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RCA BA-13A - Maintenance

RCA BA-13A
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6
CAPACITOR
VALUES
k
\
I
MAINTENANCE
CAPACITOR
VALUES
Response
Curve
Number
1
2
3
5,600
8,200
10,000
Response
Curve
Number
1
2
3
0.03
0.05
0.1
C-5
{200
vdc)
Capacity
in
mmjd
C-4
(400
vdc)
Capacity
in
mjd
amplifier
can
be
replaced
with
the
dual
step-type
attenuator
furnished
in
the
MI-11233
amplifier.
Order
from
RCA
Replacement
Parts
Department,
Camden,
New
Jersey,
specifying
stock
number
57121.
This
attenuator
is
similar
electrically
to
the
continuous
type
of
attenuator
and
must
be
wired
into
the
circuit
as
shown
on
the
wiring
diagram,
figure
8.
capacitor
having
the
curve
number
in
the
Increasing
High-Frequency
Response
Three
curves,
numbered
1,
2
and
3,
are
shown
in
figure
6.
These
curves
illustrate
the
frequency
characteristics
of
the
amplifier
after
changes
are
made,
in
the
circuit
constants,
to
increase
the
high-
frequency
response
of
the
amplifier,
by
approxi
mately
one,
two
and
three
decibels
at
10,000
cps.
To
obtain
a
frequency
response
corresponding
to
one
of
the
three
curves,
replace
the
3900
mmfd
capacitor
designated
C-5
in
figures
2
and
4
with
a
capacitor
having
the
value
given,
opposite
the
curve
number,
in
the
following
table.
ts
and
NOTE:
Check
the
high-frequency
response.
If
it
is
found
to
be
too
high,
substitute
for
C-5
a
capacitor
of
the
next
lower
standard
value
as
required.
Increasing
Low-Frequency
Response
The
curves
numbered
1,
2
and
3
in
figure
7
show
the
frequency
response
of
the
amplifier,
after
alterations
have
been
made
in
the
circuit
to
obtain
greater
low-frequency
response.
An
increase
of
2,
3
and
4
decibels
at
30
cps
can
be
obtained
by
making
suitable
modifications
in
the
circuit.
To
Frequency
Compensation
The
normal
frequency
response
of
the
Type
BA-13A
Program
Amplifier,
shown
by
the
curve
in
figure
5,
is
flat
throughout
the
audio
range.
Under
certain
conditions
it
may
be
desirable
to
increase
the
response
at
either
the
high-frequency
or
the
low-frequency
end
of
the
range.
The
curves
in
figures
6
and
7
show
the
increase
in
response
which
may
be
obtained
by
making
compensation
adjustments
within
the
amplifier,
according
to
the
instructions
in
the
following
paragraphs.
If
desired,
both
high
and
low
frequency
compensation
may
be
applied.
NOTE:
Because
of
slight
differences
in
wiring
and
tolerances
of
component
parts,
it
may
be
necessary
to
use
capacitors
differing
in
Value
from
those
given
in
the
following
tables
in
order
to
secure
the
desired
response.
Cleaning
The
care
of
the
Type
BA-13A
Program
Amplifier
should
include
the
usual
precautions
observed
in
the
maintenance
of
high-quality
audio
components.
Do
not
allow
dust
or
dirt
to
accumulate
on
the
amplifier.
Perform
the
following
operations
at
regular
intervals:
a.
Clean
the
tube
prongs
and
the
contacts
in
the
tube
sockets.
b.
Clean
the
prongs
of
the
plug-in
capacito
the
contacts
of
the
capacitor
sockets.
c.
Keep
the
prongs
of
the
amplifier
connection
plugs
clean
using
clean
dry
cloth.
Do
not
use
abrasive.
Clean
the
connection-plug
recep
tacles
approximately
every
two
months
by
obtain
a
frequency
response
corresponding
to
one
of
the
three
curves
make
the
following
changes:
a.
Disconnect
the
yellow
lead
from
R-15
(on
terminal
No.
1
of
terminal
board
1)
and
connect
this
lead
to
a
compensator
composed
of
a
5600-ohm
resistor
and
a
1-mfd
capacitor
(in
parallel).
Connect
the
other
side
of
the
compensator
to
R-15
on
terminal
No.
1
on
terminal
board
1.
The
com
pensator
may
be
supported
by
a
small
terminal
board
mounted
on
the
side
wall
of
the
chassis.
The
position
in
the
circuit
of
the
resistor
and
capacitor,
identified
as
R-27A
and
C-15A
is
shown
in
figure
4
(they
should
have
ratings
of
1
watt
and
200
vdc
respectively).
b.
Replace
the
0.25
mfd
capacitor,
designated
C-4
in
figures
2
and
4,
with
a
value
given
opposite
the
following
table.
In
applications
where
system
losses
or
other
deficiencies
require
an
increase
in
the
response
at
both
ends
of
the
audio
spectrum,
some
suitable
combination
of
high-frequency
and
low
’
-frequency
compensation
can
be
selected
and
applied
as
described
in
the
two
preceding
paragraphs.

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