Reasons and solutions for charging the computer case

Many people have encountered a phenomenon that there is a slight contact inductance when the chassis is touched. Some friends often mistakenly think that the computer is "leakage" and thus embarrassed. In fact, this is a normal phenomenon. Let us analyze it below.

Analysis: There are two reasons for the chassis to be charged:

There are two places in the microcomputer with 220V AC power, one is on the main board power switch of the main unit; the other is inside the microcomputer power supply. The power to the chassis may be caused by a short circuit between the two parts and the chassis or a fault in the power supply.

It is from the inside of the microcomputer power supply. In order to prevent electromagnetic interference from the outside of the microcomputer, a filter circuit is installed in the input circuit of the power supply 220V. The filter circuit consists of two capacitors connected in series, and the midpoints of the two capacitors are directly connected to the power supply case. Therefore, the theoretical value of the chassis potential is 110V. This type of leak is measurable with a test pencil.

The short circuit caused by the first cause may cause a personal injury accident and should be immediately shut down for maintenance. However, the probability of this failure is small. Your computer will not be for this reason.

Leakage caused by the second cause is inevitable. Because the leakage current is very small, it will not cause harm to the human body, but it will form "hemp electricity"--that is, acupuncture-like clicks felt when the body comes into contact with the exposed parts of the chassis. Does not affect the normal operation of the microcomputer.

There are two reasons for the CMOS error at boot:

First, due to a problem on the CMOS battery or the power supply circuit, the battery cannot be powered to the CMOS RAM after the shutdown, resulting in the loss of data stored therein.

Second, there is a virus. When the virus is activated, it attacks the CMOS RAM and changes the data.

Handling: The most effective way to eliminate leakage is to install the protective earthing device in strict accordance with the electrical installation specifications (should be grounded). However, the general household power supply has no grounding wire, so it is difficult. An easy way to do this is to put "insulation" on the exposed area of ​​the chassis.

For CMOS data loss can be solved by replacing the battery and troubleshooting the CMOS power supply circuit. However, the circuits of various motherboards are different, and it is difficult to overhaul. It should be handled by experienced personnel. If you have a virus, you can use the latest version of anti-virus software to remove the virus.