Fundamentals - Problem: When you apply power, nothing happens. (Page 10 of 14 ) - Verify that the power cable is connected to the PC and to the wall receptacle, and that the wall receptacle has power. Don’t assume. We have seen receptacles in which one half worked and the other didn’t. Use a lamp or other appliance to verify that the receptacle to which you connect the PC actually has power. If the power supply has its own power switch, make sure that the switch is turned to the “On” or “1” position. If your local mains voltage is 110/115/120V, verify that the power supply voltage selector switch, if present, is not set for 220/230/240V. (If you need to move this switch, disconnect power before doing so.)
- If you are using an outlet strip or UPS, make sure that its switch (if it has one) is on and that the circuit breaker or fuse hasn’t blown.
- If you installed an AGP video adapter, pop the lid and verify that the AGP adapter is fully seated in its slot. Even if you were sure that it seated fully initially—and even if you thought it snapped into place—the AGP adapter still may not be properly seated. Remove the AGP card and reinstall it, making sure it seats completely. If the motherboard has an AGP retention mechanism, make sure the notch on the AGP card fully engages the mechanism. Ironically, one of the most common reasons for a loose AGP card is that the screw used to secure it to the chassis may torque the card, pulling it partially out of its slot. This problem is rare with high-quality cases and AGP cards, but quite common with cheap components.
- Verify that the main ATX power cable and the ATX12V power cable are securely connected to the motherboard and that all pins are making contact. If necessary, remove the cables and reconnect them. Make sure the latch on each cable plug snaps into place on the motherboard jack.
- Verify that the front-panel power switch cable is connected properly to the front-panel connector block. Check the silkscreen label on the motherboard and the motherboard manual to verify that you are connecting the cable to the right set of pins. Very rarely, you may encounter a defective power switch. You can eliminate this possibility by temporarily connecting the front-panel reset switch cable to the power switch pins on the front-panel connector block. (Both are merely momentary on switches, so they can be used interchangeably.) Alternatively, you can carefully use a small flat-blade screwdriver to short the power switch pins on the front-panel connector block momentarily. If the system starts with either of these methods, the problem is the power switch.
- Start eliminating less likely possibilities, the most common of which is a well-concealed short circuit. Begin by disconnecting the power and data cables from the hard, optical, and floppy drives, one at a time. After you disconnect each one, try starting the system. If the system starts, the drive you just disconnected is the problem. The drive itself may be defective, but it’s far more likely that the cable is defective or was improperly connected. Replace the data cable and connect the drive to a different power supply cable.
If you have a spare power supply—or can borrow one temporarily from another system—you might as well try it as long as you have the cables disconnected. A new power supply being DOA is fairly rare, at least among good brands, but if you have the original disconnected it’s not much trouble to try a different one.
If you have expansion cards installed, remove them one by one, except for the AGP adapter. If the motherboard has embedded video, temporarily connect your display to it and remove the AGP card as well. Attempt to start the system after you remove each card. If the system starts, the card you just removed is causing the problem. Try a different card or install that card in a different slot.
Remove and reseat the memory modules, examining them to make sure they are not damaged, and then try to start the system. If you have two memory modules installed, install only one of them initially. Try it in both (or all) memory slots. If the module doesn’t work in any slot, it may be defective. Try the other module, again in every available memory slot. By using this approach, you can determine if one of the memory modules or one of the slots is defective.
- Remove the CPU cooler and the CPU. Check the CPU to make sure there are no bent pins. If there are, you may be able to straighten them using a credit card or a similar thin, stiff object, but in all likelihood you will have to replace the CPU. Check the CPU socket to make sure there are no blocked holes or foreign objects present.
WARNING
Before you reinstall the CPU, always remove the old thermal compound and apply new compound. You can generally wipe off the old compound with a paper towel, or perhaps by rubbing it gently with your thumb. (Keep the processor in its socket while you remove the compound.) If the compound is difficult to remove, try heating it gently with a hair dryer. Never operate the system without the CPU cooler installed.
Remove the motherboard and verify that no extraneous screws or other conductive objects are shorting the motherboard to the chassis. Although shaking the case usually causes such objects to rattle, a screw or other small object may become wedged so tightly between the motherboard and chassis that it will not reveal itself during a shake test.
If the problem persists, the most likely cause is a defective motherboard.
 This chapter is from Building the Perfect PC by Robert Bruce Thompson and Barbara Fritchman Thompson (O'Reilly, 2004, ISBN: 0596006632). Check it out at your favorite bookstore today. Buy this book now.
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