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Troubleshooting Essential Hardware. Chapter 3. Overview. In this chapter, you will learn how to Troubleshoot CPUs Troubleshoot RAM Troubleshoot BIOS and motherboards Troubleshoot power supplies. Troubleshooting CPUs. Troubleshooting CPUs.
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Troubleshooting Essential Hardware Chapter 3
Overview In this chapter, you will learn how to Troubleshoot CPUs Troubleshoot RAM Troubleshoot BIOS and motherboards Troubleshoot power supplies
Troubleshooting CPUs • Overheating—can cause system to not start or to lock up. Newer CPUs will usually shut themselves down before overheating. • Too much heat dope (thermal paste) can impede the flow of heat from the CPU to the heat sink and cause the CPU to heat up rapidly. • Not enough thermal paste can cause the CPU to heat up and shut down. • Faulty fan power connection can cause the CPU to heat up and shut down. • Heating may take longer and cause problems after boot and OS load
Troubleshooting CPUs (continued) • Environmental heat/lack of adequate ventilation can cause CPU heat-up and shutdown • Catastrophic failure • May cause Windows Stop error (Blue Screen of Death) • May cause PC to shut down or go black • May burn up components
Troubleshooting CPUs (continued) Figure 1: Blue Screen of Death
Memory Errors • Memory errors can include • Parity errors • ECC error messages • System lockups • Page faults • Other error screens in Windows
Memory Errors (continued) • Write down memory error addresses. • If the error returns with the same address each time, it is likely a RAM stick failure. • If the error address changes, it is likely not a RAM failure. • System lockups and page faults often indicate RAM problem. • RAM and parity errors can trigger a non-maskable interrupt (NMI) that results in the Blue Screen of Death (BSoD).
Memory Errors (continued) Figure 2: Windows error message
Memory Errors (continued) • Not all intermittent errors are caused by bad RAM • Dying power supply, electrical interference, and buggy applications or hardware can also produce intermittent errors.
Testing RAM • Several RAM testing devices are available, but many are expensive. • Can replace one stick at a time until problems disappear. • Use a software-based tester such as Memtest86. • Windows 7 includes the Memory Diagnostics Tool, which can automatically scan your computer’s RAM when you encounter a problem.
Testing RAM (continued) Figure 3: Memtest86 in action
ROM Initiates the POST Process • Upon boot, the ROM initiates the POST process. • The POST routine sends out a message to all assumed components to initiate self-tests. • This determines whether the components are working properly. The quality of POST diagnostics is determined by the component. • If a component fails self-diagnostics, the POST process halts and sends an error message.
Beep Codes • Before and during the video test: beep codes • If video is missing or faulty, you’ll hear one long beep followed by three short beeps. • If RAM is missing or faulty, you’ll hear a rather alarming beeping/buzzing that will repeat as long as the computer is on. • If the POST completes successfully, you’ll hear one or two short beeps.
Text Errors • Once the video is determined to be good, errors can be displayed. • Errors are usually displayed in clear text, though they can sometimes be rather cryptic. Figure 4: POST text error messages
POST Cards • The small expansion card installs into an available slot • Used to monitor the POST and identify whether a piece of hardware is causing startup issues • Note the light-emitting diode (LED) display to see what device POST is currently checking • Refer to the two-digit hex code on the LED display to determine the faulty POST code • Look up the code in the companion manual—it can help identify the faulty component
POST Cards (continued) • If the PC passes POST, the problem is more likely a software problem • POST cards used to be an essential tool for techs • Today they are rarely used, and then only on a “dead” PC to determine at which level it’s dead • If the POST card shows no reading, the problem is before the POST and must be related to the CPU
POST Cards (continued) Figure 5: POST card in action
The Boot Process • The power supply checks for proper voltage. • If the proper voltage is found, the power supply sends a signal through the power-good wire. • This awakens the CPU, which in turn sends a built-in memory address, which is the first line of the POST program on the system ROM. • The ROM begins the POST routines. • Once the POST is passed, the ROM begins the boot process (the bootstrap loader) by looking for an operating system according to the CMOS settings.
The Boot Process (continued) Figure 6: CMOS boot order
The Boot Process (continued) • The CMOS settings tell it which device to try to boot from. • It looks at the boot sector of that device (floppy, CD-ROM, hard drive, etc.) and tries to load an operating system. • Once the boot process begins, control is handed over to the operating system. • Some BIOSs allow the PC to use a preboot execution environment (PXE). • A PXE enables you to boot a PC without any local storage by retrieving an OS from a server over a network.
Losing CMOS Settings • The battery provides continuous trickle charge to hold data. It also keeps the clock running. • If the battery dies or is removed, all data is lost and the system returns to factory defaults. • Common errors • CMOS configuration mismatch • CMOS date/time not set • No boot device available • CMOS battery state low
Losing CMOS Settings (continued) • Common reasons for losing CMOS data • Pulling and inserting cards • Touching the motherboard • Dropping something on the motherboard • Dirt on the motherboard • Faulty power supplies • Electrical surges • If settings keep resetting, replace the battery.
Losing CMOS Settings (continued) Figure 7: A CMOS battery
Flashing ROM • Flash ROM chips can be reprogrammed. • Download the program from the manufacturer and follow the instructions. • Typically insert a removable disk of some sort (usually a USB thumb drive) containing an updated BIOS file. • Only flash the BIOS if necessary.
Flashing ROM (continued) Figure 8: ROM-updating program for an ASUS motherboard
Troubleshooting Symptoms Catastrophic failure System will not boot. Although uncommon, most motherboards will fail (if they’re going to) within the first 30 days due to manufacturing defects, called burn-in failure. Electrostatic discharge is the other most common cause. To fix, replace the motherboard.
More Troubleshooting Symptoms Component failure Intermittent problems Examples include a hard drive that shows up in CMOS but not in Windows Most common causes are electrical surges and ESD Sometimes a BIOS upgrade may solve this problem if the issue is lack of BIOS support for a newer technology Fixes include replacing the component with an add-on card or flashing the BIOS
More Troubleshooting Symptoms (continued) Ethereal symptoms Things just don’t work all the time. PC reboots itself for no apparent reason. Blue Screens of Death appear as the computer crashes. Causes include faulty components, buggy device drivers or application software, slight corruption of the operating system, and power supply problems. Fixes include flashing the BIOS or replacing the motherboard.
Techniques Isolate the problem by eliminating potential factors. Check, replace, verify good component. If the hard drive doesn’t work, try a different hard drive, or try the same hard drive with a different motherboard. If the new hard drive works, you know it wasn’t the motherboard. If the same hard drive with a different motherboard works, you can suspect the motherboard.
Options There are a couple of options for dealing with a motherboard failure. Catastrophic failure: replace the motherboard. Component failure: consider an add-on card to replace the device. Consider a BIOS update if the device issue is a problem other than physical damage. Figure 9: Adaptec PCIe SATA card
Troubleshooting Power Supplies Power supplies fail in two ways Sudden death When the fan doesn’t turn and no voltage is present Computer simply stops working Slowly over time Intermittent errors Output voltages may exceed specs (±10%)
Lab – Power Supply Test Set the multimeter to test DC. Turn on the PC. Put the black lead onto any black wire connection. Put the red lead onto a colored wire. Figure 10: Testing one of the 5-V DC connections • 12 V ± 10 percent • 10.8 to 13.2 V • If readings are outside tolerance and symptoms exist, replace power supply. • 5V ± 10 percent • 4.5 to 5.5 V • 3.3 V ± 10 percent • 2.97 to 3.63 V
Power Supply Test Power supplies need a load Plug into motherboard Plug into tester Check power switches If faulty, can turn onwith motherboard jumper Figure 11: ATX power supply tester
When Power Supplies Die Slowly Intermittent problems Sometimes occur, sometimes don’t You could measure voltage now and it’s good; ten minutes later, system crashes A dying power supply can cause Random lockups and reboots Sporadic boot-up difficulties When you encounter intermittent symptoms, consider replacing the power supply
Fuses and Fire Circuit breakers are heat-sensitive Sense when amperage exceeds threshold Breaks the circuit to stop flow of electricity Fuses blow for a reason Power supply is malfunctioning As a designed safety precaution, fuses blow (break) to stop circuit Alternative is a possible fire
Fire Extinguishers Class A Ordinary combustibles such as paper and wood Class B Flammable liquids such as gasoline Class C Live electrical equipment Use only Class C extinguishers on electrical fires
