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The touch screen is a device that integrates display and touch control. Because the touch system serves as a bridge for human-computer interaction and is widely contacted by humans, and since it is primarily made of glass, it is relatively fragile, resulting in a higher failure and breakage rate compared to other devices. Therefore, touch screen repair has formed an industry.
1. Touch Screen Inaccuracy
1. Fault Phenomenon
A surface acoustic wave touch screen cannot complete the corresponding operation when touching the display screen with a finger.
2. Fault Analysis and Handling
This phenomenon may be due to dust covering the reflection stripes around the screen after a period of use. Wipe it with a dry soft cloth, then power off, restart the computer, and recalibrate. It is also possible that the reflection stripes of the acoustic screen are slightly damaged; in this case, it cannot be fully repaired.
If it is a capacitive touch screen, the screen calibration program can be run in the following situations: (Start — Programs — Microtouch Touchware)
1) After the driver software is installed for the first time.
2) Every time the display resolution or display mode is changed.
3) Every time the display area is changed.
4) Every time the controller frequency is adjusted.
5) Every time the cursor does not correspond to the touch point.
After calibration, the calibration data is stored in the controller’s register, so there is no need to recalibrate the screen after each system startup.
2. Touch Screen Not Responding
1. Fault Phenomenon
A touch screen does not work, and there is no response when touching any part.
2. Fault Analysis and Handling
First, check if the wiring interfaces are loose, then check if there are conflicts in the serial port and interrupt number. If there are conflicts, adjust the resources to avoid them. Also, check if there are cracks on the surface of the touch screen; if there are, replace it in time. Additionally, check if there is dirt on the surface of the touch screen; if so, clean it with a soft cloth. Observe if the indicator light on the control box is working normally; when normal, the indicator light should be green and flashing.
If all the above parts are normal, you can use the substitution method to check the touch screen, first replace the control box, then replace the touch screen, and finally replace the host.
If it is a surface acoustic wave touch screen, the following repairs can be conducted:
1) It may be that one of the wires connecting the host keyboard port (taking 5 volts for the touch screen working voltage from the keyboard port) is not connected; please check the wiring.
2) It may be that the serial port number selected during the installation of the touch screen driver does not correspond to the actual serial port number the touch screen is connected to; please uninstall the driver and reinstall it.
3) It may be that the host is a domestic original machine, and the installed operating system is an OEM version, which has been adjusted by the manufacturer, causing non-standard serial communication that is incompatible with the touch screen driver. If feasible, format the hard disk and install the system after the touch screen driver.
4) It may be that the version of the touch screen driver is too low; please install the latest driver.
5) Check if there are devices in the host that conflict with the serial port resources. For example, some network cards default to IRQ 3 after installation, which conflicts with IRQ of COM2; at this time, the IRQ of the network card should be changed to an unused IRQ.
1) Check if the wiring of the touch screen is connected correctly; ensure the connection from the keyboard port to the host (taking 5 volts for the touch screen working voltage) is intact.
2) Observe the status of the indicator light on the touch screen control box; if it is not lit or shows a red light, it indicates that the control box is faulty and should be replaced.
3) If the above conditions are not confirmed, please delete the touch screen driver and restart the computer to reinstall the driver, or replace it with a higher version of the driver.
4) Check if there are devices in the host that conflict with the serial port resources. For example, some network cards default to IRQ 3 after installation, which conflicts with IRQ of COM2; at this time, the IRQ of the network card should be changed to an unused IRQ. It is possible that the computer motherboard and the touch screen control box are incompatible; please replace the host or motherboard.
5) If the touch screen has been used for a long time (3-4 years) and some areas cannot be touched, it may be that the touch screen is damaged; please replace the touch screen.
If it is a capacitive touch screen, the following repairs can be conducted:
1) Check if the wiring of the touch screen is connected correctly; if it is an external control card, the control box part connects directly to the cable extending from the touch screen. The power part connects through a keyboard converter (the small rubber head beside the RS232 connector must be removed first to insert the power line), one end connects to the keyboard port of the host, and the other end connects to the computer keyboard. Insert one end of the 5V power supply into the connection of the 232 port and insert the RS232 connector extending from the control box into the 9-pin hole of the host. If your host uses a 25-pin port, please buy a 9-25 adapter for conversion. If your host’s keyboard port is the original small keyboard port, please buy a pair of adapters from large keyboard to small keyboard.
2) If it is an internal card type, check if the jumpers are set correctly according to the control card’s jumper instructions. Since the configurations of user machines vary, and the external devices used are also different, to avoid conflicts with the touch screen and user peripherals, Micro Touch provides jumper instructions for the control card for customer selection.
3. Long Touch Screen Response Time
1. Fault Phenomenon
A touch screen requires a long time to respond after touching the display screen with a finger.
2. Fault Analysis and Handling
This may be due to moving water droplets sticking to the touch screen; simply wipe it with a dry soft cloth. It may also be that the host is of too low a grade, such as having a low clock frequency; in this case, it is best to replace the host.
4. Partial Touch Screen Not Responding
1. Fault Phenomenon
A touch screen does not respond in some areas when touched with a finger.
2. Fault Analysis and Handling
This may be due to the reflection stripes of the touch screen being partially covered; it can be cleaned with a dry soft cloth. It may also be that the reflection stripes of the touch screen are partially scraped off by a hard object, which cannot be repaired.
5. Touch Screen Normal but Computer Cannot Operate
1. Fault Phenomenon
A touch screen is tested to be normal, but the computer cannot operate when connected to the host.
2. Fault Analysis and Handling
This may be because the touch screen control card receives the operation signal before the host starts loading the touch screen driver; simply power off and restart the computer. It may also be that the version of the touch screen driver is too low; the latest driver needs to be installed.
6. Touch Screen Not Responding After Initial Startup Post Driver Installation
1. Fault Phenomenon
A touch screen does not respond after the driver is installed and it is started for the first time.
2. Fault Analysis and Handling
First, confirm whether the touch screen wiring connections are correct; if not, power off and correctly connect all lines. Then check if there are devices in the host that conflict with the serial port resources, checking and adjusting each hardware device, for example, some network cards default to IRQ 3 after installation, which conflicts with IRQ of COM2; at this time, the IRQ of the network card should be changed to an unused IRQ.
7. Touch Screen Unresponsive After Some Time of Use
1. Fault Phenomenon
A touch screen does not respond after being used normally for a period of time after startup.
2. Fault Analysis and Handling
1) Check in Windows 9x’s “Display Energy Settings” whether it is set to turn off the hard disk. The method is to right-click on the desktop, select the “Properties” command, then select the “Screen Saver” tab from the dialog box, click the “Settings” button, and set the parameters so that all except “Power Scheme” is set to “Always On”.
2) In some applications, due to poor grounding performance, the control box shell may be filled with static electricity, affecting the working electric field inside the control box, causing the touch to gradually fail. At this time, use a wire to ground the control box shell and restart.
3) Since surface acoustic wave touch screens are filled with sound waves on the surface when working, if the touch screen is not wiped for a long time, dust accumulation may block the reflection stripes, preventing the touch screen from working normally. For touch displays, gently wipe the dust around the reflection stripes through the gap between the display cover and the touch screen with a clean business card or paper bill, then restart the computer. For touch all-in-one machines, open the front cover of the display and wipe the dust around the reflection stripes with a clean towel, then restart the computer.
4) Many touch all-in-one machines use a method of taking power from the all-in-one machine’s power supply instead of the host, so check whether the 5V output of the all-in-one machine power supply is correct. Sometimes, if the instantaneous current is too large, the fuse may blow, in which case the fuse needs to be replaced.
8. Touch Screen Click Accuracy Decrease
1. Fault Phenomenon
A touch screen has decreased click accuracy, making it difficult to position the cursor.
2. Fault Analysis and Handling
1) Run the touch screen calibration program. (Start — Settings — Control Panel — Acoustic Screen — Calibrate Button).
2) If it is a newly purchased touch screen, try deleting the driver, then power off the host for 5 seconds and reboot to reinstall the driver.
3) If the above method does not work, it may be that the reflection stripes of the acoustic screen were slightly damaged during transport and cannot be fully repaired; you can calibrate by offsetting the calibration target in the opposite direction (relative to the direction away from the mouse).
4) If the acoustic screen becomes inaccurate after being used for a period of time, it may be that the reflection stripes around the screen or the transducer are covered with dust. If you are using a KA-type machine cabinet, you can open the top cover and use a dry soft cloth dipped in industrial alcohol or glass cleaner to clean its surface, then restart the system. Note that the transducers in the upper left, upper right, and lower right corners should not be damaged, then power off and restart the computer and recalibrate.
5) If there are water droplets or other soft substances sticking to the surface of the touch screen, the touch screen may misjudge the touch due to the presence of these substances; simply remove them.
9. Mouse Stays at One Point on Touch Screen
1. Fault Phenomenon
A touch screen has a mouse that cannot move after startup and stays at one point on the touch screen.
2. Fault Analysis and Handling
This situation occurs because the touch area of the resistive screen (the surface of the resistive screen is divided into touch and non-touch areas; clicking on the non-touch area has no response) is pressed by the display or cabinet shell, equivalent to being touched at a certain point continuously. If the cabinet shell presses the touch area, you can increase the distance between the cabinet and the display screen; if the display shell presses the touch area, you can try loosening the screws of the display shell a little to check.
10. Touch Screen Working Unstable
1. Fault Phenomenon
A touch screen works very unstably; sometimes it can click normally, and sometimes it has no response.
2. Fault Analysis and Handling
For this phenomenon, focus on checking if the wiring interfaces are loose, and whether there are conflicts in the serial port and interrupt numbers.
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