The most common fault will usually be related to data storage. The Dell Company does not make its own hard drives, so it uses other companies already made HDD. As already mentioned on this site, the more data that is packed in modern hard drives, the more chance it will fail. Especially SATA hard drives, and the perpendicular method writing data to the disk make the hard drives the number one component that fails first.
There are many factors that influence hard drive health. From hard drive temperature to the power that it gets from the power supply. Also vibration, heavy loads, etc. And, manufacturing quality is not in last place.
Motherboard capacitor problems. A well known issue with the motherboard stability is due to low quality capacitors. Symptoms include not starting in the morning, failing to install OS, or performing slow. These problems can be diagnosed with an oscilloscope by connecting a probe to the “+” capacitor pin. If the voltage is not stable, then almost 100% of the time, this will be a capacitor fault. Almost always, the faulty capacitors will show a fault sign like a varied color cap or bumpy top or bottom.
MOSFETS. These are transistors that deal with high power to the motherboards. The most common place where the MOSFETS fail is due to the CPU step down voltage converter.
This can be quickly diagnosed by measuring the +12V rail that connects to the motherboard. If this shows a low resistance like 100 Ohms, we have one or more of the MOSFETs which are faulty. Sometimes, a faulty MOSFET will show itself like a burned element, and sometimes it is extremely hot and found by measuring all MOSFETs with a multimeter. In order to recognize a MOSFET, note that they almost always are accompanied in circuits by coils, and a coil like one in the image above is always next to a pair of MOSFETS. Most of the time, the MOSFETs work in pairs or groups of pairs. Like one pair we see here is accompanied with a few capacitors like in the picture below.
The CPU is very unlikely to fail. An exception would be when one MOSFET fails and when the CPU gets a high voltage. If we use a faulty CPU on a new motherboard, then the motherboard may also be damaged.
RAM faults. This is usually found on older systems, over 3 + years old. Sometimes, observed strange system behavior, or fails to install OS. And, sometimes there are almost no symptoms at all. This is because of the faulty RAM cell which is at 1700 MB which will be not noticeable until the computer uses more than 1700 MB of RAM.
Overheating. Basically, Dell desktops have good cooling systems. Except on some models where the South Bridge and North Bridge get extremely hot.
Software related issues. Usually, these are related to viruses and other malicious software. It is recommended to check hardware in the first place and then turn to the virus scan or software troubleshooting. The best virus removing tool to date is Malware Bytes. If the computer does not boot, try to boot it into a safe mode and install Malware Bytes.
A system restore point is also a good tool if nothing can remove the virus.
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