Compaq MV7540, Service Manual

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HP MV7540
6
2. Precautions And Notices
2-1 Safety Precautions
1. Observe all caution and safety related notes located inside the display cabinet.
2. Operation of the display with the cover removed, may cause a serious shock hazard from the display
power supply. Work on the display should not be attempted by anyone who is not thoroughly familiar
with precautions necessary when working on high voltage equipment.
3. Do not install, remove or handle the picture tube in any manner unless shatter-proof goggles are worn.
People who are not so equipped should be kept away while handling picture tube. Keep picture tube
away from the body while handling.
4. The picture tube is constructed to limit X-RAY radiation to 0.5 mR/HR. For continued protection, use the
designated replacement tube only, and adjust the voltages so that the designated maximum rating at the
anode will not be exceeded.
5. Symbol“ “ means safety relative parts. The use of substitute replacement parts which do not have
the same characteristics as specified in the parts list may create shock, fire or explode etc.
6. Symbol
“ ”
means X-ray relative parts. Before replacing any of these components please read the
parts list in this manual carefully to avoid creating higher anode voltage or x-ray. Especially for sealed
controls, such as VR902 and FBT screen VR etc, which were sealed by the manufacturer once their
optimum position has been set, please don’t dismantle them as your likes, otherwise you will break or
damage the component. If you need replace the parts with sealed control, please adjust the relative VR
to make sure the B+ voltage about 66.0V and well seal it with A+B glue or equivalent, which you can not
move away with one screw driver
7. Before returning a serviced display to the customer, a thorough safety test must be performed to verify
that the display is safe to operate without danger or shock. Always perform an AC leakage current
check on the exposed metallic parts of the cabinet, such as screw heads.
Test method for current leakage is described as follow.
(a) Plug the AC line cord directly into rated AC outlet (do not use a line isolation transformer during this
check).
(b) Use an AC voltmeter having 5000 ohms per volt or with more sensitivity in the following manner:
Connect a 1500 ohms 10 Watt resistor, paralleled by a 0.15UF, AC type capacitor between a
known good earth ground (water pipe, conduit, etc.) and the exposed metallic parts simultaneously.
Measure the AC voltage across the combination of 1500 ohms resistor and 0.15UF capacitor.
(c) Reverse the AC plug at the AC outlet and repeat AC voltage measurements for each exposed
metallic part.
(d) Voltage measured must not exceed 0.5 volts RMS. This corresponds to 0.35 milliamp AC. Any
value exceeding this limit constitutes a potential shock hazard and must be corrected immediately.
2-2 Product Safety Notice
Many electrical and mechanical parts in this chassis have special safety visual inspections and the protection
afforded by them cannot necessarily be obtained by using replacement components rated for higher voltage,
wattage, etc. Before replacing any of these components read the parts list in this manual carefully. The use
of substitute replacement parts which do not have the same safety characteristics as specified in the parts
list may create shock, fire, X-RAY radiation or other hazards.
2-3 Service Notes
1.
When replacing parts or circuit boards, clamp the lead wires around terminals before soldering.
2. When replacing a high wattage resistor (more than 1/2W of metal oxide film resistor) in circuit board,
keep the resistor about 10mm (1/2 in) away from circuit board.
3. Keep wires away from high voltage or high temperature components.
4. Keep wires in their original position so as to reduce interference.