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OBJECTIVES. 1. Describe the characteristics of a good work space. 2. Outline steps for using a digital multimeter to perform voltage, resistance, and current checks on a system, as well as identify common DMM tests associated with personal computers.
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OBJECTIVES 1. Describe the characteristics of a good work space. 2. Outline steps for using a digital multimeter to perform voltage, resistance, and current checks on a system, as well as identify common DMM tests associated with personal computers. 3. List preliminary steps for diagnosing computer problems. 4. Perform visual inspections of a system. 5. Describe the three general categories of problems into which symptoms can be grouped, and differentiate between them. 6. Differentiate between software- and hardware-based troubleshooting techniques. 7. Use disk-based diagnostic tools to isolate system problems. 8. Describe the function of a POST card. 9. Describe quick checks that can be used to determine the nature of system hardware problems. 10. Describe FRU-level troubleshooting. 11. Describe the steps for isolating power supply problems. 12. Outline checks to isolate problems that produce a dead system. 13. Discuss methods of dealing with symptoms that are not defined well enough to point to a particular component.
Identify basic troubleshooting procedures and good practices for eliciting problem symptoms from customers: Troubleshooting/isolation/problem determination Determine whether a problem is a hardware or software problem
Gather information from user regarding: Customer environment Symptoms/Error codes Situation when the problem occurred
The following list identifies some of the organizational aids you need: A parts organizer to keep track of small parts such as screws and connectors you may remove from the device. This organizer need not be extravagant. A handful of paper cups or clear plastic sandwich bags will do nicely. A small note pad or notebook to keep track of your assembly/troubleshooting steps.
The following list identifies some of the organizational aids you need: (continued) A roll of athletic or masking tape. You can use the tape to make tags and labels to help identify parts, where they go, and how they are connected in the circuit. Take the time to write notes and stick them on your parts organizers, circuit boards, and cables you remove from the system, and so forth.
WARNING Setting the meter—It is normal practice to first set the meter to its highest voltage range to make certain that the voltage level being measured does not damage the meter.
WARNING Power off—Unlike the voltage check, resistance checks are always made with power removed from the system.
TEST TIP Know what readings to expect from a multimeter when testing fuses, speakers, and typical power-supply voltages in a PC.
Careful observation—The most important thing to do when checking a malfunctioning device is to be observant. Begin by talking to the person who reported the problem. You can obtain many clues from this person. Careful listening also is a good way to eliminate the user as a possible cause of the problems. Part of the technician’s job is to determine whether the user could be the source of the problem—either trying to do things with the system that it cannot do, or not understanding how some part of it is supposed to work.
TEST TIP Be well aware that the user is one of the most common sources of PC problems. In most situations, your first troubleshooting step should be to talk to the user.
Error message formats—Whenever a self-test failure or setup mismatch is encountered, the BIOS may indicate the error through a blank screen, or a visual error message on the video display, or an audio response (beep codes) produced by the system’s speaker.
Check the outside—Check all externally accessible switch settings.
Documenting things—Take time to document the problem, including all of the tests you perform and their outcomes. Your memory is never as good as you think it is, especially in stressful situations such as with a down computer. This recorded information can prevent you from making repetitive steps that waste time and may cause confusion. This information also proves very helpful when you move on to more detailed tests or measurements. Also, label all cables and connectors prior to removing them. This will assist you in reconnecting things as you progress through the troubleshooting process.
Observing bootup—Carefully observing the steps of a bootup procedure can reveal a great deal about the nature of problems in a system. Faulty areas can be included or excluded from possible causes of errors during the bootup process.
The observable actions of a working system’s cold-boot procedure are listed as follows, in their order of occurrence: 1 When power is applied, the power supply fan activates. 2 The keyboard lights flash as the rest of the system components are being reset. 3 A BIOS message displays on the monitor. 4 A memory test flickers on the monitor. 5 The floppy disk drive access light comes on briefly (if enabled in the CMOS bootup sequence.)
The observable actions of a working system’s cold-boot procedure are listed as follows, in their order of occurrence: (continued) 6 The hard disk drive access light comes on briefly. 7 The system beeps, indicating that it has completed it power on self tests and initialization process. 8 The floppy disk drive access light comes on briefly before switching to the hard drive. At this point in the process, the BIOS is looking for additional instructions (boot information), first from the floppy drive and then from the hard drive (assuming that the CMOS setup is configured for this sequence).
The observable actions of a working system’s cold-boot procedure are listed as follows, in their order of occurrence: (continued) 9 For Windows machines, the “Starting Windows message” appears on the screen.
TEST TIP Memorize the order of the series of observable events that occur during the normal (DOS) boot up.
You can still group errors that occur before the beep into two distinct categories: Configuration errors Hardware failures
Configuration problems—You can trace the majority of all problems that occur in computer systems back to configuration settings.
It is usually necessary to run the system’s CMOS setup utility in the following three situations: 1 The first situation occurs when the system is first constructed. 2 The second occurrence happens if it becomes necessary to replace the CMOS backup battery on the system board. 3 Whenever a new or different option is added to the system (such as a hard drive, floppy drive, or video display), it may be necessary to run the Setup utility (although see the note “CMOS Setup Utility and Plug-and-Play”).
CMOS Setup Utility and Plug-and-Play—In most newer systems, the BIOS and operating system use Plug-and-Play (PnP) techniques to detect new hardware that has been installed in the system. These components work together with the device to allocate system resources for the device. In some situations, the PnP logic will not be able to resolve all the system’s resource needs and a configuration error will occur. In these cases, the user must manually resolve the configuration problem.
TEST TIP Know the situations that cause a Press F1 to Continue error message to display.
Errors that occur between the beep and the presentation of the operating system’s user interface (command prompt or GUI) generally have three possible sources: Hardware failure (physical problem with the boot drive) Corrupted or missing boot files Corrupted or missing operating system files
Ground yourself—Because there may be Metal Oxide Semiconductor (MOS) devices on the board, you want to ground yourself before performing this test. You can do so by touching an exposed portion of the unit’s chassis, such as the top of the power supply.
Field-Replaceable Units (FRUs) are the portions of the system that you can conveniently replace in the field.
TEST TIP Know which devices in a typical PC system are FRU devices.
Exchanging FRU components—Once a hardware error has been indicated, start troubleshooting the problem by exchanging components (cards, drives, etc.) with known good ones.
Write it down—Make certain to take the time to document the symptoms associated with the problem, including all of the tests you make, and any changes that occur during the tests. This information can keep you from making repetitive steps.
Work backwards—Once you have isolated the problem, and the computer boots up and runs correctly, work backwards through the troubleshooting routines, reinstalling any original boards and other components removed during the troubleshooting process.
Error messages typically associated with configuration problems include the following: CMOS Display Type Mismatch CMOS Memory Size Mismatch CMOS Battery State Low CMOS Checksum Failure CMOS System Options Not Set CMOS Time and Date Not Set
Typical error messages associated with boot-up problems include the following: General Failure Error Reading Drive x Bad or Missing Command Interpreter Non-System Disk or Disk Error Bad File Allocation Table
Identify common symptoms and problems asso-ciated with each module and how to troubleshoot and isolate the problems. Contents may include: Mouse Parallel ports Hard drives Power supply Motherboards Modems BIOS USB CMOS Slot covers Floppy drive failures Sound card/audio Processor/Memory symptoms Monitor/Video Large LBA, LBA POST audible/visual error codes Troubleshooting tools (for example, multimeter)
Typical symptoms associated with power-supply failures include: No indicator lights visible, with no disk drive action, and no display on the screen. Nothing works, and the system is dead. The ON/OFF indicator lights are visible, but there is no disk drive action and no display on the monitor screen. The system fan may or may not run. The system produces a continuous beep tone.
Special consideration must be taken when a system is inoperable. In a totally inoperable system, there are no symptoms to give clues where to begin the isolation process. In addition, it is impossible to use troubleshooting software or other system aids to help isolate the problem.
