Heathkit TT-1 - Page 11

10.
iy iy
12,
detrimental to the operation of the tube.
In some cases, however, a “borderline”
condition may exist. That is, the tube is
suspected to be drawing grid current in its
normal application but there is no evidence
of grid current shown by the tester. Grid
current may be the result of an increase in
bulb temperature due to prolonged operation
or other nearby heat-producing components.
A more thorouch check on the "borderline"
fo SAUD ese ges Veet Ua Uae Lt WR MOS BSE
tube may be made by allowing the tube to re-
tube is located "out inthe open" ' (when in the
tester), the movement of air around the bulb
keeps the temperature down. Placing an
unventilated tube shield around the tube will
block off the air flow and raise the bulb
temperature. As an extreme measure, the
heater voltage may be increased, the amount
of increase being left to the discretion of
the operator.
Depress the LIFE TEST switch and allow a
few minutes for the tube heater tao stabilize,
Readjust the SET LINE control, if neces-
Pull down the Gm TEST ‘switch
ull down the Gr tch and
note the Gm reading. If this reading shows
more than 20% d drop relative to the Gm value
previously noted, it may be assumed that the
useful life of the tube is about over. Since
there is no positive method of determining
the remaining life of a vacuum tube, this
test provides you with only a "guestimate."”
A combination of your own experience,
knowledge of the particular circuit in which
the tube is used, and athorough understand-
ing of what the TT-1 is telling you, should
serve as an adequate guide in answering the
question, ''To replace or not to replace?”
sary.
a 4 3 tealnn f
these letters. This indicates the tube is a
multi gection type, two sections of which
may be tested with the same settings. Simply
move the indicated switches (P, G, K) to Po-
sition 2 and repeat the testing as outlined
above.
If there are two lines of control settings
listed for a single tube type, depress DIS-
CONNECT switch, change the control knobs
as indicated, and return the DISCONNECT
switch to the normal position. The tester is
—__—_ >
now set up for the second testtobe made on
this
tube.
ALWAYS
use
the
DISCONNECT
switch when changing settings with atube in
the tester, in order to avoid damage to the
tube under test,
The
above
instructions
are
intended
for
Gm
testing
of
amplifier
type
tubes.
Special
instruc-
tions
and
precautionary
notes
in
regard
to other
types
are
listed
below.
DIODE AND RECTIFIER TUBES
4
i.
Foliow
Steps
i
through
7,
as
listed
above.
NOTE:
The
SIG
and
BIAS
controls
have
no
effect
when
testing
rectifiers
or
diodes
and
may
therefore
be
in
any
position.
With
LEAKAGE
switch
in
the
TUBE
TEST
position,
depress
the
AMPL-RECT-DIODE
switch
to
the
RECT-DIODE
position.
If
a
D
appears
in
the
SIG
column
of
the
roll
chart,
a
meter
reading
above
the
DIODES
OK
mark
indicates
an
acceptable
tube.
If
an
R appears
in
the
SIG
column
of
the
roll
chart
the
meter
WORN RRNA NRE EER NR EES BEE UES by LEO LELO LUE
must
read
above
the
RECTIFIERS
OK
mark,
VOLTAGE REGULATOR (VR) TUBES
1.
Ih
oo
Refer to the roll chart for data on the tube
to be tested,
Set LEAKAGE switch to TUBE TEST posi-
tion, Set PLATE, FIL and SELE
ha 1
the ieieatee positions, Th
ayn, rarm
Turn the SET LINE controi fully counter-
clockwise and insert the tube in the proper
socket. Do not make a line check.
Turn the
pmo eh tne shi LINE Vues vu
rey
wiway
wise, observing the point o nm the 200 volt
taat mala at wht aan Lianne LE
tESt SCaie at which the tube 11205, When me
tube has fired, the pointer willfall backto a
lower value of voltage.
SET LINE eontrol
The value which the pointer reaches just be-
fore falling down-scale should be within the
firing limits, as snecified on the rolichart,
If the glow is not steady and/or the meter
pointer is not steady, the SET LINE control
should be increased (clockwise rotation)
just enough so that BOTH are steady. Ob-
serve the meter reading after this final
adjustment,
Page 11