Regardless of the brand of LED TV, its simplest malfunction is manifested in the fact that it stops turning on. This is often accompanied by a complete absence of any signs on the front panel, and sometimes the LED built into it blinks and immediately goes out. At the same time, sounds unusual for LED TV can be heard, reminiscent of buzzing, whistling and short clicks.
REASONS FOR MALFUNCTION
The algorithm for finding such a problem is well debugged. According to him, one should start with external reasons, when identified, the following are checked:
- The presence of mains voltage.
- Serviceability of the power cord.
And only after making sure that all these factors have nothing to do with it - you can proceed to internal problems.
Important! Their search is associated with opening the cover of the TV receiver and access to its expensive electronic units.
In the case when there is no self-confidence, it is wiser to seek help from specialists. Let us consider in more detail the procedure for examining external causes.
If, after replacing it, voltage is still not supplied to the internal circuits, you should proceed to checking the fuse You can simply remove it from the holder (with the plug unplugged) and ring the tester for a break. If it turns out to be faulty, you will need to replace it with a new one (3.15 Amperes), after which the TV on indicator should light up IF NOTHING ELSE IS WRONG.
DIAGNOSING A MALFUNCTION BY A WORKING INDICATOR:
When diagnosing LED TV, they proceed from the state of the indicator, the operating mode of which determines the nature of the malfunctions that have occurred. Let's consider the situation in more detail.
INDICATOR FLASHES
Blinking continuously means the TV is in self-diagnosis mode. The type of malfunction is judged by the number of flashes of the red light during the observation time after turning on the TV. To identify the cause corresponding to the observed number of flashes, you need to take the instruction manual and find the section "Malfunctions and their indication".
Based on this data, you can draw up a plan to find the cause and then follow the instructions in the document.
- THE INDICATOR IS ON CONTINUOUSLY
The presence of a constant light of the LED means that power is supplied to the control unit (CU). If the TV does not react in any way to pressing the buttons on the remote control, you need to try to turn it on using the buttons on the setting panel. If such an attempt is successful, the cause of the problem is an inoperative remote control. Therefore, NOW, you should proceed as follows:
- Check the contact terminals and the health of the batteries.
- Make sure that the IR emitter is working and the buttons on the remote control panel do not stick.
- If they fail when pressed, the remote control must be disassembled and cleaned from dust.
- If, after all the manipulations, the remote control does not show any "signs of life", it should be replaced with a new, original product.
If you also cannot start the TV from the control panel, there are two options, discussed below.
PROTECTION
When the protection is triggered, a situation is observed when the TV tries to start, but, after a couple of seconds, the screen suddenly goes out, and then does not light up anymore. The reason for this is most often the poor quality of the supply voltage (its dips are below the permissible level). To resolve the problem, you should disconnect the TV from the mains (pull out the cord) and wait a while.
Additional information: If you have a tester, you can check the mains voltage and make sure that it is restored or, conversely, that it has completely disappeared.
Wrong switch-on mode selected
If the TV for any reason goes into standby mode, it will automatically turn off the display, which outwardly looks like its malfunction. In this case, you just need to take the remote control and change the mode by pressing the "Standby" button. In this case, the TV's power supply does not completely turn off, that is, it is always ready for use.
The lack of display luminescence may be due to the disabled function of viewing various channels (including cable) through the AV and HDMI interfaces. This can also happen due to the disabling of the necessary settings when working with a laptop. To fix the situation, you just need to restore them.
- THE PRESENCE OF EXTRANEOUS SOUNDS WHEN TURNED ON (INDICATOR IS ON)
If, when you turn on the TV, the indicator lights up, but the screen does not, and all this is accompanied by specific clicks or buzzing, the matter is most likely due to a malfunction or overload of the power supply. This can be verified by a simple inspection of the electronic module, individual elements of which may have a burnt appearance.
You should not change them immediately; first it is necessary to identify the CAUSES OF OVERCURRENT. To do this, one should disconnect all the circuits connected to it one by one and fix the state in which the hum and clicks in the PSU disappear
Important! Since the circuit for switching on loads contains many locks, if it is impossible to independently identify the exact cause, it is recommended to seek help from professionals.
In conclusion, note that the most unpleasant and costly situation is when the matrix and backlighting elements are burnt out. It manifests itself in the absence of characteristic flares on the panel or in the appearance of cracks on it in the form of a fine mesh. In this case, there is only one way out - to completely replace the burnt matrix with a new product.
- LCD TV POWER SUPPLY - DEVICE, PRINCIPLE OF OPERATION, POSSIBLE MALFUNCTIONS AND METHODS OF THEIR ELIMINATION
The power supply unit of a modern TV set (TV), regardless of the brand of its display, is a pulse voltage converter with fixed output characteristics. Their normalized values determine the normal operation of the entire device as a whole. In the event of any malfunctions, by their change, one can judge the nature of the breakdown.
- DEVICE AND PRINCIPLE OF OPERATION
A switching power supply (SMPS) board is often made in the form of a separate electronic module, which is a characteristic feature of a TV with a small screen diagonal. In larger models, it is integrated into the chassis of the receiver and is located inside its structure (see photo below).
The power supply board includes the following mandatory components:
- Pulse transformer.
- Line supply filter based on chokes and capacitors.
- Duty and working mode nodes.
- Overload protection module.
- Cooling elements (radiators).
The principle of operation of the PSU is to bring the mains voltage to a form that meets the power supply requirements of the main electronic components of the TV (including its matrix).
ADDITIONAL INFORMATION: THE MAGNITUDE AND SHAPE OF THE SUPPLY POTENTIALS MUST CORRESPOND TO THE OPERATING VOLTAGES AND THEIR DIAGRAMS GIVEN IN SPECIAL TABLES.
Sometimes they are indicated directly on the electrical diagram of a particular device.
Typical malfunctions and their identification
Let's consider typical faults of the power supply using the example of a TV with a LCD screen. Their external manifestations are expressed in the following deviations from the normal operating modes of the reproducing device:
- When you press the "POWER ON " button, the TV does not turn on at all.
- The indicator is on, but the TV does not switch from standby to operating mode.
- The image appears only after a while.
- It is possible to turn on the TV only after a few attempts, after which a normal picture and sound appears.
The first thing that begins with the survey when most of these faults are found is a thorough visual inspection of the power supply board with the device completely disconnected from the network. If nothing suspicious is found, you should proceed to a more detailed analysis of the reasons for their occurrence. To do this, you will need to dismantle the power supply module from the TV case, first disconnecting all the connectors.
Then it is necessary to discharge the high-voltage filter capacitor of the power circuits, the residual voltage on which is dangerous to humans. In the power units of most TV models, including this one, the causes of malfunction are most often:
Failure of electrolytes of secondary supply circuits.
Poor soldering of individual components of the board (chokes and semiconductor elements, in particular).
Burnout of power (key) transistors.
Breakage or loss of contact in the supply connectors.
PLEASE NOTE: IT IS POSSIBLE TO MAKE SURE THAT THE ELECTROLYTES ARE OLD AND OUT OF ORDER BY THEIR SWOLLEN LID (PHOTO ABOVE).
The consequences of poor voltage filtering due to their failure are very different. They are manifested either in the complete loss of the power supply's performance, or in the associated damage to the inverter elements. Often they lead to software failure in the motherboard memory chips and the need to update it.
The rest of the faults are also detected visually. When transistors burn out, for example, in the area of their legs, we can clearly distinguish a black coating of burning. Periodic loss of contact in the connectors is determined by its restoration with a slight sway from side to side. To carry out such a test, you will need a tester included in the “Callback” mode. In other cases, malfunctions are detected by the loss of the required output voltages (or their deviation from the norm).
Trouble shooting
- THE GENERAL PROCEDURE FOR DIAGNOSING AND ELIMINATING DETECTED FAULTS IS REDUCED TO THE FOLLOWING SEQUENCE OF REPAIR OPERATIONS:
- All capacitors whose appearance raises at least some suspicion must be replaced immediately.
- In case of a malfunction of the standby unit, check the 5 Volt voltage on the controlled zener diode.
- If at the output of this unit there is no voltage on the filtering capacitors or its value is greatly underestimated, this means that the operating mode is violated.
- To restore it, you will need to make sure that all linear elements of the circuit are in good working order.
ADDITIONAL INFORMATION: THEIR PERFORMANCE IS CHECKED USING THE SAME TESTER WITHOUT COMPLETELY DESOLDERING FROM THE BLOCK BOARD.
To do this, it is enough to remove only one contact of the "suspicious" resistor or capacitor. Identified burnt elements are removed from the board completely and replaced with new ones. If poor-quality soldering is found, this place should be tinned with flux, and then make sure that the contact leg is securely fixed in the fixing zone.
The restoration of the operability of the standby circuit is evidenced by the appearance of a voltage of 5 Volts, as well as the lighting of the red LED on the front of the TV (photo above).
- At each next replacement of other "suspicious" elements, you should immediately check the changes that occurred at the output of the power supply unit. The restoration of the function of the operating mode, for example, is judged by the normal turning on of the TV and the appearance of images and sound on its screen.
In conclusion of the review, note that identifying and troubleshooting the switching power supplies that are part of modern television receivers is a completely difficult procedure. It requires special measuring equipment and some skills in the repair of electronic equipment. If you find it difficult to diagnose the cause of the TV failure on your own, it is best to invite a professional TV master. With the current, relatively low cost of repairing television equipment, this will save time and not waste your EFFORT.