This week, we share a case analysis:
Title:
Skyworth 32E55HE Color LCD TV Malfunction
Engineer Name: Zhang Chenhao
Device Name: Color LCD TV
Device Model: 32E55HE
Serial Number: N.A
Malfunction Phenomenon: Repeated Restarting
Abstract
This color LCD TV is used for central monitoring display, summarizing and displaying data information from multiple monitors in real-time. This article introduces the structural composition of the Skyworth 32E55HE color LCD TV and investigates the repeated power-on and restart malfunction of the main unit based on the device’s operating principle. By replacing the LD1117 voltage regulator chip, the device was restored to normal operation. During the troubleshooting process, we based our analysis on the device’s working principle, modularly analyzed, located the cause of the malfunction, identified the faulty components, and ultimately restored the device to normal operation. We hope that the repair approach discussed in this article can inspire many clinical engineers in their daily work.
Keywords: Skyworth 32E55HE color LCD TV, repeated power-on restart, LD1117 voltage regulator chip.
Introduction
The Skyworth 32E55HE color LCD TV is mainly composed of a power board, main board, speakers, LCD display, and other components. The video signal is input through HDMI or VGA interfaces. After the video signal is input, the TV decodes the signal, scales it to the appropriate aspect ratio, processes the picture quality, and ultimately converts it into a signal that the screen can accept, presenting the image through an OLED screen, LCD screen, or laser TV.
We hope that the method of handling the malfunction discussed in this article can inspire many clinical engineers in their daily equipment maintenance work.
Fault Case
1.1 Fault Phenomenon
The device powers on, the indicator light turns green, the screen lights up, displaying the Skyworth logo, then immediately goes black, the indicator light turns red, and then the indicator light turns green again, the screen lights up, repeating this restart cycle, unable to enter the main TV interface.
Figure 1 Internal View of the TV
1.2 Fault Analysis
The fault may involve components including the power board and main board.
(1) After opening the back cover of the TV, the power board is on the left side, and the main board is on the right side, as shown in Figure 1.
(2) Power on the device and use a multimeter to measure the voltage output from the power board to the main board and the startup voltage output to the display. Throughout the automatic restart process, the 24V, 12V, and 5V voltages are all normal and stable.
This rules out power board faults.
(3) Check for any abnormalities in the components on the main board. Use a multimeter to measure the voltage starting from the power input of the main board, measuring the voltage conditions of each module in different areas. The main board is shown in Figure 2.
Figure 2 Main Board of the TV
(4) Upon inspection, the main board is roughly divided into three major parts: memory section, CPU section, and data transmission section. Power on the device, and when the TV light is green, measure the power supply status of these three areas, looking for any voltage anomalies when it turns red and restarts.
(5) When measuring the memory module, it was found that the input voltage of the voltage regulator chip was stable at 5V under both conditions, but the output was 1.59V when the green light was on, and briefly jumped to 2.35V when the red light was on, then stabilized back to 1.59V. As shown in Figure 3.
The capacitance values measured around it all met the standards, and it was basically determined that the issue was with the voltage regulator chip. The voltage regulator chip is shown in Figure 4.
Figure 3 Voltage Comparison Chart
Figure 4 LD1117 Voltage Regulator Chip
1.3 Fault Troubleshooting
After replacing the faulty LD1117 voltage regulator chip with a new one of the same specifications, power on the device, and it starts normally, successfully entering the TV channel interface. After observing for a while, there was no restarting phenomenon, and the fault was resolved.
Conclusion
Repair Insights:
The conclusion of the fault is that the LD1117 voltage regulator chip was damaged, causing the screen to light up normally after powering on, but during the system startup, the power supply to the memory module was abnormal, leading to system startup failure, automatic shutdown, and restart.
By modularizing the circuit, from large to small, the fault point will eventually be exposed.
Source: Zhang Chenhao
Editor: Yu Yali
Reviewer: Zhang Huihui
Statement: This article is an original piece. If you need to reprint or quote any text and images, please contact us! If for commercial use, violators will be held accountable!
Click the blue words
Follow us