27 Oct 2018
# MiTV black screen, faulty LED panel
https://tinyurl.com/y5kw24kz google: https://tinyurl.com/y6tcjx6t
This is a common complaint in MiTV and also in other makes. Some of these black screen faults are caused by OS updates; others are due to hardware component failures. The Power Supply Board is usually the culprit. This article intends to serve as a guide to troubleshoot this black screen problem, using MiTV4 as example.
The MB of MiTV4 contains the CPU, I/O devices and the interfacing components to work with the LDB to light up the LED panel. The PSB will supply 12V power lines to the MB which will do all the necessary startup and "instruct" the LDB, the indicators and the remote controls to work with the LED panel. The PSB also supplies the 96 Volt supply to power the LED backlights.
The following suggestions should help to troubleshoot the faults.
How To Repair the LED Backlights?
There is no repair video yet for repairing the backlight of MiTV4 series. In particular, the MiTV4 has a 9 mm thick LED panel, requiring Edge LED or ELED type of backlights to be installed at the bottom of the LED screen instead of installing it directly behind and underneath the LED panel (Direct LED or DLED).. Because of this, many users of MiTV have complained about the heat generated by the backlights at the bottom of TV.
However, here is good video about how to replace and test the LED backlights for common and traditional type of TVs with DLED. This could apply to other MiTV4 series such as MiTV4A etc
Usually, users were able to repair most TV problems by first replacing the power supply board, then follow by the Main board or logic display board in that sequence.
# MiTV black screen, faulty LED panel
https://tinyurl.com/y5kw24kz google: https://tinyurl.com/y6tcjx6t
This is a common complaint in MiTV and also in other makes. Some of these black screen faults are caused by OS updates; others are due to hardware component failures. The Power Supply Board is usually the culprit. This article intends to serve as a guide to troubleshoot this black screen problem, using MiTV4 as example.
How MiTV works?
MiTV has only a 3 components; the Main Board (MB), the Power Supply Board (PSB)and the Logic Display Board (LDB) or commonly known as T-Con board. The LDB Board is usually shielded inside a metal cover. Behind the plastic and metal covers, there are also other components such as Bluetooth receiver, the speaker modules and most important of all, the LED backlights. The following shows the layout and back panel of MiTV4; other models of MiTV are quite similarThe MB of MiTV4 contains the CPU, I/O devices and the interfacing components to work with the LDB to light up the LED panel. The PSB will supply 12V power lines to the MB which will do all the necessary startup and "instruct" the LDB, the indicators and the remote controls to work with the LED panel. The PSB also supplies the 96 Volt supply to power the LED backlights.
What can go wrong?
When there is black screen, it will involve faults in the PSB, MB and the also the LDB. If these component boards are healthy, then the fault could lie in the LED panel, meaning the interfacing board within the LED panel might be faulty. When this happen, the repair will be complex. Our 55" MiTV4 had a LED panel fault and was replaced during the 1 year warranty period.How to detect what went wrong?
The traditional wisdom is to shine a bright torch light as close as possible at the screen and at an angle to determine if there are moving images on the screen. In here, the torch light is simulating the backlight to check if the faulty backlight is the cause.The following suggestions should help to troubleshoot the faults.
Description | Possible causes and actions | Remark (Dbclick to enlarge video/pictures) |
I) No Moving Image and No Sound | ||
1. Power Indicating lights not on | 1) Make sure the power is plugged in and the remote control’s battery is good by replacing the battery 2) If still not working, press the white start button underneath and at the centre of the TV | Reference video found in YouTube for information (Click here for full screen) |
2. Indicating lights are on | Try to factory reset the OS by pressing the [Confirm] and the [Restore] at the same time and start the TV by pressing the white start button after powering off the TV for about 20 seconds | (Click here for more information on how to do a factory reset). |
3) The screen is still in complete darkness | If the TV has been synchronized before for screen mirroring, use the hand phone to check if it can locate the address to the TV | If cannot locate the address of the TV, most likely the TV is dead with faulty MB or PSB |
4) The screen is back | This screen will be shown on successful factory reset. | |
II) Got Moving images and got sound | ||
Suspect PSB has problem supplying power for the backlights Most likely the LED backlights are faulty. | (Click here for full screen) | |
III) No moving images but got sound | ||
Check the supply voltages to the LDB and PSB. Most likely a) The LDB is faulty or the LCD screen is faulty b) The PSB is faulty |
Flow Chart for the Repair
(Double click flow chart for full screen)
Why the Power Supply Board (PSB) can be Faulty?
The Power Supply Board supplies not only power to the MB but also the power to the LED backlight directly. When instructed by the MB, a high voltage (96 volts for 55" MiTV4) will be sent to the LED backlight to light up the screen. If there is a faulty LED, this 96 Volt power rail will be short circuited and this may damage the PSB. The LED strip's PCB rail could be burnt off, resulting power not being supplied to a strip of LEDs as shown in the following picture.How To Repair the LED Backlights?
There is no repair video yet for repairing the backlight of MiTV4 series. In particular, the MiTV4 has a 9 mm thick LED panel, requiring Edge LED or ELED type of backlights to be installed at the bottom of the LED screen instead of installing it directly behind and underneath the LED panel (Direct LED or DLED).. Because of this, many users of MiTV have complained about the heat generated by the backlights at the bottom of TV.
However, here is good video about how to replace and test the LED backlights for common and traditional type of TVs with DLED. This could apply to other MiTV4 series such as MiTV4A etc
Usually, users were able to repair most TV problems by first replacing the power supply board, then follow by the Main board or logic display board in that sequence.
How to Prolong the life of LED backlights?
Users have been advised to lower the brightness of the TV to about 50% to 75% so as to reduce the heat caused by the LEDs backlights. Having proper ventilation at the location where LED backlight is located will prolong its life.Where can we buy the MiTV Spares?
MiTV spares are often offered for sale in TaoBao as the vendors stripped old broken TV set to salvage the parts. They would usually test the boards and give 90 days warranty or money back if the board can be returned within 7 days. However, it is always good to ensure that one would not be cheated when buying stuff from TaoBao.If one cannot find the spares in TaoBao, it may be because the MiTV is quite new and one might have to wait for a while.
The Boards of 55" MiTV4
The following pictures are taken from a 55" MiTV4 . When ordering the part, give the vendors the correct parts number copied directly from your TV.
The Main Board | The Power Supply Board | The Logic Display Board (Different for different panel makers) |
The remote Control Board | LED strips w/o alum panel | LED strips inside alum panel |
Speakers and Remote control | ||
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