Page 10 - Testing Electronic Components

between as dielectric. The external coating is always connected to the
Monitor and TV chassis ground by a spring arrangement around the CRT.

This high voltage filter capacitor has very low leakage. Before removing
a CRT, ensure that you discharge this capacitor in order to prevent shocks
or serious injuries.

6. High Voltage

Monitors and TV have sections that use very high DC voltages. The high
voltage is needed to be applied to the CRT to attract the electron beam to
the phosphor. This high voltage could be as low as 12,000 volt in a
monochrome Monitor or as high as 30,000 volt in large colour monitor.
Flyback Transformer is the part that is used to generate the high voltage.

The high voltage circuit inside a Monitor or TV can give you a dangerous
electric shock and causes you to jerk violently. You could cut yourself by
accidentally knocking on sharp chassis edges. Be familiar with the high
voltage circuits before you work on any high voltage equipment.

7. X-Radiation

An X-ray is a form of radiation produced when a beam of electrons
strikes some material at a relatively high speed. The only source of X-ray
in a modern Monitor or TV is from the CRT. Prolong exposure to X-ray
can be harmful. However, the CRT does not emit measurable X-ray if the
high voltage is at the high voltage adjustment value only. When high
voltage is excessive, then only X-ray is capable of penetrating the shell of
the CRT, including the lead in glass material.

Test the brightness and use a high voltage probe to monitor the high
voltage each time a Monitor or TV comes in for repair. When the
brightness is raised, usually the high voltage will go-down, and when

brightness is reduced the high voltage will go-up. When troubleshooting a
Monitor or TV with excessively high voltage, avoid being unnecessarily
close to the set. Do not operate the Monitor or TV for longer than it is
necessary to locate the cause of excessive voltage. To ensure continuous
X-ray protection, replace the CRT with one that is of same or equivalent
type as the original.

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