PC Repair and Maintenance: A Practical Guide (Charles River Media Networking/Security)

Input devices are devices that allow the user to input data into a computer. The most obvious input devices are pointing devices (mice and their equivalents) and keyboards. Other input devices include such things as microphones used in the case of voice recognition systems. This chapter is limited to discussion of keyboards and common pointing devices.

Pointing Devices

The most common pointing device is the mouse. Others include the trackball, touchpad, and track stick ("pencil eraser") controls found on some laptops. All but the last one come in different forms.

Pointing Device Types

Pointing devices can be divided into interface type, features, and detection system.

Mouse Interfaces

Mice can be connected to PCs in at least one of four ways: serial (DB-9 female connector), PS/2 (the small, round, 5-pin connector), USB, and infrared or radio frequency wireless. Many mice come with adapters so that an individual mouse can be used in both PS/2 and serial ports, or both PS/2 and USB ports. More information about these follows:

Serial: This is the original interface used in personal computers. Serial devices are hot-pluggable. Although new computers no longer come with serial mice, the vast majority of computers have serial ports, so a serial mouse is the perfect choice when the built-in PS/2 port fails. In fact, serial mice used to come with drivers on floppy disks, although Windows 95 and later have the drivers.

PS/2: This is the standard mouse interface for the vast majority of computers with ATX and similar motherboards. These computers have dedicated PS/2 mouse ports that can be used only for PS/2 pointing devices and those adapted to PS/2. These devices are not hot-pluggable; plug in and remove only with the computer's power off. There is no guarantee that ignoring this warning will fry the motherboard, but it is not worth the risk. Windows installs PS/2 mice transparently to the user unless the device has unusual features, in which case, a software disk might be needed.

USB: This is the standard mouse port for many new computers. However, because most computers still have PS/2 mouse ports, unless the mouse you want is available only in USB, it is a good idea to use a PS/2 mouse. This is because there are many devices that use USB ports, but only one that can use a PS/2 mouse port, so you might as well save the USB port for some other device. Most of the feature-laden mice use USB. USB devices are recognized and installed by Windows, and many come with software disks. Windows, however, has drivers for almost all commercially available mice. USB mice are also good choices for replacements when PS/2 ports fail.

Wireless: Wireless mice use one of the other interfaces in this list. They come in two varieties, infrared and radio frequency (RF). The RF types are usually preferred because the receiver and mouse do not have to be directly in line of site of each other. The mouse runs on battery power, so plan to have spare batteries on hand or at least hold on to a basic wired mouse in case of an emergency.

Detection Types

Mice come in two detection types: mechanical (ball) and optical. Ball mice have rubber-coated metal balls that roll over a surface. This is the cheapest and most common type. It is also the most troublesome because the mechanical parts get clogged with dust, lint, and hair, and they also break. They usually need mouse pads, or at least table or desktops of a certain texture to work well.

Optical mice use a reflected red LED light to detect movement. Early optical mice sometimes required certain types of surfaces, but since then, optical mice have become easy to use and much more reliable than ball mice.

Mouse Features

The most common feature is a scroll wheel. This allows the up-and-down scrolling of a window by turning the wheel with your thumb, rather than clicking on the scroll arrows or moving the scroll bars on the screen. The next most common feature is an ergonomic shape.

Non-Mouse Pointing Devices

Trackpads, touchpads, and track sticks are the most common. The track sticks are found in the center of laptop keyboards. Touchpads are commonly found on laptops, although they are also available built into separate keyboards, or as freestanding devices. Trackballs can also be found in any of those locations. These devices, shown with others in Figure 9.1, are often very helpful for people who experience wrist pain from excessive use of mice.

Figure 9.1: Pointing device assortment.

Touchpads have no moving parts, so they tend to be very reliable. The most common manufacturers of touchpads are Synaptics (synaptics.com) and Alps (alps.com). Free software available from the manufacturers or the computer maker provide touchpad users with many features such as scrolling, tapping for left-clicks, and click-and-drag operations with one finger (not requiring the use of the mechanical mouse button).

Pointing Device Configuration

Although there is considerable configuration possible in the Control Panel Mouse applet, most settings are typically left at their defaults. Microsoft has done a good job of setting these defaults. It is helpful to be familiar with these settings so that you aren't bewildered when you encounter unusual pointing device behavior. This applet looks like the one in Figure 9.2 unless extra pointing device software is installed.

Figure 9.2: A typical Mouse applet from Windows Me.

The most useful settings in this applet include double-click speed, which is useful for older people and others who have trouble double-clicking. There is also a setting for right- and left-handers that reverses the functions of the left and right mouse buttons. There is a whole host of settings of pointer appearance and speed. Windows Me and XP come with a check box that causes a circle to appear around the pointer when the Ctrl key is pressed, although it doesn't always work in Windows Me. There is also a Click Lock setting that allows clicking and dragging without holding down the button. Another setting is in more than one place in some versions of Windows: single- or double-click to open an item is both in the Mouse applet and in the Tools > Folder Options command in any Windows Window.

Removal and Installation of Pointing Devices

As covered earlier in this chapter, removal and installation of these devices isn't complicated unless you are trying to replace a pointing device that is built into a laptop, a repair that is beyond the scope of this book. The main point to remember is never to plug in or unplug a PS/2 device with the computer powered on. Other points to remember are:

• Don't reverse pointing device and keyboard PS/2 connections. This will cause neither device to work, and you'll have to shut off the power without a proper shutdown to switch the connectors. You might see badly labeled connections, such as the one shown in Figure 9.3. In this case, the keyboard port is on the bottom and the mouse port is on the top.

• USB devices are hot-pluggable and are recognized as new hardware.

• Serial mice can be safely plugged in or removed while the computer is running.

  Figure 9.3: Badly labeled PS/2 ports.

Diagnosing Pointing Device Problems

Pointing devices are not the culprit in most computer problems, but because they are almost indispensable, the problems they do have are important to repair quickly.

Error Messages

There is only one common error message related to pointing devices, a message indicating that Windows didn't detect a mouse. The message is accompanied by a note that a serial mouse can be attached right away, but that to install a PS/2 mouse, you'll have to shut down the machine. If there actually is no mouse connected, the solution is obvious. If a PS/2 mouse is connected, the first thing to check is that the mouse and keyboard connectors aren't reversed. Again, switch them only once the computer has been shut down. If the pointing device is installed correctly, however, there is a problem. The pointing device could be dead, so swapping a known good device should confirm that. For this reason, it is a good idea to keep various types of mice around any computer shop. If a known good mouse doesn't work either, then the problem could be in the port. First, check the BIOS setup program to make sure that the port in question hasn't been disabled. Then, unless the port is PS/2, check in Device Manager for the same thing. If the port is disabled or not installed in Device Manager, attempt to enable it or reinstall it. If you still can't get it to work, the port might be disconnected or broken. In an older computer, the serial port might not be part of the motherboard. The cable from the port to the header connector on the motherboard might be detached, damaged, or connected to the wrong header connector. Of course, these possibilities are unlikely unless someone opened the case and made changes. If the port cannot be fixed, the simplest solution is to use a pointing device with a different interface. In an AT computer that accepts only serial pointing devices, you can try a different serial port, if there is one available. If not, you might be able to replace the port or add a new one. Search the Web for these replacement parts if you don't have old ones available. But remember, AT computers are probably not worth the time involved to fix.

Jerky Pointer

There are two possibilities for jerky pointers. One is a dirty or damaged mechanical ball mouse or trackball, and the other is that a computer's CPU and memory are being used heavily. The latter should be ruled out first. Often, use of memory- or processor-intensive hardware such as printers, scanners, or optical disc burners cause the pointer to be jerky. There are several ways to determine if this is the case. First, a damaged or dirty mouse will not spontaneously start working normally; if it does, the problem is probably not in the device. Another way to tell is if the computer reacts slowly or erratically to everything you try. For example, if you press the Windows key (shown in Figure 9.5, appearing in the section on keyboards) or click Start, but the Start menu takes a noticeable amount of time to appear, the problem is probably not related to the mouse. In 2000 and XP, you can check Windows performance in Task Manager; look for a high percentage of CPU time being used. In 9x, look at the Performance tab of the System applet for the percentage or resources remaining. If the number is low, something might be draining resources. Sometimes, Windows will run poorly for no apparent reason.

If everything appears to be working normally, except for a jerky pointer, and the pointing device is a ball mouse or trackball, try cleaning the device. It is probably a good idea to save your open files and close all programs to avoid clicking anything that can cause problems. You could also clean the device while the computer is shut down.

To clean a ball mouse, twist and remove the bottom plate in the direction of the arrow as shown in Figure 9.4. Remove the ball. You will probably find grit and stringy substances around the rollers. Pull out this debris. Air spray such as Blow Off can be helpful. Replace the ball and plate and try the mouse again. If this doesn't help, try a new or known good mouse. If the new mouse solves the problem after a cleaned old mouse is still jerky, discard the old mouse. If the new mouse doesn't solve the problem, you'll have to go back to the drawing board. It will be helpful to try both mice in a different computer. Make sure to note which mouse is which; if necessary, mark the bottom of the old mouse with a permanent marker.

Figure 9.4: Opening the bottom of a ball mouse.

Similar problems will occur in mechanical trackball-style pointing devices. The balls can be removed by pulling them out, or by pushing from a hole in the bottom. Use an air spray and blow out the dust.

Of course, to avoid the problem of contaminated mice, recommend an optical mouse or touchpad to the user.

Lockups

Lockups are when the computer stops responding to any input. The mouse pointer freezes, keyboard commands are ignored, and the screen doesn't change. The telltale sign of a lockup is when the Num Lock light on the keyboard (if there is one) doesn't change when the <Num Lock> key is pressed. However, because the most obvious sign of a lockup is the frozen pointer, many users are convinced that the problem is in the mouse. Many mice are sold to consumers who want to repair a lockup. In fact, a bad mouse can lose the capability to move the pointer, but the screen will still change and keyboard commands will still be accepted. However, lockups are much more common culprits of frozen pointers. We discuss lockups in more detail in Chapter 11, "Troubleshooting."

The Center Mouse Button

You have most probably noticed that some mice have three buttons. Software that comes with the mouse can be used to configure the center button for a number of different functions such as the Enter key. Most people didn't program these, so this type of mouse never really caught on.