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SAFETY PRECAUTIONS
General
Guidelines
1. It is
advisable
to
insert
an
isolation
transformer
in the AC
power
line before servicing a hot chassis.
2.
When servicing, observe the original lead dress, especially
the
lead dress
in
the
high voltage circuits.
If
a short
circuit
is found, replace
all
parts which have been overheated
or
damaged
by the short circuit.
3.
After servicing, see to it that all the protective
devices
such
as
insulation barriers, insulation papers, Shields, and
isolation R-C combinations,
are properly
installed:
4. Before
switching
the power
on,
measure the resistance
between B+ line
and cold side chassis ground. Connect
the"-" side of an ohmmeter
to
the B+
line,
and the"+" side
to chassis ground.
Each
line must
have
more
resistance
value than the specified one
as follows:
B+
Line
Minimum
Resistance
210V (TPP1)
10 kQ
210V
(TPP2)
10
kn
41V (TPP3)
3kQ
15V (A6 pin 1)
5kn
12V (IC503
pin 3)
500
the
AC power cord plug
from
the
AC
line outlet.
6. High voltage points, as high as 31.5±0.3kV, are present
when the set
is in operation. Operating the set
without the
rear
cover
involves
in a dangerous electrical shock from
the set power supply. Servicing must not be attempted by
anyone
who
is
not
thoroughly
familiar
with
the
necessary
precautions when working
on
high voltage equipment.
Always
discharge the
anode
of the
picture tube to
chassis
ground before
handling the picture tube.
7. After
servicing, make the following leakage current checks
to prevent the customer from getting a dangerous electrical
shock.
Leakage
Current
Cold Check
1.
Unplug the AC
power
cord
and short between the two
prongs of the AC plug with a jumper wire.
2. Set the power switch of this set to ON position.
3.
Measure the resistance value
with
an
ohmmeter
between
the
shorted
AC plug and each
exposed
metallic part
of the
set cabinet
such
as screwheads, connectors, and control
shafts. When the exposed metallic part
has
a
return path
to the chassis, the reading should be more than 1 Mn.
When the exposed metal part
does
not have a return
path
to the
chassis,
the
reading must be
infinity.
-r
OT-M3050W
Leakage
Current
Hot Check
(See
Fig.
2-1)
1. Plug
the
AC power cord directly
into
the
AC line
outlet.
Do
not
use an isolation transformer for
this
check.
2. Connect a
1.Skn 1
0 watt resistor in parallel
with
a 0.15pf
capacitor between each exposed
metallic
part of
the set
and
an
earth ground such as
a water pipe.
3. Use a high impedance AC voltage meter to measure
the
voltage across the resistor.
4. Measure the voltage at each
exposed
metallic part.
5.
Reverse
the
AC plug
inserting direction
at the AC line
outlet and repeat
each
of
the above measurements.
6. The voltage at any point
mast
be
less
than
0.75Vrms.
7. A leakage current tester (Simpson Model 229 or the
equivalent) may
be
used
to make
the hot checks. In this
case,
the
current
must
be
less than
S00µA.
8.
If the reading
is
more
than
the
above value, the set must
be repaired and rechecked
before
it
is returned
to the
customer because of a possibility of an electrical shock.
HOT· CHECK
CIRCUIT
To exposecl
metallic
parts
X-Radiation
WARNING:
Fig.
2-1
Water pipe
{ground)
1.
The potential
so1-1rces of X-Radiation
in
the monitor set
are the high voltage section and picture tube.
2. When
using
a picture tube
test
jig for service, make
sure
that the jig is capable
of
handling
35.0kV
without
causing
X-Radiation.
3.
For continued X-Radiation protection,
in
case
that
at least
one of the components listed below is replaced, follow the
adjustment procedure of
the high
voltage circuit.
Precise
adjustment is necessary for R547,
R562, and
A587 to
protect
X-Radiation.
Refer
to
"High
Voltage and
X-
Radiation Protective Circuit Adjustment section'.
T552 IC503 IC504 IC505 D531 R531 R547 R548
R562 R565 A575 R5n R578 R579
A580
R581
R582 R585 R586 R587
R593 R595
R770 0513
0514 0515 0521
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3
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