An indication of the operation of the television device is provided by a two-color LED that shines green when the TV is on, and red when it is off from the remote control. The color scheme was chosen a very long time ago, since the time of kinescope TV, although now manufacturers do not always adhere to these colors using others, in particular, blue emitters. What should I do if at one fine moment we don’t see an indication of its status on the front panel of our TV, while the device does not want to turn on?
Power Supply Diagnostics
There is no single answer to the question in such a situation. Most often, the defect is localized in the power supply, but not always. Only the measurement results and their analysis will allow you to set the correct direction in the further search. Typically, the TV power supply can be in two states: standby and working. In standby mode, the unit works at its best, providing the necessary voltage for the Stand-by processor, memory and photodetector, that is, those devices that are ready to execute a user command from the remote control or from the buttons on the TV panel.
If the voltage of the standby mode is absent or significantly differs from 3.3 or 5.0 volts (standard values in most models), efforts in further diagnostics should be directed to troubleshooting in the standby mode circuit of the unit itself. The main elements of the circuit are a PWM controller, a powerful field-effect transistor, and wiring and feedback elements. For self-repair, you must remember that the mains capacitor. the largest electrolyte on the board. can hold a charge for a very long time. Careless movement, inattention can lead to electric shock or failure of the measuring equipment. It is necessary to remember the axiom: "Discharge the line capacitor even when the TV is unplugged". You can protect yourself by shorting the conclusions of this part through a conventional incandescent lamp with wires soldered to it.
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If there is voltage at the output of the power source, it is necessary to diagnose and analyze the modes of the motherboard. In most cases, the voltage coming from the power supply is converted to other nominal values with the help of several DC-DC controllers, allowing to obtain the voltage values necessary for the normal operation of a number of elements of the motherboard. This primarily concerns the components responsible for interacting with the local keyboard, remote control and designed to execute user commands to change the state of the device.
If the voltage level of the converters on the main board shows a nominal match, but there is no indication, this indicates a violation of the functional state of the above devices or a failure of their software. Quite often, such a malfunction occurs due to flash drive microcircuits, most often SpiFlash, made in budget models based on Winbond 25q32bvsig chips and the like. The defect is diagnosed by monitoring the exchange of information between the chip housings using an oscilloscope. It is not easy to independently diagnose the motherboard at home.
A malfunction of the TV associated with the lack of an indication of its status when the power supply is working, most often indicates that one of the memory microcircuits is out of order and requires replacement or flashing. Our service offers the restoration of the performance of TVs using firmware and installing the original software on several types of programmers for many models of modern TV. The only limitation is that we do not repair warranty equipment and do not have the appropriate firmware databases for new models. This limitation is the result of a ban on manufacturers distributing technical information to warranty devices. Information is available only to authorized service centers for a particular brand of electronic and household appliances.