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The
values of the
various resistances are
shown
in
the schematic
diagram Figure
5.
In
some cases with
certain antennas, the Radiola may oscillate
even
though
every-
thing
is
O.
K.
The remedy
in
this case
is
to
interchange
the
Radiotrons or to
reduce the
volume
control
a
slight amount.
(16)
AUDIO HOWL
An
audio
howl
is
generally caused
by some defect in the audio
amplifying
system.
One of
the following defects may
be
the cause of this
howl.
1.
Defective
Radiotron.
2.
Defective
"B" battery.
3.
Open
audio by-pass condensers.
4.
Defective
grid
leak or open
grid
of
any tube
in
the
Radiola.
5.
Open
R. F. grid resistor.
6.
Open
by-pass condenser across secondary
of first audio
transformer.
ACROSS
RESISTANCE
.
R
-
E
OR
1000
VOLTS
TO SE
MEASURED
I
MILLIAMPERES
0-7
6 VOLTS
200
OHMSte
Figure
6-Schematic
circuit for resistance
measurement
(17)
DISTORTED REPRODUCTION
Under normal conditions Radiola
16 will
deliver
a
strong
signal
of good
quality to
the loudspeaker.
If
the loudspeaker production
is
poor, test the loudspeaker input
from
the receiver.
A
pair
of phones or
a
loudspeaker
of known
quality
may
be used
for this
purpose.
If
the
output
of
the Radiola
is
of
poor quality
the
distortion
may
be
due to
any
of the following causes:
1.
Excessive voltage
on
R.
F.
amplifiers.
2.
Excessive filament voltage.
3.
Defective
Radiotrons. The Radiola
may
be
operating properly, but
a
poor tube
in
the detector or audio stages
will
cause
distortion.
4.
An open audio
transformer
may cause
distortion.
(18)
ACOUSTIC HOWL
This
is
caused by
a
microphonic
Radiotron,
or the Loudspeaker being too
close
to
the Radiola. The sound
waves
from the loudspeaker
striking
a
Radiotron
may cause the
Radiotron
elements to
vibrate,
which in
turn,
produces an
amplified howl
in
the
output
of
the loudspeaker.
The
remedy lies in
interchanging
the
Radiotrons. Counting
from
left to right
the
third Radiotron
is
the most susceptible to this microphonic condition.
Interchanging it,
with one of the
R. F. amplifiers or placing the Loudspeaker
at
a
greater
distance from
the receiver
will
generally
remedy this condition,
In
some cases
both may
be
necessary.
18
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