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As an important entertainment device in our daily lives, televisions occasionally experience various faults. These faults not only affect our viewing experience but may also render the television unusable. Below, I will share a summary of common television faults and repair methods.
01Various Faults in LCD TVsWith the advancement of time and technology, LCD TVs have become a very common household appliance. LCD TVs are high-tech products, which means that once quality issues arise, repairs can be quite troublesome. Common minor faults in home LCD TVs include failure to power on, no sound after powering on, or image issues, etc. So how should we repair these problems? What are the repair costs?This article will provide a brief introduction!1. Common Faults in LCD TVsNo sound, no imageIf the television shows no sound, no image, and the power indicator is off after powering on, the first factor to consider is a problem with the power board. Another possibility is that the CPU part of the television is not functioning properly. If during use, the television powers on with no sound and image, and the power indicator flashes once before staying on, while a white light flashes at the moment of powering on, the fault may be due to a damaged backlight driver board, but it could also be caused by issues with the backlight lamp itself.Power-on issuesIf the television light flashes but does not power on, this fault may indicate that the CPU bus is not functioning properly or that there is poor contact with the LCD TV’s IC. If the LCD TV powers on but has no light and sound after a while, it is generally due to a fault in the inverter circuit of the TV screen assembly, or it could be due to aging or damage to the TV’s light tube, which causes the high-voltage board to protect itself.Display issuesIf the television displays a full screen of noise or regular vertical stripes, it is generally due to a problem with the buffer board. In this case, during LCD TV repairs, one can replace a pair of buffer boards or measure which IC line has failed and then replace it accordingly.2. LCD TV Screen IssuesBlack screenBlack screen situations are quite common, including image interference and partial black screens. When a black screen occurs, the first step is to check if the mainboard program is missing; if so, simply rewriting the program can resolve the issue. Next, check if the chip is damaged; if it is, a new chip needs to be replaced and the program rewritten.Color distortionColor distortion refers to the television screen still displaying images with sound, but the images are incomplete, with sudden color blocks appearing, making it impossible to watch normally. In such cases, one should first check if the mainboard clock output is normal, whether the mainboard’s three-color signal output to the main chip has faults, and whether there are any short circuits in the connections from the mainboard signal output to the screen.3. LCD TV Repair CostsRepair costs for LCD TVs without board replacement generally start at around 100+, depending on the size of the TV. Replacing the entire mainboard typically costs around 300-500 yuan. Merchants should not charge a service fee during the warranty period; if the product is beyond the free warranty period, charging a service fee for repairs is reasonable. Currently, there are no mandatory regulations for appliance repairs in the country, so companies often follow their own standards. Consumers should clarify the repair service items and costs when accepting appliance repair services, check the price list or catalog, and request the replaced original parts and detailed repair service receipts to protect their legal rights.Below, I will share some common faults based on my own experiences, including various TV repair techniques, cases, and insights!
- TCL LCD 2026A powers on with normal image but garbled characters.
Fault analysis: The device does not have a menu zoom function. If the user has enabled the menu zoom function, garbled characters will appear. Press the number keys 3210 on the remote to enter the factory menu, turn off the zoom function, and exit.I encountered three new 26-inch LCD TVs of the same brand and model, where the AV input from the DVD worked perfectly, but when connected to a DVB satellite receiver, the image showed interference patterns, similar to poor contact with the video cable or socket, while the sound was normal. Testing with other video cables and receivers yielded the same result. It is unclear whether the LCD TV has weak anti-interference or the receiver has strong interference. Ultimately, after testing, I connected the TV’s high-frequency head to the receiver’s RF output socket using a coaxial cable, and the interference pattern disappeared. Any insights on this would be appreciated.A Changhong 42-inch plasma TV had interference patterns when powered on using a set-top box, but not when using a DVD (same socket). There was no interference when using RF. Eventually, I found that plugging in a video cable to another socket eliminated the interference. TCL-LCD20B66 had no sound. Upon powering on, both TV and AV had no sound. Injecting interference with a multimeter produced sound. Short-circuiting the audio processing 1142 signal input/output could hear a faint sound, but replacing 1142 did not resolve the issue. Measuring 1142’s voltage was normal, suspecting a software fault, I entered factory mode, and the SOUNDSETTING data was 0. After changing it, it worked normally.An LG LCD monitor reported a buzzing sound, indicating a power board issue. After replacing the power supply, it worked normally (under warranty). However, upon return, the user reported it still buzzed, but differently, now intermittently. Upon inspection, I found a ground leakage issue, and after replacing the power strip, it worked normally. However, upon return, the user reported the same issue again. I ordered a new board from the manufacturer, and after replacing it, it worked normally. The main reason for the two repairs was the user’s power strip issue. I wonder if anyone has any insights on this.
- Changhong TM150A1 LCD TV fault: Powers on with no response, and the indicator light is off.
First, measure if there is 12V DC voltage at pins 5-8 of NP03; if not, unplug the adapter and measure if there is 12V DC voltage at the adapter’s output; if there is, measure the internal power NP02 and NP01’s resistance to ground (should be 1.3 kΩ and 1.5 kΩ respectively when normal); if normal, measure the resistance of NP03’s pins 5-8 to ground; if abnormal, unplug XSP5 (the inverter power plug) and measure NP03’s pins 5-8 to ground again; if still abnormal, it can be determined that there is a short circuit in the VSl2 power supply load. In actual repairs, it is often due to a faulty NA91 (TDA8425); replacing it resolves the fault.
- Xiahua LC37T25 sometimes has a black screen on startup.
Fault inspection: When powered on, both image and sound are present, but after about 20 to 30 seconds, a black screen appears. Upon opening the cover, I found that when the black screen occurs, the backlight turns off. Measuring the backlight power supply at 120V was normal, but measuring the backlight switch control pin voltage showed it fluctuating (normally this control voltage should be high). To distinguish whether the issue is with the backlight board or the mainboard, I unplugged the control line from the mainboard to the backlight board and directly measured the mainboard’s backlight control pin, finding that this pin’s voltage fluctuated. Thus, I determined that the mainboard was faulty, and after replacing it, the fault was resolved.
- Xiahua LC-37HU19 powers on with backlight but no image, sound is normal.
Fault inspection: This fault is likely caused by a faulty logic board. After replacing the logic board and powering on, the fault persisted. I then replaced the mainboard, but the fault remained. After considering, I wondered if the LVDS cable was the cause, so I applied for a new LVDS cable. Once it arrived and was replaced, the machine powered on normally; thus, I concluded that a faulty LVDS cable could also cause the backlight to turn on without an image while sound is normal.
- A Skyworth 22L10IW LCD TV has sound but no image, resulting in a black screen.
Upon inspection, I found that the screen driver circuit’s power supply resistor was open, preventing 12V voltage from passing through, resulting in a black screen. Replacing the resistor or reconnecting it resolved the issue.
- Samsung LA32M61B LCD TV can power on normally but can only receive the channel that appears at startup; the remote and panel buttons only work for the last two buttons, while channel adjustment and volume control do not work.
After opening the back cover and unplugging the button board connector, the remote worked. Checking the connector’s three pins, one was grounded, the second was 3.8V, and the third was 1.8V (this voltage supplies KEY2, V+, V-, P+, P-). This voltage is definitely low, causing this part to malfunction and also affecting the remote control. This connector is connected to the CPU, and there are not many external components. I analyzed that there might be an issue with the CPU’s KEY2 input pin. After discussing with the owner, we decided to use the remote control without the panel buttons. Although it was a temporary solution, it saved the cost of replacing the CPU and was not a major issue! I noted this for everyone’s reference!
- Xiahua LC37T25 sometimes has a black screen on startup.
Fault inspection: When powered on, both image and sound are present, but after about 20 to 30 seconds, a black screen appears. Upon opening the cover, I found that when the black screen occurs, the backlight turns off. Measuring the backlight power supply at 120V was normal, but measuring the backlight switch control pin voltage showed it fluctuating (normally this control voltage should be high). To distinguish whether the issue is with the backlight board or the mainboard, I unplugged the control line from the mainboard to the backlight board and directly measured the mainboard’s backlight control pin, finding that this pin’s voltage fluctuated. Thus, I determined that the mainboard was faulty, and after replacing it, the fault was resolved.Recently, I repaired a Hisense 42-inch LCD TV with a black screen and sound. Upon checking, I found no 24V output, but everything else was normal. I discovered that the 24V power transistor and a nearby 2KV capacitor were faulty. This power transistor is not available in the local market, so I tried using a universal power module for regular TVs as a replacement. After replacing the capacitor and securing the module to the heat sink, I connected the red wire to the power supply, the black wire to ground, and cut the green wire, connecting it to a light bulb to adjust the power output to 24V. After restoring the circuit and testing, everything worked normally.
- Samsung LCD TV LA26R51B has sound but no image and no light; upon opening the back cover in a dark room, the backlight does not light up after powering on.
Thus, I checked the high-voltage board. This model uses 8 light tubes, and the high-voltage board outputs 24V in two paths, each with a 4A fuse resistor, with one path connected to 4 light tubes. Upon inspection, I found that one of the 4A fuse resistors was open, while the other path was shorted. This caused the fuse resistor to open. That path had four MOSFETs, and upon disconnecting them, I found that two of the MOSFETs were shorted to ground, model SP8M3. After removing the two faulty ones and testing, the screen lit up but then went out, confirming that the damaged MOSFETs caused the protection. After replacing the two MOSFETs, everything worked normally.Xiahua LC-37HU19, AV1 has no input. Upon disassembly and inspection, I found that the AV switching circuit is on the analog board component. The AV channel consists of the AV socket, NB102 (SMD ICPESD5VL4UG)/NB101 (SMD IC PESD5VOL5UY), and NW200 (SMD IC HEF4052BT0). Among them, NB101 is the audio channel for AV1 and AV2, while NB102 is the video channel. After passing through NB101 and NB102, the signals are sent to NW200 for image and audio switching. Therefore, after replacing NW200, the fault persisted. After replacing NB102, the fault was resolved.The above is about common issues with LCD TVs and how to repair them.I hope this can be helpful to everyone!