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General Failure Analysis Guide

Any General Touch touch product can be divided into two function systems. One is the touch system, the other is the display system. This guide describes the common technical failures found with the touch and display systems, which you may encounter when using our products, and provides the corresponding solutions. If the failure has not been fixed after adopting the solutions contained in this guide, please kindly contact our technical support (service@generaltouch.com).

  Failure in Touch System
Failure Description: Touch Function Problem (Fail Touch Screen/Fail Touch Controller)

1. No Touch Function On the Whole Touch Screen
Excluding the possibilities of incorrect connections of cables or either a defective RS232 port or USB port of the PC, we need to get the status of the controller LED. You can see the controller LED via the holes on the back cover or the shielding cover. The normal status should be:
1) When powering on the controller, the LED will increase in brightness for 5~10 seconds and then the LED will go into the standby status, and will twinkle every 2 seconds;
2) When you touch the screen, the LED will brighten;
3) If you are not touching the screen, the LED will be dim;
4) After a significant period of time without touch, The LED will go back to the standby status and will twinkle every 2 seconds.
If the LED stays dim, the reason may be failures from the controller, from the communication cables, or from the wire board. To perform a swapping test is very helpful in confirming the failure. The possibility of defective communication cables or a defective wire board is relatively unlikely.
If the LED keeps twinkling every 2 seconds no matter whether a touch has been placed on the screen or not, the cause may be failures from the touch screen, from the communication cables, or from the wire board.
If the LED twinkles very fast, it indicates either that there may be a defective touch screen or controller, or that there may be a synchronisation problem between the touch screen and the controller.
For the “No Touch Function On the Whole Touch Screen” problem, performing a swapping test is very helpful. For example, you can use an alternate controller to test the original touch screen. If it’s OK, the problem most likely lies with the original controller. If it’s still NG, you can use an alternate touch screen to test. If the new touch screen resolves the problem, you can disassemble the original one and assemble the new touch screen onto the touch monitor. If changing both the touch screen and controller does not help to solve the problem, you can check the cables and wire board although the chance of these being the root of the problem is relatively minor.
2. Dead Zone In Partial Area of The Touch Screen
If the dead zone is in the middle of the touch screen, the problem is always caused by dust or stains accumulating on the edges of the touch screen or on the reflection stripes of the touch screen. For this kind of dead zone, the controller LED will not brighten when you touch the screen in the dead zone. The solution is to remove the front bezel and clean the touch screen and inside surface of the front bezel with alcohol and soft cloth. In the meantime, please pay attention to the dust-proof strips stuck onto the inside surface of the front bezel. Where there is a defective dust-proof strip, there would also be some gummy depositing onto the touch screen, which is the root cause of the dead zone. For such situations, the defective dust-proof strips must be replaced.
If the dead zone is on the edges and the controller LED does not brighten when you touch the screen in the dead zone, the solution is the same as above.
If the dead zone is on the edges but the controller LED brightens when you touch the screen in the dead zone, the problem most likely lies with the calibration. If this is the case, please kindly go into the touch driver control panel and re-calibrate the touch screen carefully.

3. Low Sensitivity
You can adjust the sensitivity level in the touch driver control panel. Level 4 is the recommended level.

4. Drifting
If the cursor always goes to the positions which are different from the points touched, it is known as a drifting problem. There are two kinds of drifting phenomena, as stated below:
1) If the drifting of the cursor is regular, this kind of problem can be solved by calibration.
2) If the drifting of the cursor is irregular, it seems that there is some interference around the touch system. Please try to adjust the sensitivity level to a lower one to solve such a problem.

5. Touch Screen Care and Cleaning
The touch screen requires very little maintenance. General Touch recommends that you periodically clean the touch screen surface. Typically, an isopropyl alcohol and water solution ratio of 50:50 is the best cleaning agent for the touch screen. You can also use straight isopropyl alcohol or any other neutral proprietary glass cleaner. Using a non-neutral cleaner may corrode the surface layer with special treatment and consequently cause it to lose the ability to perform its function. If the cleaner enters into the area containing the reflection stripes, they may be corroded and ultimately the touch function will be affected.
Please apply the cleaner with a soft, lint free cloth. Always dampen the cloth and then clean the screen. Be sure to spray the cleaner onto the cloth, not the screen. This method is helpful in controlling the cleaner consumption. If the cleaner is sprayed onto the touch screen directly, it is easy to spray too much cleaner, and then the cleaner, combined with dust and dirt, will seep into the area containing the reflection stripes through the gap between the front bezel and the touch screen, and therefore will affect the touch function.

  Failure in the Display System
Failure Description:
1. Color Distortion
Step-1: To judge whether the color distortion is partial to certain areas or the whole display area. If the color distortion happens in the whole display area, please go into the OSD menu and “Auto Color” the touch monitor, and then the problem may be solved. If the color distortion remains, either affecting the whole screen or only certain areas, please go to Step-2;
Step-2: please Use another VGA cable and see whether the problem still persists. If it does, please go to Step-3;
Step-3: please change the A/D Board of the touch monitor and see whether the problem still persists. If it does, please go to Step-4;
Step-4: please change the LVDS cable of the touch monitor and see whether the problem still persists. If it does, the problem most likely stems from a fault in the LCD Panel.
Step-5: Change the LCD Panel.

2. Black lines
Step-1: Determine the root cause of the black lines. There are two kinds of black lines, as stated below:
1) The black line is akin to a dark lane. In the dark lane, the color of the picture is normal but only the brightness is much lower. For this kind of black lines, the problem could stem from the failed CCFL. please go to Step-3;
2) The black line is akin to a really black lane, it cannot show pixels of other colors, so the line is always black. This kind of problem may stem from the A/D Board, the LVDS cable or the LCD Panel. If this is the case, please go to Step-2;
Step-2: please change the A/D Board and the LVDS cable of the touch monitor to see whether the problem still persists. If it does, the problem most likely stems from a fault in the LCD Panel.
Step-3: Change the LCD Panel

3. LCD with color spots
Step-1: Determine the root cause of the color spots. There are several kinds of color spots, as shown below:
1) The color spots are flickering as if affected by a degree of interference. For this kind of color spots, the problem may lie with the A/D Board, the LVDS cable or the video card of the PC. For this problem, please go to Step-2;
2) The quantity of light dots/ dark dots/the sum total of light dots and dark dots should be within the bounds of the General Touch outgoing specification. If the quantity of light dots/ dark dots/ dead dots//the sum total of light dots and dark dots is more than that specified by the General Touch outgoing specification, you can apply to change LCD Panel within the warranty period. If the color spots don’t affect normal usage, we suggest that it is not necessary to change the LCD Panel. (Explanation: The definition of a light dot: In a black picture, a white dot is a light dot. The definition of a dark dot: In a white picture, a black dot is a dark dot.)
Step-2: please change the A/D Board and the LVDS cable to see whether the problem still persists. If it does, the problem probably stems from the video card.
Step-3: Use a different video card to test the problem.

4. Fail Lamps
please change the A/D Board and the LVDS cable of the touch monitor to see whether the problem still persists. If it does, the problem probably stems from the LCD Panel.
Step-1:please change the A/D Board and the LVDS cable of the touch monitor to see whether the problem still persists. If it does, the problem probably stems from the LCD Panel.
Step-2: Change the LCD Panel

5. Black Screen
Firstly, we need to check the status of the LED on the OSD board. There are three different kinds of status, as stated below:
1) If the LED is green, it indicates that there is a VGA or DVI signal, and that the A/D board is OK. The problem would therefore lie with one of the Inverter Board, the LVDS cable or the LCD Panel. In this situation, please follow the below instructions:
Step-1: please change the Inverter Board of the touch monitor to see whether the problem still persists. If it does, please go to Step-2;
Step-2: please change the LVDS cable to see whether the problem still persists. If it does, the problem probably stems from the LCD Panel.
Step-3: Change the LCD Panel.
2) An orange or red LED indicates that there is no video input signal. The problem may lie with either the VGA or the DVI connection. Please try to turn the touch monitor off and on via the OSD key to see whether the problem still persists.. Using an alternate VGA or DVI cable will be helpful too.
3) If the LED is dim, it indicates either that the power supply of the A/D board is off, or that the A/D Board has failed. Please try to turn the touch monitor on and off via the OSD key to see whether the problem still persists. If it does, please change to another A/D board.
Another solution is to check whether there is either a General Touch logo or "No Signal" is shown when restarting the touch monitor. If the General Touch logo is not shown, the A/D board may be defective. If “No Signal” is shown, there is likely to be a failure with either the VGA or the DVI connections.

Failure Description: Fail PCB
After performing a swapping test, if you can confirm that the problem is from a PCB, changing to new PCB is the optimal solution. Please tell us the model name of the PCB which is marked on the PCB and then we will prepare the new PCB for you.