3.2.3 CAUSES OF TROUBLESHOOTING IN THE VM

Malfunctions in VM arise, as well as in other products of electronic equipment for the following reasons:

As a rule, violations of soldering technology, assembly, flaws at the design stage, the use of poor-quality elements or incorrect replacement of elements with analogues (in the process of picking), as a rule, result from poor-quality manufacturing. Faults for these reasons usually appear in the first months of operation. The share of such VM from all received for repair is rather large and reaches 30%

VM comes to the user in most cases complete with a computer. When installing the complex on the desktop and when it is first turned on, as a rule, the user focuses on its convenient location and is in a hurry to become familiar with its capabilities and software, often forgetting to at least look at the technical descriptions, where there are always recommendations for using VM

You must also follow the rules for connecting the VM to the power supply circuits. All connections of the signal cables and the power connector should be made with the power off and the switch positions on the VM and the computer "OFF".

Often the cause of a malfunction of the VM is a connection to a poor-quality electrical network, i.e. use of sockets with poor contact, since many VMs do not withstand the successive loss of power and the reappearance of the supply voltage in the network at intervals of 0.5 - 1 sec. This category also includes faults due to mechanical damage caused by the user.

This reason is common to all electronic equipment products operating under design conditions (specified in the technical specifications). Printed circuit boards and solder are subject to aging, especially in places of high temperature. As a rule, the time between failures for a VM is more than 10,000 hours, which corresponds to 3-5 years of work.

There is another reason for the occurrence of malfunctions in the VM - it is illiterately performed repair, when in the process of repair by unqualified personnel the elements are replaced by the selection of analogues or changes are made to the circuit diagram. Incorrectly performed work can lead further to additional malfunctions in the VM, which greatly complicates its final repair.

Typical problems with modern CRT monitors:

• Faulty power supply - occurs as a result of power surges in the mains and poor-quality power supply. Very often, a power supply failure causes damage to other monitor modules.
• Failure of the line scanner. Most often occurs due to the strong contamination of the monitor with dust and breakdown of high-voltage circuits and TDKS.
• Failure of the frame scanning unit. Mainly due to the violation of the temperature mode of operation of the power elements of the unit.
• The failure of the video signal forming and processing board is mainly due to aging of the elements and violation of the temperature mode of operation.
• Disturbance of a color rendition and geometrical distortions of the image. Such faults may occur due to malfunction of the deflecting system due to aging of the elements and the magnetization of the kinescope. Mostly occurs when shocks during transportation and the action of sources of electromagnetic radiation.