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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 M -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. f 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. f 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.
n 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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