The computer does not turn on: the problem is in the power supply
All PC malfunctions falling under the “computer does not turn on” category boil down to one single problem: it is impossible to download any of the known operating systems to the computer, including the MS-DOS boot disk and the secure MS Windows product. The “symptoms” of this problem are as follows:
the monitor remains dark;
PC does not respond to user actions;
after trying to turn on the PC, it screeches frighteningly or reports some kind of error.
If you are familiar with all of the above, then it is entirely possible that the problem lies in the power supply, from which, in fact, every computer starts.
Power Supply: Diagnostics and Problems
If you think that the power supply is a certain box stuffed with radioelements that passively converts one voltage to another, then you are mistaken. In fact, PSU is a self-contained intellectual subsystem of a computer.
Normally, the voltage supply to the PC input is as follows: the plug is traditionally inserted into the outlet, after which the power supply is turned on and produces the optimal voltage, the strength of which is sufficient to provide low-power computer microcircuits. As a result, a certain amount of PC elements is under a small voltage. This should be remembered and before starting the diagnostics of the power supply, turn off the system unit from the network.
No voltage is supplied to the PSU
Some modern motherboard (system) boards are equipped with a LED, which responds to a voltage supply. If the PSU is turned on, but the LED does not light up, this usually means that the PSU is faulty. If there is no LED, then you can check if the voltage is coming to the PSU using the tester.
PSU does not provide power
If after pressing the power button of the computer its PSU stubbornly “silent” (the fan either does not work at all, or stops after a couple of seconds), the problem may be as follows:
PC power button does not work – then try manually connecting the PWR contacts on the motherboard;
The PSU cannot provide the power required for the system to work – turn off the hard drives, disconnect the bulk drives and video card, and then repeat the power-up procedure again;
The PSU is completely faulty – if the BIOS is copm, then in this case it starts to squeak.
The power supply is not to blame?
Each PSU has a built-in circuit that protects the unit from short circuit and, in case of occurrence, turns off the PSU. Therefore, if the unit does not work, it is entirely possible that it was not his fault at all, but the “flying” motherboard or some kind of peripheral device. And in the PSU, circuit protection is simply triggered. To find out whether it is or not, turn off the peripherals in turn and repeat attempts to start the computer between disconnections.
Power supply quality is continuously monitored. When the voltage drops at least for an instant in the network, this, as a result, leads to a drop in the voltage that the power supply produces. This situation resets the Power Good signal from the motherboard (similar to pressing the Reset button on the PC), thereby preventing the system board processor from working. If you see that there is a PG signal, but the computer still does not “start up”, then the PSU definitely has nothing to do with it (or its quality leaves much to be desired) and the problem should not be looked for in it.
Lack of power
If the computer starts to reboot when a large load is applied to it, but at the same time, the voltage supplied by the unit is 5–10% below the norm, then, apparently, the PSU is simply not able to “pull out” the system due to lack of power.
In addition, you should know the “age” of the PSU, because over time the unit “passes”, which leads to a decrease in the power level necessary for the performance of PC components. If you don’t know the “age” of the block, test it using the S&M utility tools or disable unnecessary hard drives and optical drives (if the problem disappears, your block starts to “age”).
Remember that PC power supplies are far from omnipotent, and this is especially true for low-cost devices. There is a real mess in our power grid, and dealing with it is not easy; even line filters are useless here. Alas, the “miracles” of tension can lead to sad consequences, although a burnt filter is still more “pleasant” than a burnt out computer or monitor. To avoid problems, it is recommended to use uninterruptible power supplies.
Many PSUs, and especially “old ones,” cannot fully work without proper load. In case you want to turn on the unit without the motherboard assembly, take care of the load: connect at least the railway. By the way, the “empty” block is turned on by closing the green wire with any of the black wires on the main ATX connector.
If you assume that the power supply unit is malfunctioning or is not able to function normally, one very effective way will finally help to verify this: replace the “suspicious” PSU with a knownly good and powerful one – and see what happens. Comp “wound up”? Excellent! Not? Then the problem is still not in the block.