BK Precision 1403A User Manual

CIRCUIT DE.SCRIPIION
FET Buffen
FET
buffer
Q114
serves
as a
high
input
impedanee, low output
impedanee
stage
be-
tween the sweep
generator
and the horizontal
final amplifier.
In sweep operation,
FET
Q
114
prevents
"loading"
of the RC
eharge time
eonstant ramp rate.
Horizontal Amplifien
The
horizontal
final amplifier
is
eomposed
of a two transistor
push-pull
output stage,
Ql15
and
Q116.
Horizontal
positioning
of the
traee is
provided
by
VR3
(
<>POS eontrol on
the front
panel)
as it
ehanges the dc bias
supplied to
the
base of
Q116.
The
gain
of the
horizorrtal final
amplifier is
preset
by internal
adjustment VR102, as
it sets the limit of
emitter eurrent available for
Ql15
and
Q116.
The
voltage
outputs
of
Q115
and
Q116
are
developed
aeross R149
and
R150 and applied
to
the horizontal
defleetion
plates
of the
CRT.
EXTERNAL
HORIZONTAL OPERATION
When
SWEEP RANGE
switeh
52
is set
fully
eloekwise
to the EXT
position,
the
sweep
generator
is disabled
and an external signal
applied
at the
EXT SYNC/HOR
INPUT
jaek
provides
horizontal
defleetion of
the CRT
beam.
This
mode
of operation is
often ealled
X-Y
operation,
as
the horizontal input
pro-
duees X-axis
(horizontal)
defleetion,
and the
vertieal input
produees
Y-axis
(vertical)
defleetion.
Refer to
Fig.
4 for
a simplified eireuit
diagram,
or to the sehematie diagram for full
eireuit details. In this mode
of operation,
switeh
32 entirely
diseonneets
the sweep
generator
from
Q114.
The SWEEP
VARI/EXT
GAIN eontrol, VR4, is
eonneeted
between
the
FIOR INPUT
jaek
and FET buffer
Q114.
VR4
beeomes the
Horizontal
Gain eontrol,
as it
determines
the level of signal
applied to
Ql14.
At
m axim
um
gain
(no
attenuation), the
hori
-
zontal
ehannel sensitivity
is about 300 mV
per
division.
V.R4 is
eonneeted to
provide
a
eon-
stant input impedanee
of 1 megohm.
Q114
presents
negligible
shunting impedanee, simi-
lar
to
Q102
in the vertieal
ehannel..
The
output
of
Ql14
is amplified
by the
horizontal
final amplifier,
Ql15
and
Ql16,
just
as
in
sweep operation, exeept
that the external
horizontal
signal
is
being
amplified
instead of
the sweep sawtooth
signal.
LOW
VOLTAGE POITBR SUPPLY
Refer
to
the sehematic
diagram
at the
rear
of
the manual
for eireuit details.
The
power
transformer
has two
primaries
whieh
may
be wired in
parallel
for
Ll?
VAC
operation, or
in
series
for 230 VAC operation.
Taps also
permit
wiring
for 100 VAC opera-
tion. Neon
lamp
Nl and
resistor R15?
are
eonneeted aeross a
100-volt segment of
the
primtrV,
eausing the
lamp to
light
whenever
POWER switeh
S106
is
ON.
A eenter-tapped
seeondary
winding
of
the
power
transform er
provides
power
supply
souree
voltages
of
25 volts and
160 volts rms.
Bridge reetifier D104
provides
full
wave
reetifieation, and
is
eonneeted
to
provide
both
positive
and negative de voltages.
C116 and
C
1 17
provide
filtering, and Zener
diode D105
regulates
the
positive
side of the
bridge to
+15
volts.
C119 and
C120
provide
filtering,
and Zener
diode
D106
regulates the
negative
side of the bridge to
-15
volts. In
addition,
the
raw de from the
negative
side
of the
reetifier
is
also
dropped through
Rl55 and
regulated to
-6
volts
by Zener diode
D109.
These
regulated
voltages
are the
rrelean
sup-
plies",
providing
low
noise
operation
of sensi-
tive,
high
gain
stages
in
the
vertieal
and
horizontal ehannels.
A
+170
volt
supply
provides
the operating
voltage for the
vertieal and
horizontal final
amplifiers.
Full wave
reetifier
diodes Dl02
and
D103
eonvert
the
160 volt
rms
output
(225
volt
peak)
of the
power
transformer to de,
whieh is
filtered by
C114
and
C115,
providing
approximately
+170
volts.
Y
*
IIIGH
VOLTAGE
SUPPTY
The
high
voltage supply
provides
aeeeler-
ation
voltage for the CRT
beam. The
high
r
voltage
is derived from
the
500 volt winding
of
10

BK Precision 1403A Specifications

General

Brand	BK Precision
Model	1403A
Category	Test Equipment
Language	English