Philips pm3232 - Cathode-Ray Tube Circuit

77
3.2.3.
CATHODE-RAY
TUBE CIRCUIT
3.2.3.I.
Adjustment
to display
time-bcise lines
1500
V
Use a
well-insulated screw-driver
to
protect
both
yourself and
the
circuitry.
3.2.3.1.1.
Time-base
(R801
R802, R553)
—
Turn potentiometers R801
and
R802
(Fig. 3.1
1.)
clockwise and
potentiometer
R553 (Fig.
3.12.)
anti
-clockwise
—
Turn INTENS potentiometer
RIO
clockwise
—
Set X
POSITION potentiometer R1 to its
mid-position and
depress
MAGN
switch
SKI
—
Set the
POSITION
potentiometers R1 1
and
R12
to their
mid-positions
—
Set
TIME/cm switch SK2 to
1 ms
--
Depress BEAM SELECTOR
switches
A SK14
and
B
SK15
—
Set AMPL
switches SK17
and SK18 to .1
V/cm;
there
should
be
a
display
of two
time-base
lines
—
See for
adjusting
with R801, R802
point
3. 2. 3.6.
3.2.
3. 1.2.
Time-base
stability (R553)
“
Depress
Y/\ switch
SK4,
+
switch SK8
,
AC
switch SK11
and
BEAM
SELECTOR
switch
A
SKI
4
—
Turn
potentiometer
R553
(Fig.
3.12.)
clockwise
until the
time-base
line
disappears
—
Depress
AUTO
switch
SK10.
A time-base
line must
become
visible.
If necessary,
readjust
potentiometer R553.
3.2.3.2. Trace rotation (R813)
—
Depress AUTO
switch SK10
and BEAM
SELECTOR
switch
A SK14
—
Set AC-O-DC
switch SKI
6
to
0
—
Centre
the time-base
line
by
means
of
POSITION
potentiometer R1
1
—
Check that the
time-base
line runs exactly in
parallel with the
horizontal lines of
the
graticule.
If necessary,
readjust
trace rotation
potentiometer R813
(Fig. 3.1
1.)
3.2.3.3. Beam
correction
-
Depress
AUTO
switch SK10
and
BEAM
SELECTOR
switches A SK14
and
B
SK15
—
Set AC-O-DC
switches SK16
and SK19 to 0
—
Position the
traces
symmetrically around the centre
of
the screen using
POSITION
potentiometers R1
1
and
R12
—
Adjust
INTENS
potentiometer
RIO for a low
brightness
—
Check that both
traces
are equally bright.
If necessary,
slacken screw
S
(Fig.
3.1
1.)
and rotate
magnet T
(Fig.
3.1
1.)
until both
traces have the same
brightness.
Then,
tighten screw S
without
disturbing
the
adjustment
3.2.3.4. Focus and
astigmatism
(R809, R804)
-
Depress AUTO
switch
SK10
and BEAM
SELECTOR
switches
A
SK14
and
B
SK15
—
Set
TIME/cm
switch
SK2
to .2
ms
and TIME/cm
potentiometer to
CAL
—
Set
AMPL
switches
SKI
7
and
SKI
8 to
.1 V and AMPL
potentiometers
R4 and R5
to CAL
—
Set
INTENS
potentiometer
RIO
for normal
brightness
—
Set
AC-O-DC
switches SK16
and
SK19
to DC
—
Apply
a
sine-wave
signal
of
400 mVp.p, 2
kHz,
to
Y
/\
input
socket
BU3
and
Y
0
input socket BU5
Use
an
insulated
screw-driver
—
Adjust
FOCUS
potentiometer R9 and
astigmatism
potentiometer R809
(Fig.
3.11.)
for
sharp,
well-defired
traces. Find
the setting that
gives the best result
for
both
channels.
—
Set
FOCUS
potentiometer
R9
in mid-stroke
position
and
check
for
sharp traces.
If
necessary select
a
different
value
for R804.