Radio Corporation Of America BN-2A User manual

STEAM POWERED RADIO.COM

STEAM POWERED RADIO.COM

STEAM POWERED RADIO.COM
~
•
•
I BROADCAST.
AUDIO
EQUIPMENT
~------------------
•
I
•
-
•
•
.
~
'
•
•
•
•
•
•
'
•
•
!
''
;~
=
•
•
•
•
•
INSTRUCTIONS
Type
BN-2A
Portable
Remote
Amplifier
(Ml-11230)
RAD
.
IQ
CORPORATION
OF
AMERICA
lt
~"~'~'
lu~
~
E R I N G P R O D U C T S
DEPARTMENT,
CAMDEN,
N.
J.
.
~-
•
•

STEAM POWERED RADIO.COM
t
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
I
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2
--
I
Figure 1
-Type
BN
-2
A Portable Re
mot
e A
mp
li
fi
er, panel cover r
emove
d
a,•
--
......
---·=-
7
e
IJ
·'
l
-··---
~

STEAM POWERED RADIO.COM
•
•
•
•
:(t
•
•
•
•
•
:
lt
•
•
•
•
•
•
•
•
llt
•
•
•
•
•
•
:(t
•
'
•
•
•
•
•
:(t
•
•
'
•
DESCRIPTION
Application
The Type
BN-2A
Portable Remote•Amplifier
(MI-
11230)
is
a high-fidelity
unit
for
a-m
and
f-m
broad-
cast audio applications.
It,
is
designed
to
amplify
low-
level signals
for
transmission over a telephone line
to
the
studio.
The
·amplifier provides complete pickup facili-
ties
for
programs remote
from
the studio such
as
sports
events,
street
programs, political and social meetings,
park concerts and similar gatherings.
It
may also
be
employed for semi-permanent installations such
as
in
department stores,
night
clubs and restaurants,
or
may
be
used in a small studio for regular
use
or
as standby
equipment.
Components
The .amplifier
is
a four-stage resistance-coupled
unit
including three preamplifiers
in
the
first
stage
for
separate microphone
or
turntable
inputs. A switch
is
provided to permit
switching
a
fourth
input
into
channel
three. Each·preamplifier has its own mixer. A master
. 3
gain control
is
provided
as
part
of
the three-stage pro-
gram
amplifier section.
Output
terminals on the
front
panel may be used
for
simultane-0usly feeding the signal
to
a public address amplifier and a telphone, line. The
public address
output
has its
own
balanced volume con-
trol. Cueing
and
monitoring facilities are provided. A
control permits switching the public address input
to
·•cue", "amplifier
output"
or
"off".
A meter with an
associated
switch
is
used for checking level to the line
and also
for
giving an indication of the condition of the
amplifying tubes. A switch
is
provided for controlling
the
amount
of
meter
illumination.
All electrical components in the amplifier
arc
pre-
cision made
with
close tolerances. Step-type attenuators
are used.
The
1620 tubes
ue
especially designed for
broadc:ut applications where a minimum
of
noise and
microphonics are required.
The
three preamplifier
tubes and the first program amplifier tube are shock-
mounted
to
insure low microphonics and maximum pro-
tection
from
vibrations which are
often
experienced
during
remote broadcasts.
TECHNICAL
DATA
Power
Required
.A.-C Oper11lion
117 volts,
SO
to
60
cps, 2 f
w•tts
D-C
Optralion
"A"
Supply-6.3
volts, 2.1
amperu
mu
.
"B"
Supply-271
volts, 10 milliamperes
Fuse
A-C
line, 1
amper,
Tube
Kit
(Ml-11269)
4
RCA
1620
2
RCA
6]7•
RCA
6XfGT
•1620·,
m•y
be
used in place
of
6J7's
Optional Tube
Kit
(Ml-11269-A)
6
RCA
6J7
1
RCA
6XlGT
Note:
6J7'•
m•y
be
substituted
for
RCA
1620's
when
maximum
uniformity
of
characterinic:1 and
minimum
o{
microphonics,
hum
snd
di1tortion
are
not
required.
Source Impedance
llO
or
;o
ohms
balanced.
:M•y
be
used
with
210-ohm
microphone,
on
I JO-ohm tap. May •lso
be
uxd
with
an
unb•lanced
source.
See
text.
ln
_put Impedance
Unloaded
transformer
Moxiinum
Input
Level
-)0
dbl1\
Mixing
High level, alter
prumpli6cr
ch•nncls
Load
Impedance
l00/600
ohms
Power
Output
+u
dbm
for
distortion
of
Jen
than
t.O'}"o
u
JO
10
I J,000 cps
Goin
92
db
( 1JO-ohm source
on
I JO-ohm
input
t-O
600--0hm
load)
Frequency Response
± I
db
from
) 0
co
I l ,000 cps
(lig
.
2)
Noise
Level
Single
channel,
gain
maximum:
-30
dbm
Si~gle
channel,
gain
68
db
(m•sccr gain control set
at
12, mixer
gain
control
set
at
16):
-12
dbm
.
This
corraponds
to
a signal-1.0-noise
ratio
of
70
db
at
rated
power
output.
Dimensions
and
Weight
Length-14
½ inches
Depth-9
½ inches
Height-IO
inchc,
Wcight-29
pounds
Panel
Slope
IO
degrees_

STEAM POWERED RADIO.COM
•
•
•
•
•
a
•
•
•
•
•
•
•
•
•
•
•
•
•
•
:
=
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
4
'
·2
(D
0
z 0
IJJ
(/)
z
-2
0
....
V
i,.---
""
a.
(/)
IJJ
S-8850911
a::
20
100
1,000
FREQUENCY
IN
CYCLES
PER
SECOND
10,000
Figure 2- Frequency response
Construction
The back and
bottom
cover
of
the amplifier
is
made
removable for
ease
of
servicing.
The
top
cover, which
is
also removable
for
replacement
of
tubes, has a
curying
strap which fits
into
a recess on the cover when not in
use.
If a screwdriver
is
not
available, a.coin may
be
·
used to loosen the twist-lock fasteners which hold the
covers in place.
Two
tube
sockets and a fuse clip are
provided on the
bottom
side
of
the top
for
carrying
spare tubes and a spare fuse.
Only
two
spare tubes are
,required
(6X5GT
and 1620
or
6J7).
The
amplifier
is
designed wit.h a sloping panel
for
maximum
ease
of
operation. A removable panel
cover
protects the
con-
trol knobs and meter. A protective cover, MI-11277,
is
available
as
an accessory for
transporting
the amplifier
during inclement weather or
to
preserve its appearance.
Power
Requirements
The power cord and plug
of
the·amplifier
is
intended
to
be
connected
to
an a-c power line
of
the voltage and
frequency specified
under
Technical Data.
When
de-
sired, an MI-11214
Battery
Box and MI-11255
Battery
Kit may
be
used
to
furnish power.
The
batteries
in
this
kit
are described under Battery Connections.
The
power
cord assembly
for
a-c line operation
is
supplied
with
the
amplifier, and the power
cord
assemi?ly
for
d-c opera-
tion
is
supplied
with
the
MI-11214
Battery
Box. Each
of
these power cords
i6
equipped
with
a 12-terminal plug
which mates
with
the power receptacle
on
the amplifier
chassis.
CIRCUIT
Input
The
input
circuit
to each
of
the three preamplifier
channels consists
of
a
transformer
(T-1,2,3)
normally
connected
for
operation
from
a
150-ohm
balanced
source.
Other
possible
input
connections are described
under Imtallation.
An
RCA
1620
(or
6J7)
connected
as
a triode
(V-1,2,3)
is
used in each
of
the three pre-
amplifier channels. Three step-type attenuators
(R-5,
11,17) marked
MIC-I,
MIC-2, MIC-3 & 4, which are
connected in the coupling circuits
to
the first program
amplifier stage, serve
as
the mixers
to
control the levels
in each
of
the preamplifier channels.
First
Stage
of
Program
Amplifier
An
RCA
1620
(or
6]7)
is
connected
as
a pentode
(V
-
4)
in the first
program
amplifier stage. The
MASTER gain
control
(R-37)
is
a step type attenuator
in
the coupling
circuit
between the· first and second
program
amplifier stages.
Negative
feedback
is
applied
Figure
3-Panel
and
top
covers
-
'

STEAM POWERED RADIO.COM
•
•
•
•
:
lt
•
•
•
•
•
:~
•
•
•
•
•
•
•
-
t
\t
•
•
•
•
•
•
•
.~
I
•
•
•
•
•
•
:
lt
•
•
•
from
this control
through
R-19
to
the grid
of
the first
program amplifier stage.
Second
and
Third
Stages
of
Program Amplifier
The
second and third stages
of
the program amplifier
section
use
RCA
6]7
tubes connected
as
pentodes
(V-5,
6).
These stages are resistance coupled. A fixed feed-
back loop which includes
R-2
8 and C-
11
is
connected
around the two stages. This feedback reduces instability
caused by variations in the tube characteristics, changes
in the
output
load and fluctuations in the supply volt-
age.
It
also reduces distortion and improves the fre-
quency response.
The
output
transformer
(T-4)
is
designed to operate
into a 500- to 600-ohm load. A 2-db pad
(R-43
, 44, 45,
46,
47)
in the
output
partially isolates the
output
stage
and the telephone line
so
that
this stage and the
output
meter work
into
a nearly
constant
impedance.
Meter
Circuit
A
VU
meter (
M-1)
is
mounted on the
front
panel
for measuring
the
output
level and voltages in the
cathode circuits
of
each
of
the amplifying tubes except
V-5. Metering
of
V-5
is
accomplished in its plate
circuit. A panel-mounted selector switch (S-5) per-
MIXERS
MASTER
5
rnits selection
of
the various readings. A
LIGHT
switch
(S-6) mounted in the upper right-hand section
of
the
panel permits either high.or
l!)w
illumination from the
meter lamps. If
it
should become necessary, checking
of
the tubes by the meter during a program
is
possible.
The
meter pad
(R
-5
2)
is
connected
so
chat the meter
will read
"O"
for an
output
level
of
+s vu or
+s
dbm.
Termin
a
ls
are provided on the pad
so
that
it
may
be
reconnected
for
other
desired meter calibrations (
see
Installation).
In
terference Elimination
The amplifier has been especially designed to eliminate
stray
r-f
and a-c power line pick-,up. For this purpose
the transformers are electrostatically shielded, and
capacitors C-21 and C-
22
in the
output
circ.uit bypass
radio frequencies
to
ground.
Rectifier
The
self-contained rectifier comprises a power trans-
former
(T-5)
a one-ampere fuse
(F-1)
an RCA
6X5GT
full-wave rectifier tube
(V-7)
and a resistance-capacity
filter. A small d-c voltage
is
tapped off the voltage
divider
circuit
comprising
R-50
and R-51 for heater
bias
of the amplifier tubes.
•
MIC- I
20-208
STEPS
20
-
208
STEPS
I
'-
------
PR~------<
c'
A A
MIC-2
[
;-
- -
----
-
PRE'>------1
20
-
200
STEPS
A
f-------<PGIM>--+---i
MIC- 3
[
)--
-
,...
I
\..
--
-o
V
MIC
- 4
TO
AMPLIFIERS
I
I
'-----'
20-208
STEPS
A
3 STAGES
~
-----oor
6
TUBE
~
CH
ECK
PO
SIT
IONS
L~o
'-
-
~-
__,
:~~-4
L_a_A_T_P_\_E_R_v__,
• POWER
PLUG
IS
CONNECTED
FOR
USE
WITH
EITHER
AC
OR
DC.
SERIES
PAD
Figure
4--Block
schematic diagram
PAD
OF'F'
LINE
MONITOR
LINE
0--0
LINE
+avu
FROM
1-----0
CUE
SOURCE
CUE
MONITOR
P-174434

STEAM POWERED RADIO.COM
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
6
INSTALLATION
Audio
Input Connections
Audio
input
conne~tions are made
through
four
standard
Cannon
female receptacles
marked
MIC-1,2,3
and 4
at
tlie
rear
of
the amplifier.
The
m:iting plugs
(RCA
Ml-4630
-B
or
Cannon
P3-CG-12S)
are
not
furnished
with
the amplifier.
The
MIC-I
and
MIC
-2
receptacles are each
connected
to
the
input
transformers
T-1
and
T-2
respectively.
The
MIC-3
and
MIC-4
receptacles .ire connected
through
switch
S-1
to
input
transformer
T-3.
Refer
to
figures 6
and
8.
To
change
the
wiring
on
the
input
transformers
as
described be-
low, first remove
the
bottom
and
back
cover
assembly
by loosening
the
eight
twist-lock
fasteners
which
hold
it
in place. Each fastener need
only
be
turned
¼
of
a revolution
with
a coin
or
screwdriver
.
Connections
to
Balanc&d
Source
Each
of
the amplifier
input
transformers
is
connected
for
operation
from
a
150-ohm
balanced source.
If
desired, a
250-ohm
balanced source
may
be
connected
to
this tap.
If
it
is
desired
to
use
one
or
more
30-ohm
sources,
change the wiring
to
~he
taps
on
the
primary
windings
of
the associated
input
transformers
as
follows:
a.
Remove the black lead
connected
to
terminal
num-
ber 1
and
connect
it
to
terminal
number
2.
b.
Remove the red lead
connected
to
terminal
num-
ber 4
and
connect
it
to
terminal
number
3.
On
all
balanced
inputs,
connect
the
audio leads
from
the source
to
terminals
number
2
and
3
on
the
input
plug used and
connect
the
shield lead
to
terminal
num-
ber
1.
Connections to Unbalanced Source
For connection to a
150-ohm
or
25
0-ohm
unbalanced
source, first remove
the
jumper
connecting
terminal
number
5
to
terminal
number
6
on
the
associated
input
transformers;
then
connect
terminal
number
5
to
terminal
number
1.
To
connect
a
30-ohm
unbalanced
source proceed
as
follows:
a.
Remove
the
jumper
connecting
terminal
number
5
to
terminal
number
6
on
the
associated
input
trans-
formers.
b.
Connect
terminal
number
5
to
terminal
number
2. c. Disconnect
the
black lead
from
terminal
number
1 and
connect
it
to
terminal
number
2.
d. Disconnect
the
red lead
from
terminal
number
4
and connect
it
to
terminal
number
3•
When
connecting
an unbalanced source
which
uses the
shield
as
one
of
the audio leads,
connect
the
shield lead
to
terminal
number
3
on
the
input
plug
and
connect
the
other
audio lead
to
terminal
number
2.
For
an
unbalanced
input
having
two
audio leads and
an electrostatic shield,
connect
the
low side
of
the
line
to
terminal
number
3
on
the
input
plug, the high
side
to
terminal
number
2,
and
the shield lead
to
terminal
number
I .
Output Conneetions
· Remove
the
panel
cover
by
pressing the
two
spring
buttons
on
the
sides
of
the
amplifier.
Output
connec-
tions are made
as
follows:
a.
Connect
the
telephone line
to
the
LINE
binding
posts.
b.
Connect
the
PA
binding
posts
to
the
input
of
the
public address amplifier.
c.
Connect
the leads
from
the cue source
to
the CUE
binding posts.
Ground
Connection
Connect
the
GND
binding
post
to
a suitable ground.
The
amplifier
may
be operated
without
an
external
ground
when
none
is
available, however best operation
is
obtained
when
the
amplifier
is
grounded.
Headphone
Jaeh
Headphones
may
be used
for
monitoring, however
none are supplied
with
the
amplifier'. Insert the plug
from
the
output
monitoring
headphones
into
one
of
the
telephone-type jacks
marked
LINE
MON
(J-6
or
J-7)
on
t_he
right-hand
side
of
the
amplifier. Insert the plug
,
from
the
cue-
monitoring
headphones
into
the jack
marked
CUE
MON
(J-5)
on
the
same side.
Meter
Pad
Connections
The
meter
pad
R-52
and
the
associated meter circuit
arc
conn«:tcd
so
that
the
meter
indicates O
vu
for a line
level
of
+s
dbm
or
+s
vu
when
the
meter switch
is
in the
+s
VU
position.
To
obtain
a
0-vu
indication
for
any
other
integral
line level in the range
of
+2
to
+
18
dbm,
it
is
necessary
to
reconnect
the terminals
on
the
meter
pacl
for
different
amounts
of
attenuation. A
convenient
method
of
determining
the
amount
of
at
-
tenuation
is
as
follows:
The
amount
of
attenuation
in
the
p.td
is
2
db
less
(numerically)
th.in
the
line level
corresponding
to
0-vu
indication
on
the meter.
For
example,
the
pad has its
2-db
apd
4-db
sections con-
nected
in
series
to
give a
6-db
attenuation,
and thus the
meter
reads O
vu
for
+ 8
dbm
or
+8
vu
line level.
The
pad
has sections
for
1, 2, 4, 8
and
12
db
of
attenuation
.
The
two
terminals
for
each
of
these sections are clearly
indicated by stencilled designations
on
the rear
of
the
pad between each pair.
If
necessary to reconnect the
pad, indicate in some
manner
near
the
met
.er-switch
panel-
marking
the new value
to
be used instead
of
the
+s
VU
designation.

STEAM POWERED RADIO.COM
•
•
•
•
."
•
•
•
•
-
!~
•
I
•
•
•
•
•
:
c.
•
•
•
•
•
•
1~
•
•
•
•
•
•
:~
•
•
•
•-
A-C
Power
Connections
The
amplifier
is
connected
for
a-c operation from a
115- to 125-volt, 50-
co
60-cycle power line.
For
operation
from
a
105-
to
11
S-volt line,
it
is
necessary
to disconnect the
black/red
lead
from
terminal
number
12
of
transformer
T-5
and
connect
this lead to terminal
number
11
ofT-5.
The a-c power cord
is
clamped to the inside
0£
the
front
panel cover
for
convenience in transporting. Re-
move this cord
from
beneath the clamps and insert the
12-terminal plug on one end
of
the cord
into
' the
receptacle on the rear
of
the amplifier. Insert the
two-
prong plug on the
other
end
of
the cord
into
a suitable
a-c outlet.
Tubes
Loosen the
four
twist-lock fasteners on the top cover
and remove this cover. Markings on the chassis indicate
the correct tube type for each socket. Place the tubes
in the sockets. Place the grid caps and grid-cap shields
on all
of
the amplifying tubes.
Each
shield
must
make a
good electrical connection to the shell
of
the tube
for
noise-free operation.
Battery
Connections
Six
RCA
Type VS012
"B"
Batteries
or
equivalent,
and 10
RCA
Type
VS004
"A"
Batteries
or
equivalent
may
be
used
to
supply
the
d-c power requirements listed
under Technical Data. A
kit
of
the above listed
bat-
teries may
be
ordered
as
Ml-112
55.
The
use
of
15
"A"
batteries will increase the
battery
life.
The
MI-11214
Battery Box may
be
used
with
the
Type
BN-2A
Ampli-
fier.
The
battery
box contains space for
15
"A"
batteries and 6
"B"
batteries
of
the types listed above.
The Ml-11214
Battery
Box
is
wired
with
plugs ready
to
be
inserted
into
the batteries and
is
supplied
with
a
power cord
for
direct connection to the receptacle
on
the amplifier.
The
battery
connector
plug
is
wired
as
'shown in the lower-left corner
of
the schematic diagram,
figure
8.
The
expected
battery
life
for
an average amplifier
operation
of
six hours per day
is
as
per the table below.
If
the amplifier
is
used
less
than
six
hours per day, the
expected life
of
the
battery
in hours will
be
increased.
If the amplifier
is
to be used continuously the life
of
the
battery will
be
materially decreased.
EXPECTED
LIFE
IN
HO
URS
(
APPROXIMATE)
Q11anlity
HA"
or "B"
Typ,
Li/, in Hours
15
10
6
A
VS004
8.J
A
VS004
4
B
VS0l2
12f
NOTE:
For
maximum
battery
life remove alt
battery
plugs when che
battery
supply
is
not
to
be
used .for
24 hours
or
more.
7
OPERATION
Set the
LIGHT
switch for the desired meter illumina-
tion
(LO
or
HI).
(The
meter lamps also serve
as
power-on-off indicators.) Set this switch in
"LO"
position when using batteries
to
reduce drain on the
batteries.
Turn
the
POWER
swi\cb
ON
and allow
ah'out
30
seconds for
tube
warm-up. Before broad-
casting
has begun,
turn
all volume controls to maximum
and check carefully for extraneous
noises
in the
output
which may be due
to
faulty
location of the microphones
and cables.
When
using the MIC-3 or MIC-4 input, set
the MIC
switch
to
the corresponding number. Rotate
the
METER
switch
to
the
"+s
VU"
position.
Output
level to .the telephone line should
be
+s
vu. Adjust
the gain controls
so
that
the peaks
of
modulation swing
the needle
of
the
meter
to
zer~ on the upper scale (for
an average line level
of
+8
vu).
This zero reading will
represent a different line level if the connections to the
meter pad have been changed
as
indicated under In-
stallation.
For
the best signal-to-noise ratio the MAS-
TER
gain control should be set
at
a fixed.position some-
where between
number
IO
and number
16
and the mixer
controls
(MIC
1,
2, 3 &
4)
should
be
adjusted for the
zero reading on the meter. This arrangement permits
varying the mixers
from
number
Oto
number 16 without
adding more
than
2
db
to the noise level
of
the amplifier.
The
MASTER
and MIC controls also control the level
at
the
output-monitoring
jacks.
Switching
to
Telephone
Line
To
switch
the
output
of
the amplifier into the tele-
phone line,
turn
the
AMP
OUTPUT
control to LINE.
To
switch the
output
of
the
amplifier
off
the telephone
line,
turn
the
AMP
OUTPUT
control to
OFF
.
Switching
to
PA
Amplifier
To
switch
the
output
of
the amplifier into the input
of
a connected public address amplifier,
turn
the PA
INPUT
switch
to
AMP.
To
switch the input at the
CUE
terminals
to
the
input
of
the public address am-
plifier, set the
PA
INPUT
switch to CUE. Adjust the
PA
VOLUME
control
for
the desired
output
from the
public address system.
To
switch both amplifier and
cue
inputs
off
the
public address amplifier,
turn
the
PA
INPUT
switch to OFF.
SERVICE
Tube
Checking
with
VU
Meter
To
check
the
tubes, rotate the METER control
through
posidons 1 through 6 and observe the
VU
meter
at
each step. These
meter
positions check V-1 through
..

STEAM POWERED RADIO.COM
'
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
t.
•
•
•
•
•
•
•
•
•
•
•
I
•
•
•
•
•
I
I
••
•
•
•
•
•
•
8
RCA
1620
1 fIr
CHASSIS
CiR
OU
NO
R
CA
1
62
0
RCA
1620
~ ~
I1It1
RCA
1620
IiII1 g
! 0 2
~
l
11
..
.,
~
!'!
l l1
ALL
VO
LTAGES OC
UNL
ESS
OTHERWISE
N
OTEO
12.0- V0 LU
OH
120-V0LT
UP
lr'C
V0LTAGC$ M
fA$UR(
0
WllH
20.000
0HM$
/YO
L.
T
METER
.
Figure
5-Tube
socket voltages
V-6
respectively (fig.
8).
The
meter readings are e
ac
h
an indication
of
th
e emission
of
the tubes., The normal
meter reading for each
tube
should
be
O
±2
(on
VU
sc
ale).
Note
that
two spare tube sockets are provided
on the bottom side
of
the top cover
for
carrying spare
tubes.
Cleaning Volume Controls
Remove the
bottom
and
re
,
ar
covci: ass~mbly
of
the
amplifier. Press the spring fasteners
on
the rear covers
of the volume controls and remove the covers.
Apply
Davcnoil, which
is
furnished
with
the amplifier, to
the
contact
s, and rotate the knobs.
If
any dark streaks
appear, wipe off the contacts. Repeat this procedure
until the contacts are clean, and
then
apply a
thin
film
of
Davenoil for lubrication.
The
Davenoil
is
provided
for cleaning and lubri
cating
the volume controls and
no other cleaning agent·should
be
used.
Operating
Voltages
Refer to figure 5
for
the tube operating voltages.
The voltages listed are approximate,-
but
readings should
not vary more than about 20 % of the values given. If
the
voltmeter
used has a met
er
resistance of
less
than
20,000 ohms-per-volt, most readings taken will vary
accordingly, the
amount
of
variation depending upon
the
circuit
across which the meter
is
connected.
Fuse
Replacement
When
replacing a fuse, make sure
that
the replace-
ment
fuse
is
of
the same type and rating (1 ampere)
as
the one furnished
with
the amplifier.
To
use
a fuse
of
higher
rating
for replac~
ment
purposes will needlessly
end,rnger the windings
of
the power transformer.
Note
that
a spare fuse
mounting
is
provided on the bottom
side
of
the top cover for carrying a spare fuse.
Replacement
Parts
The following parts list
is
included to provide identi-
fication when ordering r~placement parts. Order from
RCA
Replacement Parts Department, Camden, New
Jer
sey, giving the Stock Number and
De
sc
ription of the
parts wanted. Replacement parts supplied may
be
slightly diffe.
rent
in
form or size from the original parts
but
will
be
completely interchangeable
with
them.
LIST
OF
PARTS
Symbol Stoc
k.
Symbol Slock.
No. Dc,criptio,z
No
.
No
. Drscription No.
C-1
Capacitpr, elec, 3 sections: "
A"
C-2,3 Capacitor, oil filled,
0.25
mf
40
mf -
25
v,
"B"
&
"C"
15
±1
0%,
400
V
55811
mf -450 V 34150 c~ Same as
C-1
•

STEAM POWERED RADIO.COM
'
:
•
Jlt
t
•
-
'
•
~
:
\I
•
•
~
•
•
I
•
M
•
-
•
•
'
•
.l\t
•
•
•
=
•
•
•
lt
•
•
•
S
ymbo
l
No.
C-5
C-6,7
C-8
C-9
C-10
C-11
C-
12
C-
13
C-14
C-
15
C-16,17
C-18
C-
19,20
C-21,22
F-1
J-1,2,3,4
}-5,6,7
M-1
P-1
R-1
R-Z
R-3
R-4
R-5
R-6
R-7
R-8
R-9
R-10
R-
11
R-12
R-13
R-14
R-15
R-16
R-17
R-18
LIST O F PA RT S (Continued)
De,crif,tion
Same
as
C-2
Same
as
c : 1
Capacitor,
oil filled,
0.5
mf
±20%, 400 V
Capacitor,
paper,
oil
impreg-
Stock
No,
55812
nated,
0.05
mf
± 10%, 600 v 55g13
€1.pacitot,
mica,
!lOO
1m1rf
C-/1:,
iil.>10%,
!iO!h•S11.M~ ·
IIS
-4&rn
Capacitor,
oil filled, 0.05
mf
± 10%, 400 V 55814
Same
as
C-2
Same
as
C-9
Same
as
C-Z
Capacitor,
paper,
oil
impreg
-
nated,
O.~
mf
± 10%, 400 v
Capacitor,
molded
,
paper,
0.0015 mf, 600 V
Capacitor,
metalized
paper,
0.
25
mf,
200 V
Capacitor,
elec, 40
mf,
450 v
Same
as
C-16
Fuse
, 1
amp
Connector,
female, 3
contacts,
chassis
mounting
J
ac
k,
open
circuit
phone
jack
Meter,
VU
volume
level
indi-
cator,
illuminated,
scale
"A"
calibrated
for
.047"
steel
panel
,
panel
angle
10
de-
grees,
black
Connector,
male,
12
contacts
Res
is
tor,
comp
, 1800
ohms
±
5%,
1 w
Resistor
,
comp,
680
ohms
::±:
5%,
1 w
Resistot
,
comp,
100,000
ohms
±IO%, 1 w
Resistor
,
comp,
27,000
ohms
±10%, 1 w
Resistor
,
attenuator,
carbon,
20
steps
of
2
db
each
to
infinity, 100,000
ohms
Resistor
,
comp
, 220,000
ohms
±10%, 1 w
Same
as
R-1
Same
as
R-2
Same
as
R-.3
Same
as
R-4
Same
as
R-5
Same
as
R-6
Same
as
R-1
Same
as
R-2
Same
as
R-3
Same
as
R-4
Same
a$
R-5
Same
as
R-6
..
55815
55816
55817
37308
14133
25598
43921
55818
19679
55819
Symbol
No.
R-19
R-20
R-21
R-22
R-23
R-24
R-
2S
R-26
R-27
R-28
R-29
R-
30
R-31
R-32
R-33
R-34,3S
R-36
R-
37
R-38,
39
R-40
R-41,42
R-43,44
R-4S
R-46,47
R-48
R-49
R-50
R-
51
R-52
D
c,c
ri
ption
Resistor,
comp,
1.2
meg
±10%,
1 w
Resistor,
comp,
1100
ohms
±
5%,
l w
Resistor,
comp,
S6
,000
ohms
±10%, 1 w
Same
as
R-19
Same
as R-6
Resistor,
comp
, 3300
ohms
±
5%,
l w
Resistor,
comp,
2700
ohms
~-
s%,
1 w
Resistor,
comp,
2,7
meg
±10%, l w
Resistor
,
comp,
470,000
ohms
±10%, 1 w
Resistor,
comp,
S60,000
ohms
±
S%,
l w
Resistor,
comp,
12,000
ohms
±10%, 1 w
Resistor,
comp,
1
meg
±10%, 1 w
Resistor,
comp,
130
ohms
±
5%,
1 w
Resistor,
comp,
360
ohms
±5%, 1 w
Resistor,
comp
, 120,000
ohms
±
5%,
1 w
Resistor,
comp,
4700
ohms
±10%, 1 w
•
Resistor,
variable,
dual,
300
ohms
per
section
±20%,
shaft
,249"
diam
x ¾" in-
cluding
¼"
bushing
fiat
nr"
body
1rtr"
diam
x 1
fa
"
Resistor,
attenuator,
ladder
pad
Same
as
R-34
Resistor,
comp,
560
ohms
±
10%,
l w
Resistor,
comp
, 2200
ohms
±10%,
l w
Resistor,
comp,
39
ohms
· ± 10%, 1 w
Same
as R-25
Same
as
R-43
Same
as
R-40
Resistor,
comp,
3900
ohms
±10%, 1 w
Same
as R-27
Resistor,
cod;p,
22,000
ohms
±1
0%,
1 w
Resistor,
attenuator,
multiple
pad,
impedance
7100
/
3900
ohms,
maximum
attenua-
tion
27
db
1
9
Stock
No.
54667
43115
I
19328

STEAM POWERED RADIO.COM
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
IO
v-
c
~2
R-1
V-3
S-5
S·t
V- 1
V-2
c-1
Figure
6-Location
of
parts, rear 'view
R-
37
R-42
C-16
:.:;.y-
41
....-.::=-=::~p.=-,=:-:-::,
,-
-=:p=--.::::::~=1=-:-:J::=:::;l=::=r-:-\-\-\-~~~~"'"~J
R- 8 R- 7 R
-1
4
R-13
R-21
R
-23
R-49
R-50
R
-20
C-
18 R-
51
R-25
C-17 R
-2
4 C-15
auu
Figure
7-Location
of
/?arts,
bottom
view
with
attenuator caps
removed
•

STEAM POWERED RADIO.COM
•
•
•
•
•
•
•
•
•
•
•
•
•
•
I
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1
'"
!
55·3/>.
MIC
-3
MIC
4-
eArrERY
CONNECTOR
.,.
FROl./r
VIEWS
'O
u
A . C.
CONNG'CTOR
.Q
.C
LINE
RJ7
I_
our
C/7
/500MMF
Pl
TS

STEAM POWERED RADIO.COM
•
t
•
•
•
•
•
•
•
•
C:
... 0
No
Ci"'
"'
C
II
.
OSMF'O
Cl:!:>
.O!SMf"O
CIG
.
5MFD
V•',
r-
------
' a
I
I
I
I
I
I
t; I
4700-ll.
0
0
S·3
cu
C I 4 I
•
--
--i
-+--
+--;cior:-h,+,;.-~~~~~----+ti:__+-_j
__
'-
...l
- - - - - - - -
_J
•
•
•
•
•
•
•
•
•
•
•
•
t§
ro
1ol.O (
"J
1
;.;EIJTt.11'.S
7 2
,-,a
R5+ 22.I\.
S·6
S-5
... i
~
.:le •
OFF'
1.
• +av.lJ.
A
Ill.
_
{_
J
B
•
e
OFf
~41
azoo..n..
VO\.:.UMC
INOICA,-OFI.
=
T-1042O1
- 1
,.)ti,
v 7
Figure 8--Schematic
diag

STEAM POWERED RADIO.COM
12
Symbol
No.
R-53
R-54
R-
55
S-1
S-2
S-3
S-4
S-5
S-6
LIST O F PA RTS
(Continued)
Dtt
criJ,llon
Resistor,
comp,
430
ohms
±5¾,
1 w
Resisto
'
r,
comp,
22
ohms
±10¾,
l w
Resistor,
comp,
5600
ohms
±5¾,
1 w
Switch,
rotary,
DPDT,
locking
Switch,
toggle,
DPST,
rated
2
amp,
250
V
Switch,
rotary,
2
section,
3
position
Same
as
S-1
Switch,
rotary,
2 section,
8 position
Same
as
S-2
Stoc:lc.
No.
55820
43281
55821
55822
Symbol
No.
T-1,2,3
T-4
T-S
X-1,2,3,4
X-5,6,7
X-8
D
tsc:
rlj,lion
Transformer,
input,
ratio
full
pri
to
sec
1:18.2,
pri
taps
to
sec
1:40.8
Pack,
comprising
output
trans
-
former
ratio
pri
to
sec
7-9
17.85:1,
and
reactor
200
h
Transformer,
power, pri
60
eye 120/110 v, plate 230-0-
230 v .014
amp,
filament
6.3
v,
center
tap,
2.7
amp
Socket
,
tube,
8
contacts
Socket,
tube, 8
contacts
Holder,
fuse
Catch
,
front
cover
Knob,
for S-1,3,4,5
and
R-36
Knob,
for
R-5,
11,17
and
37
Mountin
, fuse
mounting
clip
Sta
c
ie.
No.
55823
55824
55834
28413
31319
48894
28687
30075
17269
13526
-

STEAM POWERED RADIO.COM
Table of contents