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Philips PM3208 - 4.4 Calibrator

Philips PM3208
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4-6
4
CIRCUIT
DESCRIPTION
4.3.2
CRT
contro!
The
CRT
has
several
electrodes.
~
The
filament,
pins
1
and
14,
is
supplied
with
6,3
V
(AC)
from
the
line-transformer.
-
The
cathode,
pin
2,
is
at
a
fixed
potential
of
—
2000
V.
-
G1,
pin
3,
has
already
been
described.
The
potential
is
about
—
2000
V.
Intensity
control
is
made
by
RV3033,
"INTENSITY".
-
G2,
an
anode,
pin
12,
is
at
a
fixed
potential
of
about
+100
V,
by
means
of
the
voltage-divider
R2016-2017.
—
G3,
pin
4,
has
already
been
described.
The
potential
is
about
—
700
V.
Focus
control
is
made
by
RV3035,
"FOCUS".
-
G4
and
G5,
pin
6,
are
used
for
astigmatism
control,
by
means
of
VR2018.
The
potential
can
be
adjusted
between
0
and
+160
V.
-
The
vertical
deflection
plates,
pins
7
and
9,
are
driven
by
the
vertical
output
amplifier,
as
already
described.
-
The
horizontal deflection
plates,
pins
11
and
13,
are
driven
by
the
horizontal
output
amplifier,
as
already
described.
-
The
trace
rotation
coil
L2001,
resistance
about
500
2,
has
been
placed
around
the
CRT
and
is
intended
to
align
the
trace
with
the
horizontal
graticule-lines.
The
current
through
the
coil
can
be
adjusted
between
—
8
and
+12
mA
by
means
of
RV3036,
"TRACE
ROTATION".
-
The
illumination
of
the
graticule
can
be
controlled
by
RV3037,
"SCALE
ILLUM".
4.3.3
HV
supply
The
~—
2000
V
high-voltage
for
the
CRT
is
made
by
means
of
a
DC-DC
converter
consisting
of
Q2001,
1C2001
and
the
transformer
T2001.
The
converter
is
supplied
with
about
+18
V.
Voltage
control
is
obtained
by
means
of
1C2001.
The
output
of
the
converter
is
a
sinusoidal
AC
voltage,
available
at
the
secondary
winding
of
T2001.
The
peak-value
of
this
voltage
is
about
1000
V.
The
voltage
is
rectified
and
multiplied
by
voltage-doubler
C2013-D2011-D2010-C2011
and
smoothed
with
C2013.
4.4
CALIBRATOR
In
the
calibrator
circuit,
a
square-wave
voltage
for
checking
purposes
is
produced.
Frequency
of
the
square-wave
is
about
1
kHz.
The
pulse
duty-cycle
is
50
%
and
the
peak
to
peak
amplitude
1
V.
The
square-wave
is
generated
in
a
free-running
multivibrator,
consisting
of
two
gates
of
1C4001,
pins
4
and
3.
The
other
two
gates,
pins
11
and
10,
are
for
pulse-shaping.
Via
the
voltage
divider
R4010-4011-4012
the
signal
is
fed
to
the
probe
adjustment
output
terminal
at
the
front
of
the
instrument.
4.4
CALIBRATOR

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