- Disassembly Overview
- Electrostatic Discharge (ESD)
- EMI (Electromagnetic Interference)
- Disassembly
- Tools
- Opening the Case
- Cables and Connectors
- Storage Devices
- Motherboards
- Mobile Device Issues
- Reassembly
- Preventive Maintenance
- Basic Electronics Overview
- Electronics Terms
- Power Supply Overview
- Power Supply Form Factors
- Purposes of a Power Supply
- Power Supply Voltages
- Mobile Device Travel and Storage
- Mobile Device Power
- ACPI (Advanced Configuration and Power Interface)
- Replacing or Upgrading a Power Supply
- Symptoms of Power Supply Problems
- Solving Power Supply Problems
- Adverse Power Conditions
- Adverse Power Protection
- Surge Protectors
- Line Conditioners
- Uninterruptible Power Supply (UPS)
- Standby Power Supply (SPS)
- Phone Line Isolator
- Electrical Fires
- Computer Disposal/Recycling
- Soft Skills?Written Communications Skills
- Chapter Summary
- Key Terms
- Review Questions
- Exercises
- Activities
This chapter is from the book
This chapter is from the book
This chapter is from the book
Solving Power Supply Problems
When you suspect that the power supply is causing a problem, swap the power supply, make the customer happy, and be on your way! Power problems are not usually difficult to detect or troubleshoot.
Do not overlook the most obvious power supply symptom. Start by checking the computer power light. If it is off, check the power supply’s fan by placing your palm at the back of the computer. If the fan is turning, it means the wall outlet is providing power to the computer and you can assume that the wall outlet is functioning. Check the motherboard for LEDs and refer to the manual for their meaning. Test the power outlet with another device. Ensure that the power cord is inserted fully into the wall outlet and the computer. If you suspect that the wall outlet is faulty, use an AC circuit tester to verify that the wall outlet is wired properly.
TECH TIP: Do not disassemble a power supply
Power supplies are not normally disassembled. Manufacturers often rivet them shut. Even when a power supply can be disassembled, you should not take it apart unless you have a background in electronics.
On a mobile device that is running on battery power, check the battery charge icon through the operating system. Try using the device on AC power. If it works on AC power, try recharging the battery. If the battery does not recharge, replace it. Wiggle the AC power to see if the connection is loose. Remove the battery for a moment and then re-insert it (and attach AC power if battery power does not work). On a laptop, see if the power brick has a power light on it and whether it is lit. Try a different AC adapter from the same manufacturer because AC adapters are proprietary between laptop vendors.
If a mobile device or smartphone won’t power on after recharging the battery, remove the battery for about a minute. Reinstall the battery and try powering on again. If the system will still not power on, try powering on with the power cable attached. If the system works with the power cable attached, the battery probably needs to be replaced.
The following troubleshooting questions can help you determine the location of a power problem:
- Did the power supply work before? If not, check the input voltage selector switch on the power supply and verify that it is on the proper setting.
- Is the power supply’s fan turning? If yes, check voltages going to the motherboard. If they are good, maybe just the power supply fan is bad. If the power supply’s fan is not turning, check the wall outlet for proper AC voltages.
- Is a surge strip used? If so, check to see if the surge strip is powered on, then try a different outlet in the surge strip, or replace the surge strip.
- Is the computer’s power cord okay? Verify that the power cord plugs snugly into the outlet and into the back of the computer. Swap the power cord to verify that it is functioning.
- Is the front panel power button stuck?
- Are the voltages going to the motherboard at the proper levels? If they are low, something may be overloading the power supply. Disconnect the power cable to one device and recheck the voltages. Replace the power cable to the device. Remove the power cable from another device and recheck the motherboard voltages. Continue doing this until the power cord for each device has been disconnected and the motherboard voltages have been checked. A single device can short out the power supply and cause the system to malfunction. Replace any device that draws down the power supply’s output voltage and draws too much current. If none of the devices is the cause of the problem, replace the power supply. If replacing the power supply does not solve the problem, replace the motherboard.
If a computer does not boot properly, but it does boot when you press 
+ 
+ 
, the power good signal is likely the problem. Some motherboards are more sensitive to the power good signal than others. For example, say that a motherboard has been replaced and the system does not boot. At first glance, this may appear to be a bad replacement board, but the problem could be caused by a power supply failing to output a consistent power good signal.
TECH TIP: Check the power good (sometimes called power OK) signal
Check the power supply documentation to see if the power supply outputs a power good signal (rather than the normal +5 volts). Turn on the computer. Check the power good signal going into the motherboard power connector. Do this before replacing the motherboard. A power supply with a power good signal below +3V needs to be replaced.
Sometimes, none of these troubleshooting actions work. A grounding problem might be the issue. Build the computer outside the computer case, on an antistatic mat, if possible. Start with only the power supply, motherboard, and speaker connected. Even though it will normally produce a POST audio error, verify that the power supply fan will turn. Most power supplies issue a click before the audio POST beeps. Next, verify the voltages from the power supply. If the fan turns and the voltages are correct, power down the machine and add a video adapter and monitor to the system. If the machine does not work, put the video adapter in a different expansion slot and try again. If placing the video adapter in a different expansion slot does not work, swap out the video adapter.
If the video adapter works, continue adding devices one by one and checking the voltages. Just as any one device can cause the system not to operate properly, so can any one adapter. If one particular adapter causes the system to malfunction, try a different expansion slot before trying a different adapter.
If the expansion slot proves to be a problem, check the slot for foreign objects. If none are found but the problem still occurs, place a note on the expansion slot so that no one will use it.