Panasonic DVC PRO Studio AJ-D950P Service Manual page 1270

GENERAL GUIDELINES
1. When servicing, observe the original lead dress. If a short
circuit is found, replace all parts which have been
overheated or damaged by the short circuit.
2. After servicing, see to it that all the protective devices such as
i n s u l a t i o n b a r r i e r s , i n s u l a t i o n p a p e r s s h i e l d s a r e
properly installed.
3. After servicing, make the following leakage current checks to
prevent the customer from being exposed to shock
hazards.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs on the plug.
2. Measure the resistance value, with an ohmmeter, between
the jumpered AC plug and each exposed metallic cabinet part
on the equipment such as screwheads, connectors, control
shafts, etc. When the exposed metallic part has a return path
to the chassis, the reading should be between 1M Ω and
5.2M Ω.
When the exposed metal does not have a return path to the
chassis, the reading must be ∞.
Hot-Check Circuit
AC VOLTMETER
0.15µF
TO
APPLIANCES
EXPOSED
METAL PARTS 1500Ω
LEAKAGE CURRENT HOT CHECK (See Figure 1.)
1. Plug the AC cord directly into the AC outlet.
Do not use an isolation transformer for this check.
2. Connect a 1.5k Ω, 10 W resistor, in parallel with a 0.15µF
capacitor, between each exposed metallic part on the set
and a good earth ground such as a water pipe, as shown in
Figure 1.
3. Use an AC voltmeter, with 1000 ohms/volt or more
sensitivity, to measure the potential across the resistor.
4. Check each exposed metallic part, and measure the
voltage at each point.
5. Reverse the AC plug in the AC outlet and repeat each of the
above measurements.
6. The potential at any point should not exceed 0.75 volts
RMS. A leakage current tester (Simpson Model 229
equivalent) may be used to make the hot checks, leakage
current must not exceed 1/2 milliamp. In case a measurement
is outside of the limits specified, there is a possibility of a shock
hazard, and the equipment should be repaired and rechecked
before it is returned to the customer.
SAFETY PRECAUTIONS
COLD
WATER PIPE
10W (EARTH GROUND)
Figure 1
ELECTROSTATICALLY SENSITIVE (ES) DEVICES
Some semiconductor (solid state) devices can be damaged
easily by static electricity. Such components commonly are called
Electrostatically Sensitive (ES) Devices. Examples of typical ES
devices are integrated circuits and some field-effect transistors
and semiconductor "chip" components. The following techniques
should be used to help reduce the incidence of component
damage caused by static electricity.
1. Immediately before handling any semiconductor component
or semiconductor-equipped assembly, drain off any
electrostatic charge on your body by touching a known earth
ground.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, which should be removed for
potential shock reasons prior to applying power to the unit
under test.
2. After removing an electrical assembly equipped with ES
devices, place the assembly on a conductive surface such as
alminum foil, to prevent electrostatic charge buildup or
exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder
ES devices.
4. Use only an anti-static solder removal device classified as
"anti-static" can generate electrical charges sufficient to
damage ES devices.
5. Do not use freon-propelled chemicals. These can generate
electrical charges sufficient to damage ES devices.
6. Do not remove a replacement ES device from its protective
package until immediately before you are ready to install it.
(most replacement ES devices are packaged with leads
electrically shorted together by conductive foam, alminum foil
or comparable conductive material).
7. Immediately before removing the protective material from the
leads of a replacement ES device, touch the protective
material to the chassis or circuit assembly into which the
device will be installed.
CAUTION: Be sure no power is applied to the chassis or
circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged
replacement ES devices. (Otherwise hamless motion such as
the brushing together of your clothes fabric or the lifting of your
foot from a carpeted floor can generate static electricity
sufficient to damage an ES device).
X-RADIATION
WARNING
1. The potential source of X-Radiation in EVF sets is the High
Voltage section and the picture tube.
2. When using a picture tube test jig for service, ensure that jig is
capable of handling 10kV without causing X-Radiation.
NOTE: It is important to use an accurate periodically calibrated high
voltage meter.
3. Measure the High Voltage. The meter (electric type) reading should
±
indicate 2.5kV, 0.15kV. If the meter indication is out of
tolerance, immediate service and correction is required to prevent
the possibility of premature component failure. To prevent an
X-Radiation possibility, it is essential to use the specified picture
tube.