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cable.
Placing the
splice
in
an alcohol or bunsen
flame
affords
sufficient
heat and
allows
any
excess
solder to
drip
away.
It
is
to
be
understood
that
this
is
but
a
temporary
repair and
should
be used only
until
a
new
cable can
be
procured and installed.
(13)
USING RADIOLA
16
WITH
RCA "B" BATTERY
ELYMINA-
TOR OR SIMILAR DEVICES NOT SUPPLYING
67
VOLTS
PLATE VOLTAGE
Radiola
16 uses
a.plate
voltage
of 67 volts
for the radio frequency amplifiers and it
is
important
that
this voltage
is
not
exceeded.
(See
Figure 5).
A
higher voltage may
cause
it
to oscillate and
in
all cases seriously affect its tone
quality.
It
is
imperative
that,
when
using
"B"
battery
eliminators having
fixed
90
-volt
taps,
provision
be
made
for
GRID
LEAK
BY
PASS:'
CONDENSER
OUTPUT
o
13+135
.....
RED
A+
A-
-4_,,
O+B-
}...
SWITCH='
GND
FILAMENT
RESISTOR;
W
BY
-PASS;'
CONDENSER
DETECTOR
TAPPED
RESISTOR
YELLOW
BLACK
WITH
YELLOW TRACER
GREEN WITH
RED AND
BLUE
TRACER
O
8+67MAROON
&
LED
o
B+45MAROON
l
c
9
BLACK WITH
GREEN TRACER,
and wiring color
scheme
for
making
battery
connections
reducing them to 67 volts.
Off
hand it
would
seem
that
a series resistance could
be
used
to
drop the voltage, but
when
we
realize the
plate
voltage varies
in
practically
all of these
devices
except
in
the case of the RCA
"B"
Eliminator (Duo-Rectron)
and similar
devices
a fixed
resistor
would give a
varying voltage depending
on
the device.
A
potentiometer having
sufficiently high
resistance
(at
least 18,000
ohms) shunt-
ed
across the
+45V
and
+90V taps
with
the contact arm connected to the
67
-volt lead
from the receiver
will
give a
variable voltage
between 45
and
90 volts
for this lead. By
taking
a
high resistance voltmeter and connecting from
-B
to this arm,
it
may
be
ad-
justed for
67 volts.
A
drop
of solder will make a
permanent connection
between
the arm
and resistance
element
and prevent
a
possible change
in
voltage.
The General Radio
Potentiometer No. 371 (18,000 ohms)
is
recommended
for this purpose.
11
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