Chapter 15 PC Troubleshooting 643
Items to check:
Check the power supply for a power good signal. The power good signal is
sent back to the BIOS system to signal that the power supply is on and ready.
The signal back should be approximately 5 volts. Pin 1 is usually the power good
pin. Pull the connector back just far enough to check for 5 volts (+/–1 volt). If the
power is very low, there may not be sufficient voltage to power up the system.
The power output does not have to be completely dead to affect startup.
If the power good signal checks out, check the connection from the power
supply to the motherboard. Reseat this connection. Try reseating the CPU.
Sometimes the CPU is not making a good electrical contact. CPUs operate on
fairly low voltages. A slight oxidation buildup on one of the CPU’s pins that is
operating at 3.3 volts is sufficient to render the CPU dead. Cleaning the oxidation
will bring it back.
If you perform all of the listed operations and the system still fails to activate,
you probably have a defective motherboard.
Symptom 3:
The system tries to boot. There are two or more beeps, and then nothing (no
video). The fan is running, and there is a power light.
Items to check:
Make sure the monitor is plugged in correctly (both the data plug and the
power cord). Check the video card. Try reseating the card. If those actions do
not help, try to decode the beep error code. If you have the manual that came
with the motherboard, start there. Newer manuals are often CDs as opposed
to the traditional paper booklet. If there is no manual, look up the BIOS chip
manufacturer on the Internet. First, copy all information from the BIOS chip or
motherboard and then head to the manufacturer’s Web site.
Symptom 4:
You see a setup error indicated on the screen.
Items to check:
This is probably a CMOS setup problem. Access the BIOS setup routine by
using the key combination indicated on the screen. If no setup routine is given, try
key combinations you are familiar with. Some popular combinations can be found
in Figure 3-39 from Chapter 3—Motherboards. You can also look up the keystroke
combination for accessing the BIOS at the BIOS manufacturer’s Web site.
Normally, CMOS settings do not change. However, sometimes when you
install a new hard drive and the drive is automatically detected, the settings
change. Also, if the battery used to hold the CMOS data is going bad, you could
lose the settings. The date and time not matching the true date and time is a good
indication that your battery is going bad.
Be sure to write down the existing CMOS settings before you make any
changes to them. This is extremely important if you are going to try something
like the
Return to default settings
option. When that option is selected, many
settings will change instantly, and you will not be able to tell which settings have
changed or what they changed from. Check the manufacturer’s Web site for the
correct CMOS settings for your particular model of PC.
Sometimes people get curious and go into the BIOS setup to see what it looks
like. They also make changes either intentionally or accidentally. What makes it
worse is they generally deny going into the setup program.