Computer Repairs – Diagnostics Power Supply June 4, 2016 at 8:15 am
In case of failure the power supply the right choice when repairing a computer – replacing the power supply to the new. However, consider the most frequent causes of failure of power supplies. Computer Services, who has worked for more than 5 years makes the following recommendations: The most likely breakdown of the rectifier diode bridge in the high-voltage circuit. Power supply for such a defect is completely dead: no one from the supply voltage (including the "duty" of five volts), and inclusion – there are no sounds and movements. The reason is determined by any ohmmeter if the resistance between any two terminals of diode bridge is less than 1 ohm and the same in both directions – the bridge needs to be changed. Along the way, need to be replaced and a fuse in such breakdowns it usually burns up the food chain only if the computer was not protected by automatic reactivation fast defense. As a replacement will fit almost any bridge rectifier diodes, or individual, calculated for a voltage above 300 volts and a current of 1 amp, but do not rush to include food – may cause deeper. The second extent of failure – the breakdown of the individual diodes in secondary rectifying circuits.
External manifestations of such a failure – the existence of "duty" of voltage and weak signs of life: when you press the power button once fan twitches, but nothing more occurs. In this case, the actual converter is working normally. Ohmmeter will help you: pierced diode or diode assembly is easy to detect, not vypaivaya at virtually zero resistance in both directions. If you using a multimeter, which allows you to check the serviceability by measuring the diode forward voltage drop, do not be surprised too low value of that of the diode arrays main channels – there are applied Schottky diodes with a fall of about 0.1 volts. Unfortunately, the assembly on 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 used conventional diodes, but do not forget that the converter operates at a frequency of 200 kHz, so that the diodes should be high frequency. Another part of the reason the output of Power failure can be determined visually, these include the breakdown of electrolytic capacitors (rupture of the shell, mostly – at the top) and protective varistors. Capacitors, of course, be changed, and varistors – because they do not there is always the same – you can just vypayat (remembering that the unit is left without protection from the next major power surge). The breakdown of high voltage transistor switches, which 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 entrust the maintenance and configuration of your computer professionals. Rely on your PC repair professionals.