Heathkit TT-1 - Page 5

LINE TEST CIRCUIT
The line test circuit is in operation when the
line test switch is inthe "down" position. Chang-
ing the position of thet tap on tha
primary of the power transformer (rotating the
SET LINE control) will, in effect, vary the turns
ratio. The voltage across each of the four sec-
ondary windings will change simultaneously as
the SET LINE control is varied. Therefore,
adjusting one particular winding to the proper
level automatically sets the voltage of all sec-
ondary windings to a specified value.
anntroal
LEAKAGE TEST CIRCUIT
Leakage testing is controlled by the LEAKAGE
Switch which, in its numbered positions, dis-
connects all tube elements from the other testing
circuits and connects them into the leakage test
circuit. The meter deflection in each switch po-
sition is indicative of the resistance between the
isolated element and other elements of the tube.
R26
105-125 = —_
VAG
For
this
circuit
the
meter
deflection
is
inversely
proportional
to
the
leakage
resistance,
a
full-
scale
reading
thus
indicating
zero
resistance.
Resistance
values
as
high
as
10
megohms
can
be
measured.
The
element
checked
for
a
given
position
of
the
LEAKAGE
switch
is
shown
below.
Tk
TO
ELEMENTS
UNDER
TEST
POSITION
MEASURES
LEAKAGE
BETWEEN
1
Heater
and
cathode.
2
Suppressor
grid
and
all
other
elements.
3
Plate
and
all
other
elements.
4
Screen
grid
and
all
other
elements.
5
Control
grid
and
all
other
elements.
ndicationfor
ition
1
hort
test
circui
t
is normal “for es that are of the filamentary
type or have an n internal heater-cathode con-
nection.
The red line on the leakage scale is the 250,000
ohms mark and is the approximate value that
causes the neon lamp to light in conventional
The leakage tests are performed at a DC poten-
tial of 125 volts. The element under testis con-
nected into a series ohmmeter circuit as shown
in the Diagram. Any deflection of the meter will
be proportional to the value of resistance placed
between the arrows,
Page 5
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