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DT-M3050W
High Voltage and X-Radiation Protective
Circuit Adiustment
1,
Equipment to
be
used
•
High-voltage
meter (Measurable 50kV)
•
Programmable video generator
• Digital
voltmeter
• Jumper wire
2. lnitlal
Condition
PICTURE NORMAL button ..........
Picture full
SCAN SIZE button ••
••••••• .. •••
••••••
••••
Over
EHT ADJ VR
(R547)
•••••••••••••••••••
..
Center
X-RAY PROTECT
1
VA (R562) ... Center
X-RAY
PROTECT
2
VR
(R587)
... Minimum
(Counterclockwise fully)
3. Adjustment Procedure
(1) Set the input switches to LINE A.
(2)
Input
a cross
hatch pattern
signal
(fh"'33.
75kHz)
to
LINE
A and
short
between
the both ends
of R874
with
a jumper wire.
(3) Switch off
the main
power switch.
(4)
Connect
a
high-voltage
meter to the
anode
for
picture
tube.
(5)
Connect
a digital voltmeter
between
TPA14 and
GND.
{6)
Switch on
the
main
power
switch,
(7)
Adjust slowly
EHT
ADJ VR
(R547 on
C-P.C. Board} so
tha1
the
read:r:g
cf
the high-voltage
meter can be
34.0±0.1
kV
(8) Adjust
X-RAY PROTECT 1
VR (R562 on A-P.C.
Board} so
that
the
reading
of
the digital voltmeter
can
be 10.5±0.0SV.
(9)
Turn
slowly
X-RAY
PROTECT 2 VR
(R587
on C-P.C.
Board)
clockwise
until the set
shuts
down.
(1
O)
Turn slowly
EHT
ADJ VR
(R547)
approximately 45
degrees counterclockwise from the center position.
(11) Switch off the power ~witch of the set,
and
switch i1 on
again.
(12) Adjust
EHT ADJ
VR (R547) so that
the reading of the
high-voltage meter
can
be 33.5+0.1/-0kV.
During this, make sure that the set does not shut down.
(13) Adjust EHT
ADJ
VR (R547) so that the readit,g of the
high-voltage meter
can
be 34.0+0.1/·0.3kV.
At this time, make sure that the set shuts down.
If
the set does not
function
properly during process
12
and 13, repeat process 7 through 13.
(14)
Turn
EHT
ADJ
VA (R547)
approximately
45 degrees
counterclockwise
from
the center
position.
( 15)
Switch
off
the power switch of
the
set and
switch
it
on
again.
After that,
input
a dot pattern signal
{fh"'33.
75kHz).
(16} Adjust
EHT
ADJ VR (R547) so that
the
reading of the
high-voltage meter
can
be 31.5±0.2kV.
After
that,
remove
the jumper wire
shorting
R874.
(17) Connect the digital voltmeter between TPA11 and GND
and
make sure that the reading
is
93:tSV.
(18)
Change
the LINE
A
input signal from the
dot
pattern
signal
{fh=33.
75kHz}
to
a
reverse
cross
hatch pattern
signal (fh=33.75kHz).
(19} Adjust the CONTRAST control all the way up.
(20) Make sure that the reading of the high-voltage meter is
31.5
:t0.3kV.
After
that,
change
the
input
signal
from
the reverse
cross
hatch pattern signal to the cross hatch pattern
signal.
(21) Short between TPA 14 and GN
D
with the jumper wire.
(22)
Make
sure
that
the set
shuts
down.
(23}
Remove the jumper
wire.
(24}
Cover the three VRs: EHT ADJ VR
(R547}
and X-RAY
PROTECT
1 and 2 VRs
(R562,
R587)
with the sleeves
and
secure them in place with adhesive as shown
below.
NOTE:
It
is important
to
use an
accurate,
periodically calibrated
high-
voltage meter.
1. Input
the dot
pattern
signal
(fh=33.75kHz}
2.
Measure the high voltage. The meter (electrostatic type)
reading must be
31.5:t0.2kV.
If the reading
is
out
of
tolerance, immediate
service
and
correction
is
required to prevent the premature component
failure.
3. To
prevent an X-radiation,. it is
essential
to use the
specified
picture tube.
X-RADJATION PROT·ECTIVE CIRCUIT TESTS
These tests must be made as a final check before
the
set is returned to the customer.
1.
Equipment to
be used
• High-voltage meter
(Measurable
35kY)
•
Programmable video
generator
• Ampere meter
•
DC power
source
• Oscilloscope
• Digital voltmeter
•
7500 resistor (over 10w}
• Jumper wires
2. Preparation
-
4
-
(1) AC power supply
voltage
must be 120V AC.
(2} Input
the 33.
75kHz
reverse cross hatch pattern signal
to
LINE A.
33, 75kHz timing
chart
fd::37
.125MHz
fh=33. 75kHZ
fv"'59.947Hz (Interlaced
scanning)
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