B. Specifications
Input Impedance
Min.
Typ.
Max.
Units
4
5
Input Signal Level
Gain: Continuously
Adjustable: Input 5
Input 4
Output
Output Current
20
Ω
load
Output current limits
Dither current adjustable
Output drift at max. gain
During warm-up (30 min.)
vs. temperature
vs. time (after 30 min.)
vs. supply voltage
4.95
49.5
–100
2
0.20
20
–20
3
Frequency Response
DC - 300 Hz max.
gain full load
Single ended with respect to common
5
50
0
200
5.05
50.5
+100
20
2
400
500
100
30
1
10
1
–3
K
Ω
K
Ω
V-peak
Amps/volt
Amps/volt
MA
MA
MAp-p
MA
MA/
_
F
MA/24 hrs.
MA
DB
Regulated Output
Supply into 500 Ohm load
Pin 7 to common
Pin 8 to common
Temperature Range
Operating
Storage
Power Supply Req’mnt
Voltage Range
+9
–9
–29
–40
+14
–14
+10
–10
+19
–19
+11
–11
+71
+85
+20
–20
Vdc
Vdc
_
C
_
C
Vdc
Vdc
Mechanical Specs
Module
Module Size
Module Weight
Controls
Special printed circuit card
5.0” x 3.5” x 1.0”
8 ox.
Screwdriver adjusted
Dither
Gain
Table 1. Electrical and Mechanical Specifications for the EM-A-10.
General
This manual is written primarily to establish a logical trouble-
shooting procedure for the solid state EM (electronic modular)
amplifier. Complete systems are beyond the scope of this manual
and will not be covered. Adequate information is presented for an
Electrical Technician to repair the EM-A-10 amplifier.
EM-A-10 (308118) Linear Servo Amplifier
A. Description
The EM-A-10 is a special purpose DC servo amplifier designed
specifically for a Vickers SE3 or SF4 flapper type servo valve.
The EM-A-10 consists of a high gain summing amplifier, a low
gain DC amplifier and a power output stage.
The amplifier module also contains a
10 volt regulated power
supply which may be used for development of input signals
through an external 5000 ohm potentiometer.
The complete amplifier and power supply are contained on a
plug-in module whose approximate dimensions are 3-1/2 x 5
inches. Refer to table 1 for electrical and mechanical
specifications.
C. Installation
The EM-A-10 servo amplifier is designed for mounting
on a power supply plate such as the EMP-A-11. Input
and output connections to the amplifier circuitry are
provided by printed circuit pin connections on the
module. These pin connections, when installed into a
plug-in receptacle, must be connected as shown in Table
2. TB2 wiring interconnections, located on the EMP-A-11
power supply plate, are shown for convenience.
Portions of the EM–A-10 servo amplifier are of the
incapsulated construction and must be replaced as
complete assemblies. Amplifier A1 and A2 shown on the
schematic diagram Figure 1 are examples of this type of
construction. Replacement of A1 and A2 require factory
adjustments to be performed to the resistance values
designated by an asterisk (*). Therefore, should
replacement of either amplifier be required, it is
recommended that the installation be accomplished by
Vickers. Replacement EM-A-10 amplifiers are available.
EMP-A-11
TB2
(J)A
(J)B
(J)C
Plug-in
receptacle
pin
conn’tions
Plug-in
module
pin
conn’tions
Signal
–
–
–
4
5
6
7
8
–
–
1
2
–
–
3
a
b
c
d
e
f
h
j
k
l
m
n
p
r
s
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Dither (13 Vac)
N.C
–19 Vdc input
Input #1
Input #2
Summing Junction
RegDC output
Regulated –DC output
N.C.
N.C.
Negative output to coil
Positive output to coil
+19 Vdc input
Slotted for polarizing
key
Common
Table 2. The EM-A-10 Plug-in Receptacle and
Terminal Board Interconnecting Wiring
D. Circuit Description
Amplifier Section - The EM-A-10 is a DC amplifier,
consisting of a high gain summing pre-amplifier feeding a
unity gain buffer amplifier which drives a power output
stage.
The output stage is statically adjusted to produce 200
Milliamperes (MA) of current through the 20
Ω
servo
valve coil. (Vickers type SE3/SF4 servo valve) and varies
from this 200 MA value with variations in input signal.
An explanation of the circuitry follows: Refer to the
pictorial diagram, Figure 1, the simplified schematic
diagram Figure 2, and the complete schematic diagram
schematic diagram Figure 3.
