PC source solution that does not turn on (Power ON Fault)

PC source solution that does not turn on (Power ON Fault)
Technique link to repair PC source
• Técnica para reparar f...
Continuing a bit with the issue of PC source repairs, this time I bring you how to repair a PC power source, when it turns on.
The problem with this power source is that the Power ON voltage is very low, and usually this pin should measure approximately 5 VDC. Whenever we go to check a PC power source, the first thing we must verify is the voltage of Stanby and Power ON, these signals are measured when connecting the source to the network. If the source generates Standby, it must automatically generate Power ON, since it depends on Stanby. The problem that arises in the source is that we have Stanby, but the Power ON measures 3V; this voltage is low and when plucking the source between Power ON and GND, it does not start, problems that we must solve. To solve this fault we identify which type of chip the source uses, because in this way it gives us a small idea of ​​how the Power ON signal is configured. This source uses the SDC7500 chip, which is equivalent to the TL494, it also uses the SDC339, which internally has four comparators. Redrawing the connections of Power ON and comparing them with a similar circuit, notice that the chip SDC7500, must generate a voltage of 5VDC, this voltage feeds the SDC339, when this signal is measured in the source, it is verified that it measures 3 VDC, which is why it makes the SDC339 not work. As the SDC7500 does not generate the 5VDC, this chip was replaced, when doing the measurements again we observed that 4.98VDC was already generated to feed the SDC339, having corrected this signal, and our power source began to work generating the Stanby signal , when placing the jumper between Power ON and GND, our source started without problems. The problem in this source was caused by the SDC7500 chip.
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.
Here I leave other links to different videos of repairs:
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