6 2) LM170E01-A5N5 3) LM170E01-A5KM |
||
|
L1810B |
see fig.3 |
see fig.6 |
MTV312 |
MST9151 |
1) LM181E06-A4M1 2) LM181E06-A4C3 |
|
|
L1811B |
see fig.3 |
see fig.9 |
68HC08 |
GM5020 |
THC63LVD823 |
1) LM181E05-C4M1 2) LM181E05-C3M1 |
|
L1910PL |
see fig.1 |
see fig.6 |
MTV312 |
MST9151 |
FLC48SXC8V-10 |
|
|
L1910PM |
see fig.1 |
see fig.6 |
MTV312 |
MST9151 |
FLC48SXC8V-10 |
|
conclusions
An analytical review of the data presented in Table 1 leads to several interesting conclusions.
Firstly, almost all monitors presented in Table 1 have the same layout scheme, which, by the way, is typical for almost all modern monitors, regardless of the manufacturer.
Secondly, LG in its monitors mainly uses a microcontroller as a control processor MTV312 developed by the company MYSON TECHNOLOGY. This microcontroller is based on the famous microprocessor 8051. In addition, the microcontroller includes RAM, Flash ROM, ADC, synchronization processor, digital ports and a number of other elements.
Thirdly, It should be noted that some monitor models may use different types of LCD panels. So, for example, under the cover of monitors sold under the brand name FLATRON 1710B, you can find LCD panels of three different types: LM170E01-A4, HT17E12-100, M170EN05V1, and this is a very common practice of almost all monitor manufacturers. But interesting is the fact that sometimes LG uses panels from other manufacturers in its monitors, while being the world's largest manufacturer. The belonging of the LCD panel can be determined by its marking, the first letters of which determine the manufacturer:
- LM– production panels LG-PHILIPS
- HT– production panels HITACHI
- M– production panels AUO
- FLC– production panels FUJITSU
Advantages
The AcerView FP855 performed well in tests for the ability to set the desired level of brightness and contrast, and demonstrated smooth color transitions.
Supported technology "intelligent" auto-scaling of the image. The Acer FP855 has a scaling technology that not only stretches the image to fill the screen, but also makes it as realistic as possible by automatically adding new color shades. The iKey function allows you to automatically adjust the image parameters for a specific video mode with a single keystroke: with a single press of a button, you can adjust the color temperature, horizontal and vertical position of the image, image focus (frequency and phase adjustment). The setup takes about a second, while the monitor shows which setting is currently being adjusted. The new iWheel on-screen menu system and the control functions that allow you to adjust the monitor in manual mode have become much more convenient than the FP751 model. By turning the special wheel up or down, the user can adjust the brightness and contrast of the image, bypassing the on-screen menu. At the same time, corresponding pictures appear on the screen, by which you can control the process. To enter the on-screen menu, you need to press the wheel and rotate up / down to move through the menu items, selecting them or setting any parameter by pressing. on the right side), as well as a USB hub. The kit includes a CD-ROM with drivers and a demo program. The monitor has a simple but ergonomic design (especially note the recess for various small things in the stand) and complies with the TCO'99 standard. Also, as an advantage, it should be noted the presence of a user manual in Russian.
disadvantages
The wheel for selecting and setting modes is too “nimble”: instead of pressing, it often turns and, therefore, moves to another menu item. The media speakers are too close together. The power supply is built directly into the stand, so the power cord goes from the monitor directly to the outlet, which, on the one hand, undoubtedly looks better from an aesthetic point of view and is more convenient to use, and on the other hand, it can cause distortion in the image during power surges , in the event of a power supply failure, the entire “base” will need to be repaired. And finally, it should be noted the low reaction speed for modern LCD monitors when objects move quickly across the screen and a rather high price.
Overall rating
AcerView FP855 is a high performance monitor. The picture during the tests was of very decent quality, which, moreover, practically did not deteriorate with an increase in the viewing angle.
The minimum price of the monitor in the Russian market is $3,050.
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Advantages The Bliss 1700 monitor showed good results in color reproduction, good contrast and smooth color transitions. The image quality does not degrade as the viewing angle changes. Two analog inputs (traditional 15-pin VGA D-Sub) are used to connect to personal computers. Supported technology "intelligent" auto-scaling of the image. The tuning subsystems, although not the best among the models that participated in our testing, are quite convenient. It should be noted as an advantage the presence of a detailed user manual in Russian and a low price for this class of devices. In addition, this monitor has the lowest price on our market among 17-inch models. disadvantages Too modest, somewhat "archaic" design (if, of course, this term can be used to describe such a technological innovation as an LCD monitor). However, this is perhaps the only drawback of Bliss monitors. Overall rating Bliss 1700 continues the tradition of the popular Bliss series of monitors and, not inferior in quality to more expensive models from other manufacturers, has a very attractive price. The image on this monitor is of very high quality, which also does not degrade when changing the viewing angle. The minimum price of the monitor in the Russian market is $1525.
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In order to fix the LCD monitor with your own hands, you must first understand what main electronic components and blocks this device consists of and what each element of the electronic circuit is responsible for. Beginning radio mechanics at the beginning of their practice believe that success in the repair of any device lies in the presence of a circuit diagram of a particular device. But in fact, this is an erroneous opinion and a circuit diagram is not always needed.
So, let's open the cover of the first LCD monitor that came to hand and in practice we will understand its device.
LCD monitor. main functional blocks.
The LCD monitor consists of several functional blocks, namely:
LCD panel
The liquid crystal panel is a complete device. As a rule, the LCD panel is assembled by a specific manufacturer, who, in addition to the liquid crystal matrix itself, builds into the LCD panel fluorescent backlight lamps, frosted glass, polarizing color filters and an electronic decoder board that generates voltages from digital RGB signals to control the gates of thin-film transistors (TFT ).
Consider the composition of the LCD panel of a computer monitor ACER AL1716. The LCD panel is a complete functional device and, as a rule, it is not necessary to disassemble it during repairs, with the exception of replacing failed backlight lamps.
LCD panel marking: CHUNGHWA CLAA170EA
On the back side of the LCD panel there is a rather large printed circuit board, to which a multi-pin loop is connected from the main control board. The circuit board itself is hidden under a metal bar.
Acer AL1716 Computer Monitor LCD Panel
The printed circuit board has a multi-pin NT7168F-00010 chip. This chip is connected to the TFT matrix and is involved in the formation of the image on the display. A lot of conclusions depart from the NT7168F-00010 microcircuit, which are formed into ten loops under the designation S1-S10. These cables are quite thin and seem to be glued to the printed circuit board, on which the NT7168F chip is located.
The printed circuit board of the LCD panel and its elements
Control board
The control board is also called the main board ( Main board). The main board contains two microprocessors. One of them is an 8-bit SM5964 control microcontroller with an 8052 type core and 64 kB of programmable Flash memory.
The SM5964 microprocessor performs a fairly small number of functions. A keypad and a monitor operation indicator are connected to it. This processor controls the on / off of the monitor, the start of the backlight inverter. To save user settings, a memory chip is connected to the microcontroller via the I 2 C bus. Usually, these are eight-pin non-volatile memory chips of the series 24LCxx.
LCD main board
The second microprocessor on the control board is the so-called monitor scaler (LCD controller) TSU16AK. This microchip has many tasks. It performs most of the functions associated with converting and processing the analog video signal and preparing it for submission to the LCD panel.
With regard to the LCD monitor, you need to understand that this is inherently a digital device in which all control of the LCD pixels is done digitally. The signal coming from the video card of the computer is analog and for its correct display on the LCD matrix it is necessary to make a lot of transformations. This is what the graphics controller is designed for, and in another way the monitor scaler or LCD controller.
The tasks of the LCD controller include such as recalculation (scaling) of the image for various resolutions, the formation of the on-screen menu OSD, processing of analog RGB signals and sync pulses. In the controller, analog RGB signals are converted into digital ones by means of 3-channel 8-bit ADCs, which operate at a frequency of 80 MHz.
The TSU16AK monitor scaler communicates with the SM5964 control microcontroller via a digital bus. To operate the LCD panel, the graphics controller generates synchronization signals, clock frequency, and matrix initialization signals.
The TSU16AK microcontroller is connected via a cable to the NT7168F-00010 chip on the LCD panel board.
If the graphics controller malfunctions, the monitor usually has defects associated with the correct display of the picture on the display (stripes, etc. may appear on the screen). In some cases, the defect can be eliminated by soldering the scaler leads. This is especially true for monitors that work around the clock in harsh conditions.
During prolonged operation, heating occurs, which adversely affects the quality of soldering. This may cause malfunctions. Defects associated with soldering quality are not uncommon and are also found in other devices, such as DVD players. The cause of the malfunction is degradation or poor-quality soldering of multi-output planar microcircuits.
Power supply and backlight inverter
The most interesting in terms of study is the monitor power supply, since the purpose of the elements and circuitry are easier to understand. In addition, according to the statistics of power supply failures, especially switching ones, they occupy a leading position among all the others. Therefore, practical knowledge of the device, element base and power supply circuitry will certainly be useful in the practice of repairing radio equipment.
The LCD monitor power supply consists of two. The first one is AC/DC adapter or in another way network switching power supply (impulse). Second - DC/AC inverter . In fact, these are two converters. The AC/DC adapter is used to convert the 220 V AC voltage into a small DC voltage. Typically, voltages from 3.3 to 12 volts are formed at the output of a switching power supply.
A DC/AC inverter, on the other hand, converts a direct voltage (DC) into an alternating voltage (AC) of about 600 - 700 V and a frequency of about 50 kHz. An alternating voltage is applied to the electrodes of the fluorescent lamps built into the LCD panel.
Let's take a look at the AC/DC adapter first. Most switching power supplies are built on the basis of specialized controller chips (with the exception of cheap mobile chargers, for example).
In the documentation for the TOP245Y chip, you can find typical examples of power supply circuit diagrams. This can be used when repairing power supplies for LCD monitors, since the circuits largely correspond to the typical ones indicated in the description of the microcircuit.
Here are some examples of circuit diagrams of power supplies based on TOP242-249 series chips.
Fig 1. An example of a power supply circuit diagram
The following circuit uses dual Schottky barrier diodes (MBR20100). Similar diode assemblies (SRF5-04) are used in the Acer AL1716 monitor unit we are considering.
Fig 2. Schematic diagram of a power supply based on a chip from the TOP242-249 series
Note that the circuit diagrams shown are examples. Actual circuits of impulse blocks may differ slightly.
The TOP245Y microcircuit is a complete functional device, in the case of which there is a PWM controller and a powerful field transistor, which switches at a huge frequency from tens to hundreds of kilohertz. Hence the name - switching power supply.
LCD monitor power supply (AC/DC adapter)
The scheme of operation of a switching power supply is as follows:
Rectification of alternating mains voltage 220V.
This operation is performed by a diode bridge and a filter capacitor. After rectification on the capacitor, the voltage is slightly higher than the mains voltage. The photo shows a diode bridge, and next to it is a filter electrolytic capacitor(82 uF 450 V) - blue barrel.
Converting voltage and lowering it with a transformer.
Switching with a frequency of several tens - hundreds of kilohertz DC voltage (> 220 V) through the winding of a high-frequency pulse transformer. This operation is performed by the TOP245Y chip. The pulse transformer performs the same role as the transformer in conventional network adapters, with one exception. It works at higher frequencies, many times more than 50 hertz.
Therefore, for the manufacture of its windings, a smaller number of turns is required, and, consequently, copper. But you need a ferrite core, not transformer steel like 50 hertz transformers. Those who do not know what a transformer is and why it is used, first read the article about transformer.
As a result, the transformer is very compact. It is also worth noting that switching power supplies are very economical, they have high efficiency.
Rectification of the alternating voltage reduced by the transformer.
This function is performed by powerful rectifier diodes. In this case, diode assemblies marked SRF5-04 were used.
To rectify high-frequency currents, Schottky diodes and conventional power diodes with a p-n junction are used. Conventional low-frequency diodes for rectifying high-frequency currents are less preferred, but are used to rectify high voltages (20 - 50 volts). This must be taken into account when replacing defective diodes.
Schottky diodes have some features that you need to know. Firstly, these diodes have a low junction capacitance and are able to quickly switch - go from open to closed. This property is used to work at high frequencies. Schottky diodes have a low voltage drop of about 0.2-0.4 volts, versus 0.6-0.7 volts for conventional diodes. This property increases their efficiency.
Schottky barrier diodes also have undesirable properties that hinder their wider use in electronics. They are very sensitive to excess reverse voltage. When the reverse voltage is exceeded Schottky diode irreversibly fails.
A conventional diode, on the other hand, goes into a reversible breakdown mode and can recover after exceeding the permissible reverse voltage value. It is this circumstance that is the Achilles' heel, which causes the Schottky diodes to burn out in the rectifier circuits of various switching power supplies. This should be taken into account in the diagnosis and repair.
To eliminate voltage surges that are dangerous for Schottky diodes, which are formed in the transformer windings at the pulse fronts, so-called damping circuits are used. In the diagram, it is designated as R15C14 (see Fig. 1).
When analyzing the power supply circuitry of the Acer AL1716 LCD monitor, damping circuits were also found on the printed circuit board, consisting of smd resistor 10 ohm (R802, R806) and capacitor (C802, C811). They protect Schottky diodes (D803, D805).
Damping circuits on the power supply board
It is also worth noting that Schottky diodes are used in low-voltage circuits with a reverse voltage limited to units - several tens of volts. Therefore, if a voltage of several tens of volts (20-50) is required, then diodes based on a p-n junction are used. This can be seen if you look at the datasheet for the TOP245 chip, which shows several typical power supply circuits with different output voltages (3.3 V; 5 V; 12 V; 19 V; 48 V).
Schottky diodes are sensitive to overheating. In this regard, they are usually installed on an aluminum radiator for heat dissipation.
It is possible to distinguish a diode based on a p-n junction from a diode on a Schottky barrier by a conventional graphic designation in the diagram.
Symbol for a diode with a Schottky barrier.
After the rectifier diodes, electrolytic capacitors are placed, which serve to smooth out voltage ripples. Further, using the obtained voltages of 12 V; 5 V; 3.3 V supplies power to all units of the LCD monitor.
DC/AC inverter
In its purpose, the inverter is similar to electronic ballasts (electronic ballasts), which are widely used in lighting technology to power household lighting fluorescent lamps. But, there are significant differences between the electronic ballast and the LCD monitor inverter.
The LCD monitor inverter is usually built on a specialized microcircuit, which expands the set of functions and improves reliability. So, for example, the Acer AL1716 LCD backlight inverter is based on a PWM controller OZ9910G. The controller chip is mounted on a printed circuit board by planar mounting.
The inverter converts a direct voltage, the value of which is 12 volts (depending on the circuitry) into an alternating voltage of 600-700 volts and a frequency of 50 kHz.
The inverter controller is able to change the brightness of fluorescent lamps. Signals for changing the brightness of the lamps come from the LCD controller. Field-effect transistors or their assemblies are connected to the controller microcircuit. In this case, two assemblies of complementary field-effect transistors are connected to the OZ9910G controller AP4501SD(Only 4501S is listed on the chip package).
Assembly of field-effect transistors AP4501SD and its pinout
Also, two high-frequency transformers are installed on the power supply board, which serve to increase the alternating voltage and supply it to the electrodes of fluorescent lamps. In addition to the main elements, all kinds of radio elements are installed on the board, which serve to protect against short circuits and lamp malfunctions.
Information on repairing LCD monitors can be found in specialized repair magazines. So, for example, in the magazine “Repair and service of electronic equipment” No. 1 of 2005 (pp. 35 - 40), the device and the schematic diagram of the LCD monitor “Rover Scan Optima 153” are considered in detail.
Among monitor malfunctions, there are quite often those that are easy to fix with your own hands in a few minutes. For example, the already mentioned Acer AL1716 LCD monitor came to the repair table due to a broken contact of the socket outlet for connecting the power cord. As a result, the monitor turned off spontaneously.
After disassembling the LCD monitor, it was found that a powerful spark formed at the site of poor contact, traces of which are easy to detect on the printed circuit board of the power supply. A powerful spark was also formed because at the moment of contact, the electrolytic capacitor in the rectifier filter was charging. The reason for the failure is the degradation of soldering.
Solder degradation causing monitor malfunction
It is also worth noting that sometimes the cause of a malfunction can be a breakdown of the diodes of the rectifier diode bridge.
