Advertisement
DESCRIPTION
General
Electric Test Amplifier
Model
4EX16A1O
uses a single Integrated Circuit
module
for operation as a high
impedance
m
amp
Ii
f
ier .
lYhen
used
wi
t
h
RF Probe
19C3
1137OG1,
the Test Amplifier can be
corl-
nected to Test Set
Models
4EX3A1O
& 11 (or
a
standard multimeter) to function as a high-
sensitivity
RF
voltmeter.
The
amplifier
and probe
are
designed
for
measuring
the gain of receiver front
end
and
IF circuitsr
oscillator
injection volt-
ages,
and
for
measuring
RF
leve1s in other
RF
circuits.
The
amplifier
may
also be
used
for amplifying low level audio signals.
OPERATION
All operating controls
and
the input
and
output binding posts are conveniently
Iocated on the front of the amplifier.
The
binding posts are
spaced
for
use
with a dual-
banana
plug if desired.
GAIN
SELECTOR
Gain
selector switch
SlOOl
selects
the
Xl (unity) ,
X10 and
X5O
amplif
ier
ranges,
and
also turns the
amplif
i.er on
and of
f
.
BAI"ANCE
Balance
potentiometer
R1OOZ
is
used to
set the
4EX3A1O
(or multimeter) on zero
be-
fore
maklng
measurements. with the Test set
and
RF
Probe connected
to the anplifier
and
the gain selector on
X5O,
R1O02
is
adjusted
for zera meter reading on the Test Set or
multimeter.
ATTEI\TUATOR
Attenuator
RlOOl
controls the input
level to the Test Amplifier.
To
obtain
actual gains of XI,
X10
or
XbO, Rl0O1
must
be turned fully clockwise to the
CALTBRATE
position.
References
to
symbol
numbers
mentioned
in the following text
may
be found on
the
appricable outline Diagrailr
schematic Dia-
gram
or Parts List (see Table of contents).
CIRCUIT ANALYSIS
TEST AMPLIFIER
The
basic amplifier circuit
consists
of Integrated Circuit
module
IC-I
and 8s-
LB I
_40978
sociated circuitry
mounted
on printed wiring
boards A1OO1.
IC-I is a high
performance,
operational amplifier
whose
gain is
con-
trolled by three
feedback
circuits.
The
feedback
circuits
are selected by
GAIN
switch
S10O1. Resistors
RB
and
R9
form the
Xl
(unity) feedback loop; resistors
R6
and
R7
form the
X10
feedback loop, and
R4
and
R5
form the
X50
feedback loop.
Instructlons
for setting potentiometers R5,
R7 and R9 are
contained in the
Maintenance
section of this
manual (see Tab1e
of Contents).
The
input is coupled through
ATTENUATOR
R1OOI
and
a voltage divider network (nf
and
R2)
to terminal 5 of the IC.
The
output is
taken from terminal 10
and
applied to
the
feedback loops and the output terminal.
Battery voltage (L4 volts) is applied to
the
IC through terminals 11 (+)
and
6 (-).
Terminal 4 connects to ground through
R3.
A small difference in potential called
the "offset" voltage is present at terminal
10
regardless of the input voltage applied
to IC-l.
This voltage can be cancelled
out
by
BAI"ANCE
potent
iometer
R1002
so that
the
Test Set or multimeter can be set on zeta.
Instructions for setting the
BAI"ANCE
control
are contained in the
OPERATION
section of
the
manual
as listed in the Table of
Con-
tents.
The amplif
ler
may
also be
used
f
or
8fi1-
plifying audio signals in the
DC
to
z0-kEz
range.
The
audio frequency
response
of
the
amplifier at the different gain levels is
shown
in Figure
1.
RF
PROBE
RF
Probe
19C31137OG1
is a highly
sen-
sitive,
uncalibrated probe for detecting
RF
s
ignals in the
5-MIIZ
to
500-MHz range
.
Point-contact diodes are used in the
probe
for better sensitivity.
A curve
showing
the frequency
response
of the probe is
shown
in Figure
2.
The
probe is terminated in a dual-ba-
nana
plug that connects to the Test Amplifier.
The probe may
also be
connected
directly to
a rc oscilloscope for checking
RF
levels.
As an aid to the
servi.ceman
in trouble-
shooting
RF
clrcuits,
a calibration
proc€-
dure is provided for calibrating the
RF
Probe (see Table of Contents).
TIAIilTENANCE
DISASSEMBLY
To disassemble the amplifier for s€r-
vicing,
remove
the two Phillips-head
screws
in the front of the
nameplate and
carefully
I
Advertisement
