In this opportunity I have decided to create a new repair section, which is to repair PC power sources. As the repairs of PC power sources vary depending on the type of failure, what we should always do is identify the type of failure, then raise possible solutions and we become familiar with how to repair and diagnose the failure in these equipment. So today I bring you the first repair of this section that we will solve in the following way:
Equipment: Power Supply ATX 550 W.
Fail: Computer does not turn on.
Diagnosis: It supplies all the voltages but when it is required current it shuts off.
Possible solutions:
1) Capacitor problems, you have to measure the capacitance as the ESR of the electrolytic damper.
2) Resistors altered.
3) Check the oscillator circuit.
Everything described above are the possible scenarios that could be presented to us.
Whenever we go to check a PC power source, the first thing we should do, is to use a 200W lamp in series to the load, which will serve as protection, the way this lamp is used, it is really a serial connection to the feeding of the equipment that we are going to review, in case there is a short the lamp turns on and we avoid damaging any device in perfect condition, besides our security since we could suffer an accident, for that reason it is very important that we always work in a safe way. The next step is to identify at what stage the failure might be. The sources of power have two main stages that we can interpret as a black box, where we have an input and several outputs or technical language would be the primary and secondary, the primary is where the voltage enters the AC (AC) or connection of the network, this transforms that voltage AC to DC, to a DC voltage of approximately 320 VDC, and then introduce it to a transformer that would generate the output voltage (secondary), but to generate the secondary voltage it is necessary that this signal is pulsating or variant in time, since a transformer does not convert DC voltage, is achieved by means of electronic switches, which are usually transistors or mosfet, the most common is the MJE13007 transistor, the order to activate and deactivate these devices are the PWM, who check the status of the electronics in general, in case it finds an anomaly, the PWM gives the order to send the electronics and consequently e our equipment would not work, but it is due to the protection of the PWM. Already having the idea of how a power source works, we can attack the possible solutions. Now what we have to do is connect our source of power to the network, if you turn on the 200 W lamp, it tells us that we have a short circuit and the problem is in the primary, if you do not turn on the lamp we should check two output voltages (secondary), stand bye (violet color) and power on (PW_ON, green color), both must measure 5 VDC, or at least very close to 5 VDC, if this 2 voltages are present, it means that a large part of the primary is working in the right way, then the next step is to turn on our source, to turn it on we make a jumper or short between GND (black color) and power on (green color), if our source does not answer is that the PWM is detecting a short and we would have to check the electronic devices in the output stage, in case our source starts, we measure all the output voltages and little by little we introduce load, again we monitor all the output voltages, s I this tensions begin to fall, we have problems of consumption, this usually fails to give the capacitors and would have to review both the ESR and the capacitance of these 2 devices, with a parameter that this out of its optimal conditions, it is necessary replace it In this repair we had present the voltage of stand bye and power on, the problem was presenting them by consumption, since without load the source worked perfectly, but when connecting it to the computer it is turned off by current consumption, the problem was in 2 electrolytic capacitors of 1uF / 50V, located in the primary, the ESR and the capacitance of these devices was outside their parameters, by replacing these devices solved the failure. It is very important that you follow that series of steps to repair your PC source.
In this channel you will find all kinds of repair from the simplest to the most complex, but the most important thing is that you learn how to repair your electronic equipment, so the invitations to subscribe, activate the bell to be pending notifications, so be alert when upload a new video.
24 июл 2024
