Repair Of CRT TVs: Do-it-yourself Frame Scan Of CRT TVs. Malfunctions Of TVs With A Kinescope

2024 Author: Beatrice Philips | [email protected]. Last modified: 2024-01-15 04:10

The TV is one of the most widely used devices of frequent use, found in almost every home. CRT TVs or, as they are abbreviated as they are called, CRT TVs are distinguished by their reliability, durability and are popular to this day. Over the years, they have truly become a traditional feature in the living rooms of many families. These are the same "old" TVs that have served flawlessly for decades and eventually acquire the status of almost a "family member". What to do if the "favorite" is out of order? Is it possible to repair it yourself? Where should you start troubleshooting? Let's figure it out.

Breakage signs

Before proceeding with the repair, you need to make sure what the problem is, what are its symptoms. The most important and expensive part of CRT devices is the CRT tube.

The quality of the image displayed on the screen directly depends on the operation of this part. The correctness and duration of the operation of the kinescope is due to the operating conditions.

It is extremely important for users of such TVs to ensure that the voltage on the electrodes exactly corresponds to the technical parameters specified in the instructions. There are only a few classic signs of breakdown that indicate a failure of one or another element in the TV system.

The technique does not turn off . This is one of the most popular situations faced by both CRT and modern LCD models. This problem is related to the fuse, which tends to blow. However, different models have different details. The reason can also be hidden in the diode bridge. You need to check if it has burned out.

Screen color changes while watching channels , unnatural color spots, sometimes colored horizontal or vertical stripes, may appear. All these are signs of a malfunction of the posistor, or rather, the strong magnetization of the kinescope.

TV does not turn on or turns on , but turns off on its own after a while, the indicator blinks or does not light up. This problem occurs in the case of power surges in the electronic network.

There is an image, but there is no sound . This is a sure sign that your speakers are not working properly. The sound sometimes cuts through and pops from time to time. A power failure or a radio link failure may occur.

The device does not respond to commands from the remote control . Most likely, the failure is associated with a defect in the remote control itself. You may just need to change the batteries. Less often, the photodetector or the microcontroller of the TV, which processes the commands of the remote control, fails. This case requires the hand of a master, who will have to diagnose the device in order to determine the cause.

Channels are missing … This is a symptom of malfunctioning television receivers. This "ailment" can be corrected by auto-tuning or manual tuning according to the instructions. If, after all, the situation does not change, and the TV cannot find any channels, and instead the screen displays “no signal” or just a noise saver, there may be something wrong with the high-frequency circuit or tuners that are responsible for converting electrical signals.

Major malfunctions

As a rule, during a visual inspection, it is not always possible to identify what exactly broke on the TV, which part is out of order. In this case, you need to start diagnosing the internal system from the power supply. Its verification is carried out by analyzing the supply voltage, load voltage, integrity and correct functioning of the main supply circuit and the feedback circuit, which is designed to control and stabilize the voltage. It is necessary to check electrolyte capacitors, the capacity of which decreases significantly and becomes narrowed when dry, which leads to malfunctioning of the entire power circuit.

Checking the horizontal scan can show that the defect is hidden in the operation of the output stage or the output transistor of the horizontal scan.

Checking the vertical sweep indicates problems with the power supply of the electrical oscillator and the output stage . To check the power supply circuit of the kinescope, you need measure the degree of its glow . When a fairly high voltage occurs it is enough to check the integrity of the filament heating the cathode of the kinescope for its operation.

Checking the video amplifier, screen backlighting system, color block and matrix is needed if sound and image disappear on the TV. This means that there is something wrong with the supply voltage of the radio channel or the tuner and the HCV is not functioning correctly. If there is sound, but there is no picture, then this is a video amplifier and a color block. If there is sound, but there is no picture, then these are audio circuits or a bass amplifier.

Checking the control unit: you need to make sure that the processor is receiving power, analyze the level of its voltage ripple . You should also check the operation of the clock generator, trace the signal flow from the receiver to the processor, and pay attention to the presence of polling pulses and their supply to the control bus. If there are problems with tuning channels, then usually the matter is in a malfunction of the television receiver unit.

Self repair

At the outset, it should be noted that a CRT, like any other TV model, is fragile and complex technical scheme . You must be patient to repair the receiver yourself. The utmost care and attention is also important. One wrong, unconscious movement, and the kinescope can be damaged, as a result of which replacement with a new one will cost about 70% of the cost of the TV itself.

The first thing to do is find out exactly where and how the breakdown manifests itself and what are its "symptoms ". This will significantly save your time and save the device from unnecessary disassembly and rotation of the board. Before you decide to disassemble the TV, its preliminary diagnostics must be carried out.

Disassembly should start from the rear protective cover . By unscrewing the screws, you will see a complete picture of the "insides" of the TV. When removing the lid, it is important not to touch or hit the tube of the kinescope, on which the board with the elements is installed.

Sometimes you are surprised how much dust collects inside the cabinet, which must be removed using a small brush that will not damage the inside of the TV.

Recommendations

Repairing a CRT is difficult . Only after finding out the individual breakdown, making sure that this particular element is out of order, after conducting preliminary diagnostics, you can start repairing the TV with your own hands. If you are not completely confident in your abilities, it is better not to waste time and turn to specialists. Before the arrival of the master, do not forget to check and exclude the following commonplace situations:

• lack of electricity in the room;
• make sure that the plug of the TV receiver is connected to the outlet;
• remove dust deposits on the TV screen.