How to Check Computer Power Supply Voltage

How to check computer power supply. troubleshooting

How to check the computer power supply. sooner or later, the moment comes in the life of every amateur radio operator when he has to start mastering minor repair of equipment. It can be desktop computer speakers, a tablet, a mobile phone and some other gadgets. I will not be mistaken if I say that almost every radio amateur tried to repair his computer. Someone succeeded, but someone still carried him to the service center.

PC Power Supply Diagnostics

In this article, we will discuss the basics of self-diagnosis of PC power supply failures.

Let’s assume that we came across a power supply unit (PSU) from a computer. Now you need to find out how check computer power supply. First we need to make sure he is a worker? By the way, you need to take into account that the standby voltage 5 Volts is present immediately after connecting the network cable to the power supply.

If it is not there, then it will not be superfluous to ring the power cord for the integrity of the cores with a multimeter in the sound ringing mode. Also do not forget to ring the button and fuse. If everything is OK with the power cord, then turn on the PC power supply to the network and start it without a motherboard by closing two contacts: PS-ON and COM. PS-ON abbreviated from English. Power Supply On. literally as “turn on the power source”. COM abbreviated from English. Common is common. The green wire is suitable for the PS-ON contact, and the “common” minus is the black wires.

On modern PSUs, there is a 24 Pin connector. On older. 20 Pin.

It is easiest to close these two contacts with a straightened paper clip

Although theoretically for this purpose any metal object or wiring will fit. You can even use the same tweezers.

Power Supply Test Methodology

How to check the computer’s power supply? If the power supply is working properly, it should turn on immediately, the fan will begin to rotate and voltage will appear on all connectors of the power supply.

If our computer malfunctions, then it will be useful to check on its connectors the correspondence of the voltage value on its contacts. Anyway, when the computer crashes and often gets out a blue screen, it would be nice to check the voltage in the system itself by downloading a small program to diagnose the PC. I recommend the AIDA program. In it, you can immediately see whether the voltage in the system is normal, whether the power supply is to blame for this, or, nevertheless, the motherboard “mandates”, or even something else.

Here is a screen from the AIDA program of my PC. As we see, all the stresses are normal:

If there is any decent voltage deviation, then this is already abnormal. By the way, when buying a used computer, ALWAYS upload this program to it and fully check all the voltages and other parameters of the system. Tested on bitter experience :-(.

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If, however, the voltage value is very different on the power supply connector itself, then the unit must be tried to be repaired, but for this you need to know how to check computer power supply. If you are generally very poor friends with computer equipment and repairs, then in the absence of experience it is better to replace it. There are frequent cases when a FAULT power supply unit “pulled” a part of the computer along with it when it failed. Most often, the motherboard fails. How can this be avoided and how to check the computer’s power supply?

I will give a few recommendations for choosing power supplies

On the power supply, you can never save and you should always have a small margin of power. It is advisable not to buy cheap NONAME power supplies.

How to Check Computer Power Supply Voltage

I recommend taking power supplies brands FSP GROUP

They have proven themselves well. I have the FSP at 400 watts.

What if you are poorly versed in brands and models of power supplies, and a new and high-quality mother does not give money))? It is advisable that it has a 12 cm fan, not 8 cm.

Video: How to Check Computer Power Supply Voltage


Power supply with 12 cm fan

Such fans provide better cooling of the radio components of the power supply. You must also remember one more rule: a good power supply cannot be easy. If the power supply is light, then it uses small-sized radiators and such a power supply will overheat during operation at rated loads. And what happens during overheating? During overheating, some radio elements, especially semiconductors and capacitors, change their values ​​and the whole circuit as a whole does not work correctly, which, of course, will affect the operation of the power supply.

Also, do not forget to clean your power supply at least once a year and learn it well. how to check computer power supply. Dust is a “blanket” for radio elements, under which they may not function properly or even “die” from overheating.

The most common BP failure is power semiconductors and capacitors. If there is a smell of burnt silicon, then you need to watch what burned out from diodes or transistors. Defective capacitors are identified by a visual inspection. Opened, swollen, with leaking electrolyte. this is the first sign that it is urgent to change them.

When replacing, be aware that capacitors with low equivalent series resistance (ESR) are in the power supplies. So in this case, you should get an ESR meter and choose capacitors with the lowest ESR possible. Here is a small resistance table for capacitors of various capacities and voltages:

Here it is necessary to select the capacitors so that the resistance value is not more than indicated in the table.

When replacing capacitors, two more parameters are also important: capacitance and their operating voltage. They are indicated on the capacitor housing:

If our power supply starts up, then we measure the voltage at its output connector or connectors with a multimeter. In most cases, when measuring the voltage of ATX power supplies, it is enough to select a DCV limit of 20 volts.

There are two diagnostic methods:

What can we measure and how are these measurements taken? We are interested in measuring the voltage at the indicated points of the power supply, measuring the resistance between certain points, audible dialing for the absence or presence of a circuit, and also measuring the current strength. Let’s take a closer look.

Voltage measurement.

If you are repairing a device and have a circuit diagram for it, it often indicates what voltage should be at the test points on the circuit. Of course, you are not limited only to these control points and you can measure the potential difference or voltage at any point of the power supply or any other repaired device. But for this you must be able to read the diagrams and be able to analyze them. details on how to measure voltage with a multimeter can be found in this article.

Resistance measurement.

Any part of the circuit has some resistance. If, when measuring resistance, the unit on the screen of the multimeter is one, this means that in our case the resistance is higher than the resistance measurement limit we have chosen. Let me give you an example, for example, we measure the resistance of a part of the circuit, consisting conditionally, of a resistor of known nominal value, and a choke. As we know, a choke is, roughly speaking, just a piece of wire with little resistance, and we know the value of the resistor. On the screen of the multimeter we see the resistance is slightly greater than the value of our resistor. After analyzing the circuit, we come to the conclusion that these radio components are working for us and good contact is provided with them on the board. Although at first, with a lack of experience, it is desirable to ring all the details separately. It should also be borne in mind that parallel-connected radio components affect each other when measuring resistance. Remember the parallel connection of resistors and you will understand. You can read more about resistance measurement here.

Sound proverb.

If an audible signal sounds, this means that the resistance between the probes, and accordingly the portion of the circuit connected to its ends, is early to zero, or close to this. With it, we can verify the presence or absence of a circuit on the board. You can also find out whether there is a contact on the circuit or not, for example, in the case of a broken track or not missing, or a similar malfunction.

Circuit current measurement

When measuring the current strength in a circuit, intervention in the board design is required, for example, by soldering one of the terminals of the radio component. Because, as we recall, our ammeter is connected to an open circuit. How to measure the current strength in a circuit can be read in this article.

Using these four measurement methods with a multimeter alone, you can diagnose a very large number of faults in the circuits of almost any electronic device.

As they say, in an electrician there are two main malfunctions: there is contact where it should not be, and there is no contact where it should be. What does this saying mean in practice? For example, when a radio component is burned, we get a short circuit, which is an emergency for our circuit. For example, it can be a breakdown of a transistor. In circuits, an interruption can occur, in which the current in our circuit cannot flow. For example, rupture of a track or contacts through which current flows. It can also be a wire break and the like. In this case, our resistance becomes, relatively speaking, infinity.

Of course, there is a third option: changing the parameters of the radio component. For example, as is the case with the same electrolytic capacitor, or the burning of the contacts of the switch, and as a result, a strong increase in their resistance. Knowing these three types of breakdowns and being able to analyze circuits and printed circuit boards, you will learn how to easily repair your electronic devices. details about repair of electronic devices can be found in the article “Fundamentals of repair”.