PAGE
16
««««««
l
~iEICQL
1
667
TUBE
TESTER
to position
6;
3)
Connect
all
unused pins and
internal shields
to position
1
(ground)
unless otherwise
specified
by
the manufacturer;
4)
All
detecting diode
plates
(such
as
in the 6SQ7) must
be
connected
to position
6;
5)
For tubes having a
maximum
allowable
DC
plate voltage
less than
70
volts, position
3
must
be
used
for the
plate.
d)
Insert the tube in
the socket
and
allow
it to heat up.
Make
the
line
adjustments in
the usual manner. Then determine
the push-buttons
to
be
pressed
in
the leakage
tests
by
consulting
the
base
diagram
of the
tube
and
selecting
the pin numbers
which
correspond to the elements.
If
the tube
has an
indirectly
heated
cathode, note
which
pin
number
is
the cathode
(for
heater -cathode leakage testing;.
The pin
numbers
so determined
correspond
to
the
numbers
of
the
push-button
switches to
press
for
the
leakage
tests.
Enter
the
numbers of
these
push-buttons in
the LEAK column
of
the
roll chart,
underlining the
cathode
button. It
may
be
convenient
to
refer
to a
similar tube
type
in
making these
settings.
e)
If
the leakage
tests
described above show
the
tube
satisfactory, proceed with the
MERIT test
procedure.
If
the
leakage test
results are unsatisfactory,
do not
proceed
with further testing on
the faulty tube, or
the tube
tester
may
be
damaged.
f)
Refer
to the base
diagram
for
the tube
and determine the pin number for the
plate.
This
push-button
number
should then
be
listed in the MERIT column
and
should
correspond to the
lever
which
you had set to
position
4
(step
c
above).
Press
this
button, remembering that
this
constitutes a
plate-to-all
leakage
test
until
the
MERIT
lever is
pulled
down.
g)
Refer
to
the published
characteristics
of the tube to
find the maximum
allowable
plate current, or the
highest
typical operating
current
listed.
Locate
this
plate
current
in
one of the
charts
1-5.
Read
the
corresponding settings of the
PLATE
control
and
the
chart number. Set
lever S to the chart
number,
and the PLATE
control
to
the value
as
read
from
the
chart. Doing so
establishes that
the meter
will read
100 on the scale
when the
plate current of the tube is
equal to the desired
value.
h) Consult the
published tube
characteristics
again
and find
the
maximum
allowable
dc
plate voltage. Note
that
lever
Vapplies
45
volts
atpositionl,
90 volts atposition
2,
and 180
volts
at
positions
3
and
4
(all
in
volts rms, 60cps).
The
highest
position
of
the
V lever that may be
used is
the one at which
the rms plate
voltage
applied
does not
exceed roughly
two-thirds
of the
maximum
rated dc plate voltage.
i)
Set lever
V
at
position 1
and the GRID
control at
7.
Hold
down
the
MERIT
lever
and
note
the meter
indication.
Increase the GRID
control until a meter
indication
of 100 is obtained. If
this
is
not
possible,
release the MERIT
lever, return the
GRID
control'
to
7,
and
advance the
V
lever
to
position
2.
Again
hold down
the
MERIT
lever and
adjust
the GRID
control
for
a
meter indication of 100.
Continue
this
procedure,
setting lever V to
positions
3 or
4,
if
necessary,
to
obtain
the
100
meter indication.
If
the
GRID
control appears to
"saturate", that is, if
an increase
in its setting
causes
very little increase in the
meter
indication, lever V
should be
advanced to the next
position.
Be
careful
not to
exceed the maximum
allowable
plate voltage
when making this setting.
For
the
new 12 volt automobile radio types
(30
volts
dc maximum
plate
voltage), set
the
plate
element
lever to
position
lonly.
When the
correct
V
lever and
GRID
control settings
are
found,
release
the MERIT
lever
and
remove the tube from
the tester.
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