The simplest power supply unit converts AC electricity from a wall outlet into four types of direct current (DC) voltage, which a computer typically uses. In addition to this, the power supply unit (PSU) also provides cooling of the desktop PC with a fan. If the actual parameters do not meet the above standards, it fails, and then the power supply needs repair.
ATX Power Supplies
Features such as Power Saver and Hibernation are made possible by ATX sources compatible with motherboards. They support low-energy modes, which allow you to temporarily record or cache data when the computer is in sleep mode. ATX power supplies support six voltage settings, which include +5 volts, -5 volts, +12 volts, -12 volts +5 volts in standby mode and +3.3 volts. This wide range is implemented by an external adapter and internal power supply (IP).
A laptop adapter converts electricity from a wall outlet to an internal power supply with parameters that it can use. This is usually a higher DC voltage than the input power. The adapter regulates the power, mainly from 10 to 18 volts DC, after which the internal PSU then regulates the voltage in accordance with the needs of the computer. With advances in software, PC power modes are also being upgraded. For example, almost all modern computers support Power-Save or Sleep. These modes allow you to turn off the computer with the software, and not use the button.
Laptop Power Sources
The device of the laptop power supply is slightly different from that used on the desktop PC. Power is plugged into the back of the computer, which connects it to the metal tracks inside the motherboard. They are connected to voltage regulators that produce 5 volts, 12 volts, 3.3 volts and CPU voltage. They will be connected to cylindrical capacitors distributed throughout the motherboard. Capacitors act like tiny fast batteries, providing extra power where necessary to maintain constant voltage during high consumption.
These parameters need to be controlled to carry out effective repairs of the laptop power supply yourself. Usually the power source is a little warm. If it is hot, then something is wrong with it or with the component on the motherboard.
Condensers can be seen through the ventilation gaps in the power supply. It is important to look at the top of them. If it is flat and shiny, then everything is in order. If it is uneven, has a darker color or the liquid coming from it, then these are signs of a faulty capacitor, and then an urgent need to repair the power supply. Experts do not recommend opening a computer IP if the user does not have the appropriate knowledge.
Diagnostics of power supply systems
The quickest diagnosis is to simply replace the IP, and then observe how the system behaves. But before you do this, you need to do a few tests. First you need to check the CPU power line. It makes no sense to replace the PSU when there is a short circuit in the CPU power line. To do this, you can use a multimeter and check the resistance of the 4-pin auxiliary connector. Usually the resistance in the connector on the motherboard is close to infinity. When the multimeter is connected for the first time, it will show 150 ohms, and then quickly grow to infinity. This is normal, and so it should be on the motherboard, on which there is no power.
The second thing to check is the processor resistance. Usually it is about 7 ohms or more. Less than 4 ohms indicates a CPU error, so to fix it, you need to repair the power supply. A CPU error can sometimes look like a PSU error when the system shuts down immediately after being turned on. This is because the IP has a short circuit protection and does not start at all if the short circuit is on any power lines.
A check of the output voltage indicates whether it is within the acceptable range. In this case, the voltage of the IP is measured with the load connected, which means testing when the unit in the system is connected to the motherboard and peripheral devices.
Overloaded power supplies
A weak source can interfere with user plans to increase machine power. Some systems are designed with powerful IPs for future expansion. However, some weak systems from the very beginning cannot adequately serve energy-intensive processes, and the user will have to repair the gs power supply from time to time.
Power ratings can sometimes be deceiving. Not all 300-watt supplies match their capacity. Not all cheap IPs can actually reduce the rated power; they provide noisy or unstable operation, which causes problems with the system. Repeated heating and cooling of solid-state components ultimately leads to a computer system failure, the hotter the PC, the shorter its service life.
Since power supplies have common form factors, finding a large replacement for most systems is easy, you just need to know the basics of the device and repairing the power supply. If system noise is a problem, models with special fans will help get rid of it, as they work more quietly than standard devices. Power supplies that use larger diameter fans rotate more slowly and quietly, but at the same time move the same amount of air as less efficient fans.
Today, many processors use passive heatsinks that require a constant flow of air to cool the chip. If the processor heatsink has its own fan, this does not cause much concern. If there are free expansion slots, the user must evenly divide the boards in the system in order to distribute the air flow between them. Special designs with additional cooling fan power can also help.
Common PC problems
Any problem with a frequently shutting down system is most often caused by IP. Do-it-yourself computer power supply repairs can only be done by examining the symptoms of a failure. The following symptoms indicate PI:
- Any sudden power outages.
- Unauthorized PC reboot or memory check.
- Hard drive and fan do not work, +12 V is missing.
- Fan Failure.
- Small reductions that lead to a system reset.
- An open circuit in the power supply to the system case or connectors - you need diagnostics of the power supply, repair and adjustment.
- The presence of static discharges that disrupt the operation of the PC.
- Erroneous recognition of bus powered USB peripherals.
- System completely dead (no fan, no cursor), smoke.
Trouble-shooting
Before repairing the power supply, you need to remember that even when the power is turned off, it can retain dangerous voltage and must be discharged (like a monitor) before servicing. The following is a simple flowchart to help you avoid common power problems:
- Check AC input. Make sure that the cord is firmly fixed to the wall outlet and to the IP socket.
- Try another cord.
- Check DC power connections.
- Make sure that the connectors on the motherboard and drive are firmly attached and in good contact.
- Check loose bolts.
- Check DC output power.
- Use a digital multimeter to check the correct voltage, if specified in the specification, replace the power supply.
- Check installed peripherals.
- Remove all boards and drives and retest the PC. If it works, add the elements back one at a time until the system works again.
- The last item added before the failure returned is most likely faulty.
If the symptoms and problems disappear, the user has found the source of the problem and performed the repair of the power supply with his own hands.
Reverse Sensing Connectors
To measure voltages on an existing system, the user can apply a method called reverse sensing on the connectors. You can not disconnect the connectors when the system is functioning, so you need to measure the voltage. Almost all the connectors that are needed for sensing have holes where the wires enter the connectors. Metric sensors are quite narrow to fit into the connector next to the wire and contact the metal terminal inside. This method is called reverse sensing, because it examines the connector from the back, which is especially effective before repairing the laptop power supply.
To test the power supply for the correct output, check the voltage at the Power_Good pin (P8-1 on AT, Baby-AT and LPX, pin 8 on the ATX connector) for power from + 3 V to + 6 V. If the measurement is not in this range , the system does not see the Power_Good signal and therefore does not start properly. In most cases, the PSU is bad, you can replace it or repair the power supply yourself. Next, you need to measure the voltage ranges of the contacts on the motherboard and PSU connectors.
If the user measures voltages for testing purposes, any reading within 10% of the specified limit is considered acceptable, although most manufacturers of high-quality power supplies indicate a stricter 5% tolerance. For ATX power supplies, the specification requires that the voltages be no more than 5% of the nominal, with the exception of 3.3 V, which should be no more than 4%. If the measured voltages do not correspond to these ranges, the power supply must be replaced.
Specialized Testing Equipment
Specialized test devices can be used to test the power supply more efficiently, since it is one of the elements of the system that is most prone to errors. These typically include a digital infrared thermometer and an alternating voltage transformer. This thermometer measures the sensitivity of infrared energy without having to touch the element that it reads.
This allows you to instantly check the temperature of a chip, board, or system chassis. An alternating voltage transformer is a useful test device for checking before repairing the computer’s power supply unit with your own hands, since it allows you to monitor the voltage of the AC network used as input to the power source. This device consists of a large transformer installed in a housing with an indicator that controls the output voltage. The power cord from the transformer is inserted into the outlet and the PC power cord is connected to the socket installed on the transformer. The handle on the transformer can be used to adjust the AC voltage that the PC receives.
Most AC transformers can adjust their AC outputs from 0 V to 140 V, no matter what the voltage at the AC input. Some can range from 0 V to 280 V. You can use a transformer to simulate shutdown conditions, allowing you to observe the response of a PC. By starting the PC and lowering the voltage until the PC turns off, you can see how much reserve the power source has to handle fluctuations or other voltage fluctuations. If the transformer can output voltages in the 200 V range, you can check the possibility of the power supply working at external voltage levels.
Inadequate system cooling
Some power supplies have more powerful cooling fans, which can minimize problems with overheating, especially for hotter processors. Ventilation in the system is very important. In most prefabricated systems, they are not a concern, as leading manufacturers ensure that their systems are adequately ventilated to avoid overheating.
The location of the system may affect cooling. It is not recommended to place the system on carpet, as most chassis are designed to pull air in the lower part of the front panel, which can be easily blocked or clogged with carpet fibers. If the user is forced to put the system on the floor, it is recommended to lift it, at least through some platform. When working on a PC, you need to monitor the situation and not maximize power with additional equipment that is installed.
Service life extension
There are several things that can help you get the most out of your power source. The user can extend the life of the IP beyond the manufacturer’s warranty, but this will not last forever.
The power source must exceed the requirements of the system by at least 20%, it must be kept clean and at low temperatures. Air quality in some rooms may be poor, so use an air filter. Sometimes cleaning the system significantly extends the life of the PC. The computer must breathe, or it will overheat and die.
Some computers, such as servers, gaming systems and high-end PCs, have several power supplies and fans. This meets two needs: increased demand for power due to high speed or high loaded components and increased cooling capacity because they generate a lot of heat. This type of equipment is often used with overloaded PCs.