1 Precautions
1-1 Safety Precautions
WARNINGS2. Inspect all protective devices such as nonmetallic
1. For continued safety, do not attempt to modify thecontrol knobs, insulating materials, cabinet backs,
circuit board.adjustment and compartment covers or shields,
2. Disconnect the AC power before servicing.isolation resistor-capacitor networks, mechanical
insulators, etc.
3. When the chassis is operating, semiconductor
3. Leakage Current Hot Check (Figure 1-1):
heatsinks are potential shock hazards.
WARNING: Do not use an isolation transformer during
1-1-1 Servicing the High Voltage VR this test.
and CRT :Use a leakage current tester or a metering system
that complies with American National Standards
WARNING:A high voltage VR replaced in the wrong
Institute (ANSI C101.1, Leakage Current for
direction may cause excessive X-ray
Appliances), and Underwriters Laboratories (UL
emissions.
Publication UL1410, 59.7).
Caution: When replacing the high voltage
4. With the unit completely reassembled, plug the AC
adjustment VR, it must be fixed by a
line cord directly into a 120V AC outlet. With the
soldering iron after it is properly set.
unitOs AC switch first in the ON position and then
1. When servicing the high voltage system, remove
OFF, measure the current between a known earth
the static charge by connecting a 10 kohm resistor
ground (metal water pipe, conduit, etc.) and all
in series with an insulated wire (such as a test
exposed metal parts, including: metal cabinets,
probe) between the chassis and the anode lead.
screwheads and control shafts. The current
2. If the HV VR requires adjustment, (a) Replace themeasured should not exceed 0.5 milliamp. Reverse
VR and adjust the high voltage to the specification.the power-plug prongs in the AC outlet and repeat
(b) Use a soldering iron to melt the adjustment capthe test.
on the HV VR to prevent any movement.
(READING SHOULD
3. When troubleshooting a monitor with excessivelyNOT BE ABOVE 0.5mA)
HV, avoid being unnecessarily close to the monitor.
Do not operate the monitor for longer than isLEAKAGE
DEVICECURRENT
necessary to locate the cause of excessive voltage.UNDERTESTER
TEST
4. High voltage should always be kept at the ratedTEST ALL
EXPOSED METAL
value, no higher. Only when high voltage isSURFACES
excessive are X-rays capable of penetrating the shell
2-WIRE CORD
of the CRT, including the lead in glass material.
Operation at high voltages may also cause failure of
the CRT or high voltage circuitry.ALSO TEST WITH
PLUG REVERSED
5. When the HV regulator is operating properly, there(USING AC ADAPTERPLUG AS REQUIRED)EARTH
is no possibility of an X-ray problem. Make sure theGROUND
HV does not exceed its specified value and that it is
Figure 1-1. Leakage Current Test Circuit
regulating correctly.
6. The CRT is especially designed to prohibit 1-1-4 Product Safety Notices
X-ray emissions. To ensure continued X-ray
Some electrical and mechanical parts have special
protection, replace the CRT only with one that is
safety-related characteristics which are often not
the same or equivalent type as the original.
evident from visual inspection. The protection they give
7. Handle the CRT only when wearing shatterproof
may not be obtained by replacing them with
goggles and after completely discharging the highcomponents rated for higher voltage, wattage, etc. Parts
voltage anode.that have special safety characteristics are identified by
8. Do not lift the CRT by the neck.!on schematics and parts lists. A substitute
replacement that does not have the same safety
1-1-2 Fire and Shock Hazard :characteristics as the recommended replacement part
Before returning the monitor to the user, perform themight create shock, fire and / or other hazards. Product
following safety checks:safety is under review continuously and new
instructions are issued whenever appropriate.
1. Inspect each lead dress to make certain that the
leads are not pinched or that hardware is notComponents identified by on schematics and parts
lodged between the chassis and other metal parts inlists must be sealed by a soldering iron after
the monitor.replacement and adjustment.
CHB5**7L/6**7L/7**7L1-1 |
ACEC
