Heathkit TC-2 - Instrument Description

INSTRUMENT DESCRIPTION
The
Heathkit
model
TC-2
Tube
Checker
was
expressly
designed
for
checking
tubes
encountered
in
everyday
radio
and
TV
service
work.
It
is
capable
of
providing
an
overall
quality
test,
will
indicate
shorted
elements,
open
elements
and
filament
continuity,
It
will
check
4,
5, 6,
and
7
pin,
large,
regular
and
miniature,
octal,
loctal,
Hytron,
9
pin
miniature
series
tubes
and
pilot
lamps.
Separate
tests
ior
the
oscillator
section
of
converter
tubes
have
been
provided.
A
blank
socket
is
arranged
on
the
panel
to
facilitate
modification
for
checking
newly
added
tube
types
as
protection
against
obsolescence.
The
roll
chart
contains
all
necessary
data
for
the
checking
of
currently
used
tubes.
Because
of
the
constantly
growing
list
of
tubes,
it
was
decided
to
eliminate
tubes
classified
as
seldom-
used,
or
obsolete,
in
an
effort
to
hold
down
the
physical
length
of
the
roll
chart.
The
informa-
tion
for
various
settings
of
the
tubes
in
this
particulat
classification
is
supplied
on
a
separate
sheet,
The
Heath
Company
periodically
revises
the
rol]
chart
in
order
to
provide
the
latest
test
information.
Announcement
of
new
chart
availability
is
usually
made
in
Heathkit
Flyer
adver-
tising
and
replacement
charts
can
be
obtained
for
a
nominal
charge
of
fifty
cents
($0.50).
One
secondary
winding
of
the
power
transformer
is
tapped
for
fourteen
different
filament
volt-
ages
which
range
from
.76
volts
upto
110
volts.
Such
an
arrangement
assures
placing
the
prop-
er
filament
voltages
on
the
hundreds
of
tubes
listed
on
the
chart
and
the
filament
switch
makes
Proper
connections,
The
other
secondary
winding
has
voltage
taps
of
30
voits,
100
volts
and 250
volts,
and
the
vari-
ous
tests
use
these
different
voltages.
Three
basic
circuits
are
set
up
as
the
tube
is
checked
and
these
operate
in the
following
manner.
The
first
basic
circuit
is
used
when
making
the
quality
and
open
checks.
In
these
tests,
30
volts
AC
are
placed
across
the
tube
between
filament
and
plate
and
the
tube
under
test
conducts
as
a
half-wave
rectifier.
The
filament
and
cathode
are
connected
together
as
are
the
plate
and
the
grids.
The
PLATE
adjust
control
adjusts
the
sensitivity
of
the
BAD-GOOD
meter,
which
is
in
the
circuit
at
this
time.
Theroll
chart
gives
the
setting
for
PLATE
adjustcontrol
and
a
good
tube
with
the
sensitivity
of
the
meter
properly
set
will
have
sufficient
cathode
emission
to
swing
the
meter
needle
to
the
GOOD
position.
if
the
tube
emission
is
toc
low,
the
conducting
current
of
the
tube
will
not
be
high
enough
to
bring
the
needle
into
the
GOOD
section,
rather
into
the
?
or
BAD
section.
Thus
the
cathode
emission
is
checked.
Basically,
the
open
check
works
as
follows.
The
plate
and
all
grids
connected
together
will
receive
a
certain
amount
of
electrons
from
the
cathode.
The
meter
reading
with
this
flow
is
noted.
Then,
to
test
each
element
individually
for
opens,
each
of
the
grids
is
in
turn
discon-
nected
and
if
the
element
is
not
open,
the
current
through
the
meter
drops
and
the
reading
is
less
than
originally
noted.
If
an
element
is
open,
it
is
recognized
because
the
meter
reading
does
not
drop
when
this
element
is
checked.
For
tubes
with
quite
a
number
of
grids,
the
opera-
tion
is
somewhat
more
complex,
but
the
same
theory
applies
in
general.
For
gas
tubes,
(OZ4,
ete.)
the
250
volt
tap
rather
than
the
30
volt
tap
is
used.
The
circuitry
remains
unchanged,
The
second
basic
circuit
is
used
in
short
and
filament
continuity
test.
‘The
100
volt
tap
is
con-
nected
to
the
neon
bulb
short
indicator
and
associated
network,
and
is
in
series
with
the
plate
Of
the
tube
being
tested.
The
meter
is
not
now
in
the
circuit
and
the
checks
are
indicated
by
the
neon
bulb.
Putting
the
switches
in
the
positions
as
indicated
on
the
roll
chart,
connect
the
var-
ious
tube
elements
in
such
a
manner
that
a
shorted
element
will
cause
considerable
increased
current
flow
through
the
resistor
in
parallel
with
the
neon
bulb.
The
voltage
drop
then
produced
reaches
the
operating
voltage
of
the
neon
bulb,
and
it
glows
brightly
indicating
a
short.
For
the
filament
tap
continuity
test,
the
filament
setting
is
reduced
to
.75
volts
and
with
continuity
the
neon bulb will glow.
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