File Name: computer power supply problems and solutions .zip
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Although most complex computer issues at work can often be solved by the business IT support team, there are many other small, but common, issues that occur on a regular basis on a personal computer. The good news is that many problems with computers have simple solutions, and learning to recognise a problem and fix it yourself will save you a lot of time and money. The Screen is Blank If the computer is on but the screen is blank, there may be an issue with the connection between the computer and the screen. First, check to see if the monitor is plugged into a power point and that the connection between the monitor and computer hard drive is secure.
You must unplug your ATX power supply from the wall before working inside the case. The power supply troubleshooting chapter below is from my book, "Computer Repair with Diagnostic Flowcharts, Third Edition.
ATX Power Supply Failure Diagnostics Note that these steps correspond with decision points on the flowchart and are reached directly by clicking on the diamond symbols. The text below cannot be read sequentially. The first step in the troubleshooting process is simply determining if the power supply is coming on. You can usually hear the mechanical components in PCs that make rotational noise when they are powered up. Noise makers include the hard drive, as its electric motor spins up the platters, and plenty of fan noise is normal for PCs without PWM Pulse Width Modulation fans.
Your PC should also give a single beep if it passes its internal start-up diagnostic, and there are always status LED's to tell you the system is on, though some home PC builders don't bother connecting them. If your hearing isn't good, you can check to see if the power supply fan is creating a breeze.
Monitors are powered independently, so unless you're looking at a notebook PC, a live screen doesn't indicate a working power supply. Return to Diagnostic Chart If your computer has a display connected, can you get a live screen, whether it's a simple text message or a colorful splash screen?
If the display shows a message like "No video signal detected," that's the monitor telling you the video port isn't communicating, so you should follow the "No" path for this decision. Sometimes a CRT or older LCD may show a multiplicity of images or endless scrolling, which means the video adapter is alive and trying to transmit an image but the monitor can't interpret the signals. This doesn't happen as often with modern LCDs or expensive CRTs that can match a large range of inputs for higher screen resolutions set in Windows.
If you are using a high definition TV for your primary display, do yourself a favor and use a standard monitor for troubleshooting until you eliminate the power supply as an issue.
The primary culprits are multi-core CPUs that can consume anywhere from 10W to 50W or more per core, for a total CPU consumption as high as W in a single processor system. Meanwhile, PCI Express graphics cards for gaming can pull as much as Watts by themselves, or double that in a dual card configuration.
While PC power supply manufacturers boast about their power rating since it's their main selling point, manufacturers of video cards and other components don't trumpet their power consumption. You may have to do a little math to work it out. Sometimes they give the peak current requirement in Amps A at the supply voltage, usually 12V, so you multiply the two numbers for the power consumption in Watts. All of the high end video cards require more power than can be supplied through the PCI Express slot on the motherboard, so they are fed directly from the power supply with one or two 6-pin PCI Express supplementary connectors.
Older video adapters employed the 4-pin Molex drive connectors. A quick search online will help you find a number of calculators for determining your power supply requirement based on the components installed. If the power supply boasts of a peak power rating, don't use that as your guide.
Peak power is not sustainable, it's only a meaningful metric for electrical devices with transient demands, like electric car motors that can safely exceed their maximum power rating for short periods during acceleration.
Return to Diagnostic Chart If the power comes on but the screen never goes live, try switching back off again and retrying. The switch programming may require you to hold the power button in for a few seconds before the power supply shuts down again. If it refuses to power down, check if there's an override switch on the back of the supply. Otherwise you can turn off your power strip, if you're using one, or just pull the plug. This signal allows the CPU to shut itself down if power becomes unstable during regular operation.
Any longer strings of beeps are usually due to a hardware failure or something pressing down a key on the keyboard and the beep codes depend on the manufacturer. Long strings of slow beeps are usually related to a bad memory module, and repeating strings of 3 or 9 beeps often indicate video card failure. In either of these cases, shut down, unplug, and try reseating either the RAM or the video adapter, though it can't hurt to do both. If you are getting beeps with a live screen, the problem is unlikely to be power supply related.
Return to Diagnostic Chart If you've done any work in the case immediately before the boot failure, undo it, even if it means swapping the old component back in. The boot failure may be unrelated to the new component, but you could have dislodged a connector, left a loose screw rolling around, or unseated an adapter while working in the case.
Return to Diagnostic Chart A noisy power supply fan can usually be cleaned or replaced easily enough, though you have to watch out for the big capacitors in the power supply when you open it up, even after it's unplugged.
Case fans can also fail and make noise, as can the heat sink fans on the CPU, video adapter, or motherboard chipset. And make sure the fan noise isn't due to something stuck in the grille and hitting the fan blades. If your kids hear a whistle that you don't, it's probably beyond your hearing range, and it's not necessarily in the power supply either. I tend to leave these things alone on older PCs if they aren't bothering anybody.
High quality power supplies ship with PWM Pulse Width Modulation fans, which are capable of running at much lower RPMs than fans that are controlled by the voltage level. Fans with two or three wires can only be controlled by varying the input voltage. PWM fans can typically run down to about a quarter of their rated speed, where voltage controlled fans will usually cease working well before dropping to half of their rated speed. It makes a huge difference in noise output when the higher air circulation, measured in CFM Cubic Feet per Minute isn't required.
Return to Diagnostic Chart If you get a text message on the screen that makes any reference to the hard drive, the controller, a SMART error, or any message mentioning the operating system, missing files, etc, proceed to the ATA Drive Failure flowchart. If your power supply is chronically noisy with whistling capacitors or hums, that may be reason enough for you to replace it.
And if you've been through the other flowcharts because your PC locks up or reboots at random times, the problem could well be the power supply quality, even if it usually boots the PC.
If you have experience working with a Digital Volt Meter around live voltages, you can try checking the voltages right at the top of the connector to see if they are within reasonable tolerance of the rated voltages. It depends on whether your probe is thin enough and how much room there is next to each wire at the top of the connector to insert the probe.
Unfortunately, a simple DVM won't show you whether there is AC ripple on the DC voltages, which can cause all sorts of problems if it's bad enough. This test also requires back-probing the ATX connector or introducing a break-out box between the ATX connector and the motherboard.
The test must be performed with the power supply attached to the motherboard for a live load and is only recommended for experienced techs. Unstable voltages and AC ripple on the DC are real ghosts in the machine, and can mimic all sorts of other problems. If you get into a flaky failure situation that you can't diagnose and you've already started swapping parts, you may as well try a new power supply as well.
I've seen power supplies produce some really bizarre failures, like a PC that reboots when you set your coffee cup down too hard on the table. The most pervasive of the unstable power supply problems are random lockups or spontaneous reboots. Return to Diagnostic Chart If power isn't coming on, take the time to double check that the cord is plugged into a live socket and firmly seated in the back of the power supply.
Unplug the power supply cord from the outlet and plug a working lamp into the very same socket to test it. Don't assume that all the sockets in a power strip are working just because the power strip status light is lit. I'm always coming across power strips with one or more bad outlets.
The power supply cord is basically bullet-proof, unless you cut through it with something, but if the PC gets moved or the cord gets kicked, it's easy for that cord to pull out a bit from the socket on the back of the power supply and still look like it's plugged in. Return to Diagnostic Chart Newer , high quality power supplies are generally termed "universal input" or "full range" and will work on any AC voltage from 90V to V at 50 Hz or 60 Hz.
While supply voltage shouldn't be an issue with a previously working PC, if you've replaced the power supply or moved the system, it's always a possibility. You should always unplug the power supply cord before changing the voltage because modern ATX power supplies are always live when plugged in.
While it's not recommended that you experiment, if you plug the power supply with the switch on V into the socket in a V country like the U. But if you power on a supply set for V in a country with a V distribution, you'll probably blow the power supply fuse at the very least , and potentially damage the supply and the connected components.
Return to Diagnostic Chart One obvious reason the PC won't turn on when you press the switch is if the switch lead has separated from the motherboard.
This lead is usually labeled PW-ON or PW and it reaches from the front the PC case to a small block of metallic pins for case connections to the motherboard. It's not at all uncommon to encounter this problem if you've done any work inside the case because the leads aren't glued in place and the connectors aren't tight. Even if you've built a number of PCs in your life, it's normal to get this connection wrong when you replace or install a new motherboard due to poor identification of the pins in the connector block.
On the bright side, it's a non-polarized switch so you only have to pick the correct two pins, not the orientation. I've come across cases where the printed book that ships with a new motherboard disagrees with the printing on the motherboard itself as to the function of different pin sets in the connector block. I always go with the motherboard labeling in those cases.
Return to Diagnostic Chart Check that the power switch is really working by using a meter on the continuity setting, or just check for a short when the switch is closed if your meter only measures Ohms. The switch is just a binary logic input for the motherboard which is always partially live in an ATX system that's plugged in.
The motherboard follows its programming to tell the power supply to come on full or to shut down, depending on the settings. The same switch may be used to wake the PC from stand-by mode.
This doesn't apply to obsolete AT PCs, where you'll see the heavy power cord going to a large switch, but those systems are pretty much gone. When I'm troubleshooting the power switch in an ATX system and I don't have a meter with me, I just short across the two pins for the power switch in the motherboard connector block with a screwdriver to see if the system will start.
Since it's a live power test, don't try it if you aren't comfortable working with live equipment and might jerk away in surprise when the power does come on. You could end up stabbing the motherboard or the video adapter with the screwdriver, just from reflexes, and do serious damage.
When you encounter a failed switch and don't have a replacement on hand, you may be able to scavenge the hard reset switch present on older cases. If you believe the motherboard was badly damaged by a power surge or a short, it's possible the switch circuit has failed or that the power supply is immediately shutting off to protect itself from a high current draw.
But switching power supplies require a load to operate so you must keep the hard drive connected. If you press in the power switch on your system and it doesn't immediately shut off the PC, that's how ATX systems are supposed to work. The normal setting for PC power switches makes you hold the switch in for three to five seconds to shut down the system. Pressing the switch for a shorter duration might put the system in sleep mode or wake it up from hibernation, important options for power conservation.
If Windows fails to turn off the power when you select "shut down," it's usually due to a corrupted file or bad setting in the operating system. The first thing to try is running "System Restore" to a date prior to when the problem appeared. Windows may also fail to shut down if an external USB device, often a back-up hard drive, has been installed without the proper software drivers or is sharing a USB port. It's easy enough to troubleshoot USB shut down issues by disconnecting those devices one at a time.
Return to Diagnostic Chart Modern motherboards require multiple connections from the power supply, starting with the main 24 pin ATX connector that replaced the older 20 pin connector in most designs. Power hungry CPUs and chipsets have led to a variety of supplemental connectors, including a 4 pin or 8 pin ATX 12V supply on many systems, and multiple 6 pin PCIe connectors for serious graphics cards.
With the power supply unplugged, make sure all motherboard connectors are properly seated and latched by removing them and reattaching. I've always found the standard latching system for the main power connector to be counter-intuitive. It works kind of like a see-saw with a pivot, you have to squeeze in at the top to pop it open at the bottom.
They usually don't make any noise on releasing, but you should get a satisfying click when you remake the connection. ATX Version 2.
After all, it is the source of power. This little box feeds different amounts of power to all the components on your PC. All you need to do is plug it into the wall and into your motherboard and you have power. Alternating: an electric current that reverses its direction many times a second at regular intervals. Other specs include the amount of energy that the unit can supply. This is measured in watts. There is also a switch on the back of the unit which could alternate the accepted voltage.
Modern personal computers universally use switched-mode power supplies. Some power supplies have a manual switch for selecting input voltage, while others automatically adapt to the mains voltage. Most modern desktop personal computer power supplies conform to the ATX specification , which includes form factor and voltage tolerances. While an ATX power supply is connected to the mains supply, it always provides a 5- volt standby 5VSB power so that the standby functions on the computer and certain peripherals are powered. ATX power supplies are turned on and off by a signal from the motherboard.
Orders delivered to U. Learn more. Troubleshooting the power supply basically means isolating the supply as the cause of problems within a system and, if necessary, replacing it. It is rarely recommended that an inexperienced user open a power supply to make repairs because of the dangerous high voltages present. Even when unplugged, power supplies can retain dangerous voltage and must be discharged like a monitor before service. Such internal repairs are beyond the scope of this book and are specifically not recommended unless the technician knows what he is doing. Many symptoms lead me to suspect that the power supply in a system is failing.
Many power problems originate in the commercial power grid, which, with its become increasingly sensitive to even minute changes in the power supply more than enough to cause an entire computer motherboard to stop dead A common solution to capacitor tripping is the installation of line reactors or chokes that.
You must unplug your ATX power supply from the wall before working inside the case.
Power supply problems can be difficult to diagnose if you don't know what to look for. Here are some suggestions on how to quickly spot a faulty supply and how to replace it. A bad power supply can be the root of many PC problems. Experience can help a tech diagnose problems caused by a faulty power supply that would normally be overlooked by a novice. This article outlines how to diagnose a faulty supply by testing its voltage outputs, as well as how to replace the defective unit. The symptoms Just about any intermittent problem can be caused by a faulty power supply.
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 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.
- А как же принцип Бергофского.
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