In case of failure the power supply the correct choice for computer repair – replacement power supply for a new one. However, we consider the most common causes of failure of power supplies. Computer Services, with experience of more than 5 years gives the following recommendations: The most likely breakdown diode rectifier bridge to high-voltage circuit. Power supply for such a defect is completely dead: there is not one of supply voltages (including the "duty" of five volts), and inclusion – no sounds and movements. The reason is determined by any ohmmeter: if the resistance between any two terminals of the diode bridge is less than 1 ohm and the same in both directions – the bridge needs to be changed.
Incidentally need to be replaced and a fuse for these breakdowns it is usually consumed, unless the food chain computer was not protected by circuit breaker is activated quickly. As a replacement suit almost any rectifier bridge or individual diodes, the voltage above 300 volts and a current of 1 amp, but does not include meals in a hurry – perhaps deeper reason. Second on the extent of failure – the breakdown of separate diodes in secondary rectifier circuits. External manifestations of such a failure – the existence of "duty" of voltage and weak signs of life: when you press the power button the fan once twitches, but nothing more occurs. In this case, the actual converter is working normally. Will help you ohmmeter: punched diode or diode assembly is easy to detect, not by almost zero resistance in both directions. If you using a multimeter, which allows you to check the serviceability of the diodes by measuring the forward voltage drop, do not be surprised too low for such diode arrays main channels – where applicable Schottky diodes with a drop of about 0.1 volts. Unfortunately, the assembly on the Schottky diodes can be replaced only similar, ordinary diodes here will not help – they have too much power dissipation, in addition, will be considerable variation stresses in the channels.
In the negative supply chains, the normal diode, but do not forget that the converter operates at a frequency of 200 , so that the diodes should be high frequency. Another part of the reasons for exit block Power failure can be determined visually, these include the breakdown of electrolytic capacitors (rupture of the shell, more often – from the top) and protective varistors. Capacitors, of course, be changed, and varistors – because it does not there is always the same – you can just vypayat (remembering that the unit is left without protection from the next major power surge). Breakdown of high-transistor, which is a few years ago it was possible put in the first place, now rare: the element base is not static, and the current transistors rarely fail on their own. There are other possible reasons, but for their diagnosis would take at least oscilloscope, and connect with their removal is economically inexpedient. In any case it is better to trust computer repair professionals.