Medion B1997PNST Manuel de service télécharger pdf (Page 4)

PrecautionsPage 2

MD 1998LE (B1997PNST)

1 Precautions

Please follow these safety and servicing precautions to prevent damage and to protect against potential

hazards such as electrical shock and X-rays.

1-1 Safety Precautions

1-1-1 Warnings

1. For safety purpose, do not attempt to modify

the circuit board, and always disconnect the AC

power before performing servicing on the

monitor.

2. Operation of the monitor outside its cabinet or

with the cover removed involves the risk of

shock hazard. Repair work on the monitor

should only be attempted by service personnel

who are thoroughly familiar with all necessary

safety precautions and procedures for working

on high voltage equipment.

3. Do not lift the CRT by the neck. After

completely discharging the high voltage anode,

handle the CRT only when wearing shatterproof

goggles. Try to keep the CRT away from the

body during handling.

4. High voltage should always be kept at the rated

value, no higher. Only when high voltage is

excessive are X-rays capable of penetrating the

shell of the CRT. Operation at high voltages

may also cause failure of the CRT or high

voltage circuitry.

5. The CRT is especially constructed to limit X-

ray emission to 0.5mR/HR at 300 microamperes

anode current. To ensure continued X-ray

protection, replace the CRT with only the same

or equivalent type as the original, and adjust the

anode’s voltage to the designated maximum

rating, never to exceed.

1-1-2 Safety Checks

Before returning the monitor to the user, perform

the following safety checks:

1. Inspect to make certain that each lead dress is

not pinched or that hardware is not lodged

between the chassis and other metal parts in

the monitor.

2. Inspect all protective devices such as

nonmetallic control knobs, insulating materials,

cabinet backs, adjustment and compartment

covers or shields, isolation resistor-capacitor

networks, mechanical insulators, etc.

3. AC Leakage Current Check

Always perform the AC Leakage Current

Check on the exposed metal parts, including

metal cabinets, screwheads and control shafts,

as follows:

a) Plug the AC line cord directly into a rated

AC outlet. Do not use an isolation

transformer during the check.

b) Use an AC voltmeter with at least 5000

ohms per volt sensitivity as follows:

Connect a 1500 ohms, 10 watt resistor

paralleled by a 0.15uF AC capacitor in series

with all exposed metal cabinet parts and a

known earth ground, such as electrical

conduct or electrical ground connected to

earth ground, as shown in the Figure 1-1.

Measure the AC voltage across the

combination of resistor and capacitor.

c) Reverse the AC plug at the AC outlet and

repeat the steps for AC voltage

measurements for each exposed metal part.

d) Voltage reading must not exceed 0.3 volts

RMS, equivalent to 0.2 milliampere AC. Any

value exceeding this limit ill constitute a

potential shock hazard and must be

corrected immediately.

Figure 1-1. Set Up For AC Leakage Current Check

To kn ow n

earth ground

1500 ohm 10 watt

0.15ufd

To exposed metal

cabinet part

1 2 3 4 5 6 7 8 9 ... 26 27

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Medion B1997PNST Manuel de service Page 4

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