OSCILLATOR
STRENGTH: The negative
d~c
voltage
developed
Of
the oscilla-
tor
grid
is always directly proportional to the strength
of
oscillation.
This
voltage
can
be measured very
readily at
the
osci
Motor
grid
while the
band
switch
is turned
to the
various
bands, and
in
each
of
its
positions the main
tuning
condenser is rotated from minimum
capacity.
This
will
give
an indica-
tion of
the strength of
oscillation
at
all frequencies
within
the oscillator's
range.
A-V-C VOLTAGE:
The automatic
volume control voltage developed
by
the
incoming
signal can be measured
at
a number
of
places
in
the
receiver. This
negative
voltage
first
appears
across the
diode
load
resistor.
It may also
be
measured along the a-v-c bus and
at
the
grids
of the r-f
tubes being
controlled.
The
d~c voltage measured at the diode
load
resistor
is
a very
convenient out-
put indication
during
receiver
alignment.
Owing
to
the
high input resistance
of
this
instrument,
It is
possible
to
measure
bias
(a-v-c)
voltage on
the
grid of
r-f
and
?-f
amplifier
tubes
without
disrupting
the
signal.
D~C
SUPPLY
VOLTAGES:
Power supply d~c
voltages
can
be measured
at
the
rectifier
filaments
and
in the filter circuits.
Plate,
screen,
and cathode d-c
voltages can
be measured
at
the
corresponding pins of
the
tube
sockets.
BIAS
CELL VOLTAGE-
This
instrument
will
accurately
measure
the voltage
of
a bias cell.
Current
drawing
voltmeters
are
not
capable
of
making
this
meas
-
urement
and
in many
cases will damage the cell.
TELEVISION RECEIVER ADJUSTMENTS: This instrument
will
measure
the d-c
voltage
developed across the second-detector
load
resistor
In the
picture channel
of
a television receiver. This measurement
h
most
useful
when
adjusting an-
tenna orientation
as
we'
'
as
when adjusting
antenna
matching sec Lions.
GASSY
TUBES: One effect
of
a gassy tube
is to
reduce
rhe
normal new.
grid
bias, or
even make the grid positive.
This instrument
is
idea!
for
meas-
uring
the voltage directly
at the control
grid
of
any
tube
in order to d
tvr.Lpe
whether
or
not
this
effect
is present. Excessive gas
will cause
the tube L,
rise
operating
normal
iy
,
and
in an
audio
amplifier wi I
!
usual
ly
cause the volume con
frol
to
become
noisy.
This amount
or
gas
will
not always produce
a
noticeable
change in
the operation of the radio receiver. Consequently
if
repeated
diffi-
culty
is experienced with
volume
controls becoming
noisy, in
this type
of
cir-
cuit, this
instrument
should
be
used to check
for incorrect bias.
A-C
VOLTAGES:
The o-c
voltmeter wirhin the
instrument
is extremely useful
in
measuring ali a~c
voltages encountered
in
the
average radio
receiver.
The
measurements that
can
be
made
include
ali
voltages from power transformer
secondaries, audio signal
voltages
at
grids and
plates
of amplifiers,
and
audio-
voltages
developed
across the
output
transformer
or
voice
coil
(as an
indication
of
output during
receiver alignment).
"
6
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