ROH 120 User manual
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Distribution Amplifier
Model 120
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The
Model
1
20,
distribution
amplifier, offers high performanceand estab-
1
ished
reliability
for
demanding
applications in commercial
communica-
tion service. Dual and four channel units are available in totally self-
contained 19 inch rack
mount
packagin
g.
These units incorporate the
lat
es
t developments in solid sta
te
technology,
combined
with
premium
co
mponents and rigorous construction detail. Internal assembly
is
modu-
lar and
may
be
se
rviced by the exchange
of
plug-in assemblies.
Each
channel includes a separate regulated
power
supply to enhance system
reliab
ility
and
minimize
channel crosstalk. Both test jacks and the gain
adjustments are provided on the front panel. The test jacks
ca
n
be
switched to either the
input
or
output
circuitry
for external test and level
m
eas
urement. An optional
VU
meter
is
available for
monitoring
the
input/output
levels
of
each channel. The meter sensitivity
is
switch
selected between
-20
and +
20
dB in 10 dB steps. The 0 dB calibration
can be adjusted
over
a 10 dB range to
include
the 0,
+4,
or
+8
dBm
standard references.
Meter
response balistics may be selected for stan-
dard
VU
characteristics
or
a peak respo
nding
indication,
which
will
indicate signal peaks
qui
ckly
without
overshoot
or
averaging. Termina-
tion
of
the
equipment
is
made to nonbreakable plastic barrier blocks.
Termina
ls
are
sc
rew compressed
wire
clamps
which
make a
sec
ure
connection
without
requiring
wire
lugging
or
wrapping. Power require-
ments are compatable
with
11
5/
230
Vac,
50
or
60
Hz
line sources.
1111
1111
11111111
roH corPoraT1on
II
11111111
II
101
TecHnOLOGY ParK1aTLanTa
norcross.
Ga
30011
(404)
449-0873
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Specifications
Gain:
Input:
Outputs:
Output
Level:
Output
Isolation:
Frequency Response:
Distortion,
THD
or
IM:
Noise:
Meter Range:
Meter Calibration:
Meter
Accuracy:
Meter Response:
Meter
Balistics:
Ambient
Temperature:
Power Requirement:
Size:
Weight
:
0
to
+
30 dB, potentiometer adjustment
10 K ohms balanced bridging
60 dB CMR
at
60
Hz
+
20
dBm
maximum
common
mode
input
Eight 600
ohm
source terminated differential outputs
±1% balance
to
equipment
common
+20
dBm
70 dB at 10
kHz
20
Hz
to 20
kHz
±.5 dB at rated
output
-
50
dB, %%
maximum
at rated
output
85 dB SIN ratio,
-65
dBm
residual
-20
to
+
20 dB in 10 dB steps
0,
+4
or
+8
dBm
for OdB
indication
±
3%
of
reading and ±
2%
of
range
20
Hz
to
20
kHz
±.5
dB
Standard
VU
or
Peak
Responding
0° to
+
50° C operating range
11
5/230 Vac, ±10%, 50 to 60 Hz, 50 watts
3.5
11
H
x
19
11
W X
13
11
D
1
o
lbs.
Model Number and Name
Model
122
Model
124
Options
01
Dual 1
x
8
Distribution
Amplifier
Quad
1
x
8
Distribution
Amplifier
Add
Input/Output
Metering
•
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MODEL
120
DISTRIBUTION
AMPLIFIER
OPERATORS
INSTRUCTIONS
Your
ROH
120
Series
distribution
amplifier
was
carefully
inspec
ted,
both
elec-
trically
and
mechanically before shipment.
It
should
be
physically
free
from
mars
or
scratches,
and
in
perfect
electrical
order
upon
receipt.
The
unit
should
be
carefully
inspected
for
damage
in
transit
and
if
any
damage
is
noted,
ROH
Corporation should
be
contacted immediately. This
unit
is
designed to
mount
in
an
EIA
standard,
19
inch width rack.
The
120
Series
amplifiers
may
be
powered
from
either
115
or
230
V
ac,
50
or
60
Hertz. Before connecting the
120
to
an
ac
power
source,
verify
that
the
voltage
selector
switch
on
the
rear
panel matches
that
being used. A
pilot
lamp
on
the
front
panel
will
glow
when
power
is
applied
to
the
unit.
Input
and
output
connections
are
made
on
the
rear
panel terminal blocks.
There
is
a
separate
terminal block
for
each channel,
and
the individual
ter-
minals
are
clearly
labeled.
Separate gain adjustment
for
each channel
is
pro-
vided
by
potentiometers
located
on
the
front
panel. These
may
be
adjusted
after
removing the screw-on cap.
The
front
panel
test
jacks
for
each channel
may
be
switched
to
either
the
input
or
output
circuitry
for
external
test
or level
measurements . This
is
accomplished
by
pulling
out
the switch,
and
then
moving
it
to
either
the
input
or output
position.
A
phone
jack
is
also
provided for
listening
to the
input/output
signal
selected
by
the switches. A
detailed
schematic
and
parts
list
for
the
distribution
amplifier
is
attached.
If
the meter option
is
ordered,
the
front
panel switches
also
sele
ct
which
input or
output
is
to
be
measured
by
the meter
circuit.
The
meter range
and
response
are
selected
with
interlocking
pushbutton switches.
When
the
INPUT
/
OUTPUT
switch
is
in
its
center
position,
the
test
jacks provide
an
external
input to the meter
circuit.
If
the meter option
is
ordered, see the
attached
pages
for
more
detailed
information
on
the meter
circuit.
Unless otherwise
requested, the meter
circuit
is
factory
calibrated
to
read O
VU
for a O
dBm
level .
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MODEL
120
1120
DISTRIBUTION
AMPL
I
FIER
MODULE
PARTS
LIST
Item
Description
Part
Number
or
Type
Manufacturer
Cl,4 3.3 uf/35 V
tant
T392C335K035AS
K
emet
C2,5
0.03 uf/100 V cera
TG-S30
Sprague
C3,6
560
uf/30 V
elec
TCG
561U030GlL3P
Mallory
C7
,8,
10
0.001 uf/250 V cera
2SSD10
Sprague
C9
l uf/50 V cera
CZ5Ul05
Sprague
Cll,12
33
uf/16 V
tant
T392D336K016AS
Kemet
Dl-4 l
A/50
V
Si
1N4002
Motorola
Fl,2 1/2
A/250
V
MDL
Bussman
L
l,
2
1000
uH
10
%
50
mA
RFC-S-1000
Nytronics
Rl-4,
14-21
4.99 k
ohms
1/4 W1%
RN55D
Allen Bradley
RS,6,7 20.0 k
ohms
1/4 W1%
RN55D
Allen Bradley
R8
1 k
ohms
1/2 W
10
%
3389P
Bourns
R9
20.5 k
ohms
1/4 W1%
RN55D
Allen Bradley
RlO
100
k
ohms
1/4 W5%
RCR07
Allen Bradley
Rll
1 k
ohms
1/4 W5%
RCR07
A
11
en
Bradley
Rl2,30-45 10.0 k
ohms
1/4 W1%
RN55D
Allen Bradley
Rl3
5.
1 k
ohms
1/4 W5%
RCR07
Allen Bradley
R22-29
10
k
ohms
1/4 W1%
RN55D
Allen Bradley -
R46-61
301
ohms
1/4 W1%
RN55D
Allen Bradley
Ul
-18 V Regulator
MC7918
CP
Motorola
U2
+18
V Regulator
MC7818
CP
Motorola
CHASSIS
PARTS
LIST
Item Description
Part
Number
or
Type
Manufacturer
1
LED
FLV
540
Fairchild
2 Input/Output Switch
Type
7203
C &K
3 Potentiometer
CM
40333
Claros
tat
4 Test Point (Black) l05-0803-001 E.F. Johnson
5 Test Point (Green) 105-0804-001 E.F. Johnson
6 Test Point
(Red)
105-0802-001
E.
F.
Johnson
7 1.5 A
Circuit
Breaker
815175
Li
ttl
efuse
8 Voltage Switch
46256LFR
Switchcraft
9
AC
Line
Cord
Receptacle
EAC-203
Switchcraft
10
Transformer
354
T
riad
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1001
METER
ASSEMBLY
TECHNICAL
DESCRIPTION
The
m
eter
ass
emb
ly includes the
amplifier
c
ircuitry,
the meter
mo
vement, the
met
er
lamps
and
the ganged pushbutton panel switch.
The
amplifier
provides
up
to four
balanced bridging inputs
which
are
isolated
and
produce nominal
line
loading. T
he
number
of inputs used depends
on
the r
eq
uirements of the instrument with
which
the
meter
is
asso
ci
ated.
The
inputs
are
isolated
by
the
summing
amplifiers
UlA,B
wh
ich
combine
each
side
of the input
line.
The
differential
amplifier
UlD
converts the
balanced inputs to
an
unbalanced output to
drive
the range switch
and
remaining
circuitry.
Resistors
R16-20
in conjunction with the pushbutton range switch
for
m a
step
attenuator
prior
to the
circuit
voltage
amplifier
section
comprised of
UlC
and
U2A.
The
overall
voltage gain
is
adjusted
by
the
calibration
potentiometer
R23
which
provides a
10
dB
variation
in
circuit
sensitivity.
IC
amplifiers
U2D,C
driv
e
separate
full
wave
rectifier
circuits
for
the
RMS
and
peak
response
functions.
The
meter
movement
is
switched between the
two
circuits
depending
on
the
desired
response.
An
additional
amplifier
U2B
is
employed
to
accelerate
the meter point
er
travel
in the peak response
mode.
Capacitor
C6
and
resistor
R38
and
the meter
coil
are
enclosed in the feedback loop
of
U2B
which helps overcome the response delay
caused
by
the mechanical
inertia
of
the meter
movement.
PARTS
LIST
Item Description
Part
Number
or
Type
Manufactur
er
Cl,2 0. 1
uF
16
V cera
HY-450
Sprague
C3
0.001
uF
250
V cera 2SS-Dl0 Sprague
C4
l.
5
uF
50
V
7CZ5Ul5508
Sprague
C5
33
uF
16
V
tant
T392D336K016AS
Kemet
C6
330
uF
6.3 V
T392F337K006AS
Kemet
01-4
100
mA
50
V
Ge
lN270
ITT
-
Il ,2
55
V 0.05 A
1835
Chicago Miniature
M Meter 13-1001
ROH
Rl-8,17 30. 1 k
ohms
1/4 W1%
RN55D
Allen Bradley
R9-
l4
10
k
ohms
1/4 W1%
RN55D
Allen Bradley
Rl5
100
ohms
1/4 W5%
RCR07
Allen Bradley
Rl6
100
k
ohms
1/4 W1%
RN55D
Allen Bradley
Rl8
9090
ohms
1/4 W1%
RN550
Allen Bradley
Rl9
2150
ohms
1/4 W1%
RN550
Allen Bradley
R20,21,26
1000
ohms
l/4
W1%
RN550
Allen Bradley
R22,27
11
k
ohms
1/4 W1%
RN550
Allen Bradl
ey
R23,32
10
k
ohms
1/2 W
10
% 3389-103
Bourns
R24
2.4 k
ohms
1/4 W5%
RCR07
Allen Bradley
R25
51
k
ohms
1/4 W5%
RCR07
Allen Bradley
R28
5.
1 k
ohms
1/4 W5%
RCR07
Allen Bradley
R29,30
24
k
ohms
1/4 W5%
RCR07
Allen Bradley
R31,33
7.5
k
ohms
1/4 W5%
RCR07
Allen Bradl
ey
R34,35
10
k
ohms
1/4 W5%
RCR07
Allen Bradley
R36
1 k
ohms
1/4 W5%
RCR07
Allen Bradley
R37
1 k
ohms
l/2
W
10
% 3389-102
Bourns
R38
200
ohms
1/4 W1%
RN55D
Allen Bradley
Sl
4PDT
7
position
switch
PB15
CRL
•
Ul, 2
Integrated
Circuit
TL075CN
or
RC4136N
Texas
Instru
me
r
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1001
METER
ASSEMBLY
CALIBRATION
PROCEDURE
Meter Zero Adjustment:
For
maximum
accuracy, the meter mechanical zero should
be
checked
periodically.
The
meter
is
properly
zero-set
when
the
pointer
rests
over the zero
calibration
mark
and
the
unit
is
in
its
normal
operating environ-
ment
and
is
turned
off.
If
it
is
necessary to
reset
the zero, proceed as follows:
Turn
the ac
power
off
and
wait
one
minute
for
all
capacitors
to discharge. Rotate
the zero adjustment screw clockwise
so
that
the
pointer
is
left
of zero
and
moving
upscale. Continue
to
rotate
screw clockwise
until
the
pointer
is
exactly
at
zero.
Calibration
Adjustment: Potentiometer
R23
located
at
the top edge of the meter
amplifier
board
is
used to
calibrate
the meter assembly.
The
range of adjustme
nt
will
accommodate
0, +4,
and
+8
dBm
input
for
a O
dB
scale
indication.
A 1
kHz
test
frequency of
certified
amplitude should
be
used
for
the
calibration
adjust
m
ent.
Peak
Response Adjustment: Potentiometer
R37
located immediately below the
calibra-
tion
potentiometer
adjusts
damping
of
the meter
movement.
The
meter response
switch button should
be
in the
released
position.
Apply
a 1
kHz
test
frequency
to the instrument input
and
observe the
pointer
deflection.
The
meter
pointer
will advance
rapidly
to
the O
dB
scale
mark
with a
minimum
of
overshoot.
The
damping
should
be
adjusted
at
the O
dB
mark
with approximately
10
%
initial
overshoot.
The
return
to O
is
slow
and
requires
several seconds.
RMS(VU)
Tracking Adjustment:
The
remaining potentiometer
R32
on
the
circuit
board
adjusts
the
RMS
calibration
to
indicate
the
same
as the
peak
when
the response
button
is
depressed.
With
a continuous
input
signal the meter
indication
should
not change
when
the response button
is
depressed or
released.
After the above
performance
is
obtained the
calibration
potentiometer will simultaneously provide
the
overall
calibration
adjustment
for
both response
functions.
This manual suits for next models
2
