【 Weak current College 】 LCD video troubleshooting

Trouble phenomenon: early friends replace a 15 inch LCD monitor, model is AOCLM-500 has been used quite normal. But just over half a year, this LCD monitor that has failed, as evidenced by: as long as start or restart the computer, it will appear similar to the "video" of the symptom, gives the impression as if there is a high-frequency electromagnetic interference, the writing on the screen very vague and jagged. When entering the Win98SE, occasionally this symptom, but duration is very short and not too obvious, most of the time display is normal.

Troubleshooting: first replace a graphics card, find fault persists. Followed by a good 17 inch CRT flat screen monitor to replace the exclusion test, no similar failures.

LCD monitor failure analysis: digital interface (DVI) is the best LCD display interface. But the video card manufacturer for cost reasons, the video card generally do not have a digital interface, and through the internal conversion of digital/analog circuit and the video card is connected to the VGA connector. This connection form although solves the problem of signal match, but it also brought a vulnerable to interference and distortion. The reason for this is mainly because the LCD itself is very difficult for the clock frequency and input analog clock frequency synchronization to maintain 100 percent, especially in the analog sync signal frequency changing, if this LCD monitor synchronization circuit, or is connected with the video signal transmission line of a short circuit, bad, and not be able to adjust the follow up to maintain the necessary synchronization relationship, they will encounter in this article to start displaying exceptions, and enter the system and displayed normal strange symptoms.

Accordingly, the judgment of the failure point is likely to be in flat panel LCD monitor internal synchronization circuit or connection interface pins and transmission cables.

Resolution: consideration to LCD monitors internal synchronization control circuit is normally set in the Interior of a piece of integrated circuits and integrated circuit damage unlikely. They will check the focus in the interface pins, transmission cables, as well as synchronization circuit for over adjustable components.

First LCD Shell opened, exposing the internal connection cable, digital multimeter to pass or not pass check beep, one by one to check the connection pin and the corresponding cables breakover, didn't find any circuit, short circuit, and other physical connectivity problems. Then along the cable connector of the trend, find the printed circuit board input control circuit unit and discovered in the 14 foot package integrated circuit block edge installation has two micro-adjustable potentiometers, a printed circuit board labeled WR604, another for WR1201. The author based on past experience in maintenance of CRT monitors preliminary judgment, the two micro-adjustable potentiometers, is likely to be used to synchronize the fine-tuning, however which one has a problem? in order to secure and remove the number of LCD shell, I use absolute alcohol will be two and a half adjustable potentiometers all cleaning and wiping it, alcohol all volatile will LCD shell recovery after power on the machine and found that although failure reduction, but successive boot process failures sometimes inconsistent. But once again opened the LCD monitor of the shell, with a miniature cross screwdriver WR604 clockwise adjust slightly, then recovery shell and power up the test again, the LCD displays are displayed correctly, so far, troubleshooting.

Slightly adjusted while it is possible to make the LCD monitor temporarily restore normal work, but as an extension of time is of the view that the failure is likely to be repeated. Therefore, considering the fundamental solution or to replace a semi adjustable potentiometers. Unfortunately this is how much grain deal mung bean semi adjustable potentiometers in ordinary electronic market is difficult to buy, I also has not decided otherwise.