| A dead system that gives no signs of life when turned on can be caused by the following: -
Defects in AC power to the system -
Power supply failure or misconfiguration -
Temporary short circuits in internal or external components -
Power supply or other component failure With four suspects , it's time to play detective. Use the procedure outlined next to find the actual cause of a dead system. If one of the test procedures in the following list corrects the problem, the item that was changed is the cause of the problem. Power supplies have a built-in safety feature that shuts down the unit immediately in case of short circuit. The following steps are designed to determine whether the power problem is caused by a short circuit or another problem: -
Check the AC power to the system; a loose or disconnected power cord, a disconnected surge protector, or a surge protector that has been turned off will prevent a system from receiving power. -
Check the AC voltage switch on the power supply; it should be set to 115V for North America. Turn off the power, reset the switch, and restart the system if the switch was set to 230V. -
Check the keyboard connector; a loose keyboard connector could cause a short circuit. -
Open the system and check for loose screws or other components such as loose slot covers, modem speakers , or other metal items that can cause a short circuit. Correct them and retest. -
With ATX/SFX power supplies, verify that the cable from the front-mounted power switch is properly connected to the motherboard. -
Check for fuses on the motherboard ( mainly found in very old systems). Turn off the power, replace any blown fuse on the motherboard with a fuse of the correct rating, and retest. -
Remove all expansion cards and disconnect power to all drives ; restart the system and use a multimeter to test power to the motherboard and expansion slots per Table 5.2, earlier in this chapter. -
If the power tests within accepted limits with all peripherals disconnected, reinstall one card at a time and check the power. If the power tests within accepted limits, reattach one drive at a time and check the power. -
If a defective card or drive has a dead short, reattaching the defective card or drive should stop the system immediately upon power-up . Replace the card or drive and retest. -
Test the Power Good line at the power supply motherboard connector with a multimeter. It's a long list, but chances are you'll track down the offending component before you reach the end of it. |