Heathkit IM-16 - Page 29

(
)
Strip
l/2"
of
insulation from both ends
of
the
black
test
lead.
(
)
Unscrew
the
cap
from
the
phone
plug.
(
)
Insert the test lead cable
andthefree
end
of
the
shielded cable
through
the
phone
plug
cap.
(
)
Now twist the shield
wires
of
the shielded
cable
and
the wires at
the end
of
the
black
test
lead firmly
together
and
melt a small
amount of solder
on
the
combined
wires
as
shown
in
Detail 13G.
Also
melt
a small
amount
of
solder
on
the inner conducting
wire
of
the shielded cab1e.
Take
care
notto
melt
the inner
insulation.
In the
following step,
you
will connect
the
pre-
pared
cables
to the
phone
plug
as
shown
in
Detail
13G.
To avoid
cirverheating
the
cable insu-
lation,
first
apply a film
of
solder
to the
phone
plug
terminals and heat
thoroughly; thenholdthe
wires
to the
phone
plug
and apply
just
enough
heat
to melt the solder"
(
)
Refer to Detail
13G
and
solder
the two
twisted wires
to the
phone
plug.
Be
careful
not to melt
or
burn
the inner
plastic
insu-
lation
of
the
shielded cable.
Thensolderthe
inner
wire of
the
shielded
cable
as
shown.
Detqil
l3G
Be sure the
phone plug
body
will
still fit
over
the
wires. Use
onlyenoughheattomelt
tfie
solder
and
make a
good
connection.
(
)
After
the
wires
have
completely
cooled, use
pliers
to
bend
the tabs
on
the
phone plug
over lightly
to
secure the
black
cable.
Then
screw
the
cap onto
the
phone
plug.
(
)
Melt
a
small amount
of solder on
the
strands
of
the
free
end of
the
black
test
lead
and
solder it-to the alligator
clip
as
shown.
This
completes
the
phone plug
assembly.
CALIBRATION
Three
internal
adjustments
are
'required
to
calibrate
the Solid-State
Voltmeter.
These ad-
justments
are:
Bias,
DC Cal, and
AC
Cal,
The
Bias adjustment
provides the
correct
DC
gate
voltage
to
the
field
effect
transistor,
while the
DC
Cal
and
AC Cal adjust
the sensitivity
of
the
circuit.
The
calibration
of
your
Voltmeter must be
done
carefully
and accurately,
since
these
adjust-
ments determine
the overall
accuracy of
the
instrument. Refer to
Figures
1
and 2
(fold-out
from
Page
25) for location of
the
adjustments,
controls,
and
switches"
ff at
any time
you
do not
obtainthe
results indi-
cated
in
a
step,
refer
tothelnCase Of
Difficulty
section on
Page
30"
Locate
and repairanyprob-
lem
before
you
continue
with
the
adjustments.
BIAS ADJUST[,lENT
(
)
Turn the three internal controls
(AC
Cal,
DC Cal, and Bias) fully counterclockwise.
(
)
Set the
front
panel
switches and
controlsas
follows:
VOLTS
switch"
"
.fully
counterclockwise
OHMS switch.
,
"
"fully
counterclockwise
OHMS
ADJUST
controln
.fully
counterclock-
wise"
POVIER
switch.
. .OFF
FUNCTION
switch.
.
.DC+
ZERO ADJUST
control.
. .centerof
rotation
(See
the following
Note.)
NOTE: The
OHMS
ADJUST
and
ZERO ADJUST
controls
have
lO-turn
planetary
drives"
To
set
the
ZERO
ADJUST
control
to the
center of
its