The impedance at the "HIGH"
and "GND." pin jacks is
approximately 500,000
ohms. Some crystal type phono-
graph pick-ups
furnish
adequate
output voltage at
this load
impedance so as not to necessitate
pre-amplification.
This
assumes
that
no
corrective networks are
included in the
pick-up leads which would tend to reduce
the
voltage
out-
put. Magnetic pick-ups and
microphones especially,
require
previous stages
of
voltage
amplification, in order to bring
the signal up to a sufficient intensity to be
applied
to
the
"AUDIO SIGNAL"
terminals.
Because of the
presence
of a blocking condenser already
in series with
the
"HIGH" pin jack, direct connection
can
be
made from
this terminal to the plate
of any
voltage
am-
plifier employed, as long as the d.c. plate potential
DOES
NOT EXCEED ABOUT
350
VOLTS.
0-110 Numerical
Scale
and
Vernier
Segment
The
0-110
scale
along the
upper circumference of the
tuning
dial,
when employed in conjunction
with the
top vernier
plater
allows
for direct numerical readings
in
tenths of one division,
providing
1000 readable
points over
the
range of
0-100.
The
incorporation
of this numerical
reference
scale,
in addition to the direct
frequency cali-
brated
bands allows for maximum
^S^u^ajjy^jfijjss^uig.
lo
anv__.desired
Jr^qyency;
in other words,
it simplifies the
matter of returning
to
exactly
the same dial
spot when
occasions
demand it.
Another use of
the numerical
scale and vernier
is to
spot
special odd frequencies as may be
employed in govern-
ment,
commercial, aeronautical,
police, amateur
or experi-
mental services. In such
cases,
the E-200
is
tuneci
to zero-
beat
against
the exact frequency and the dial settings
taken
directly from the
numerical scale and
vernier. This
read-
ing can then
be
duplicated
at any time, as well as
re-
checked
with
the greatest of
ease.
When using the
0-110
scale, the ZERO LINE
of the vernier
plate becomes the
reference indicator instead of
the RED
hair-lines of the celluloid
pointers.
It
will
be noted
that the
10
divisions on the 0-10
vernier plate
are
ALWAYS
to
the right
of
the
0-110
dial
reading. Th
ese 10 vernier
di-
visions are
equal to
9
divisions
on the
0-110
scale, which
factor provides the vernier
action, that is, allows
for read-
ing the
numerical scale
in tenths of one
division. For
example:
—
Let
us assume that for some specific case, the
dial num-
ber under
the vernier ZERO reference
mark is somewhere
between
28 and 29.
Just
what that exact decimal
may be
is difficult
to
estimate.
The
vernier
plate simplifies
this
problem. Merely
look along
the
vernier
scale and
locate
that one division
of the
0-10
scale which
most
completely
coincides
(runs into) any one of the dial
divisions directly
below.
If
the seventh
line of
the
10 division
vernier
plate is
the
one, then
the decimal
is .7
and the
full reading
is then
28 plus
7/10
or 28.7.
One
and only one
vernier
division
can possibly
fully
coincide
at
a time
with a
dial division
except
for
the two
extremes
ZERO and
10. When
both
the
zero
and
10 coincide,
it
indicates
that
the
dial reading
under
the
zero
mark
is complete,
that
is
a
whole
number,
such as
29.0.
Therefore
according
to
the theory
of
the
vernier,
a number
can be
read (when
both
zero
and 10 are
coincident)
as either
29.0
or
28
plus
10/10,
which
are
mathematically
identical.
To reverse
the
procedure,
that
is,
to set
the dial accord-
ing
to
a given
numeral
(let us
assume
56.4
is desired),
merely
first set
the
dial
so that
the
nearest whole
number
(56.0)
falls under
the
zero
of
the vernier
plate.
Then
watch
the
4th
division
of the
vernier
plate
and slowly
ro-
tate the
dial towards
the
57 mark,
but stopping
as soon
as the
.4
line
on
the
vernier
plate
coincides
with
one of
the
dial
divisions
below
it.
This
will
occur before
the dial
reaches
the
57 mark.
Instrument
Service
It
will
be
noted that
in order to remove the E-200 from
its
metal carrying
case, it is necessary
to remove the 12
panel
border
screws and
then the
two
chassis
retaining
screws
at
the rear
of
m
the
^cabinet.
When removing
the
instrument
from
its housing,
extreme
care
should
be
exer-
cised
to prevent hitting
any
of the internal components
against
the
overlapping
mounting
surfaces
of the cabinet.
The
same should
be observed
when
placing the chassis back
into
the
cabinet.
If
at
any
time
this instrument
should fail
to
function
properly,
tubes should
always
be tested
first and
replace-
ment,
if necessary,
be made with
the exact same
type
NUMBERS.
If the instrument
does not function
at
all,
check the fuse
and when
required,
replace with
equivalent
type 1 ampere
type 3AG.
The schematic diagrams
included with this manual
may
prove
of assistance
in
the location of
possible simple diffi-
culties.
However, bear in mind that our factory service
division is
best
equipped to render efficient assistance in
the performance of
any and all repairs or adjustments.
Should it become necessary, at any time, to return your
E-200 or other Dynascan equipment for repair, recali-
bration or adjustment, same should be
carefully
packed
in
an oversized parton and forwarded via Railway
Express
Prepaid. This manner of handling will insure promptest
possible
and most
satisfactory service.
19
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