The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1925-08-28

That was L1L2. Now wind L3L4
exactly the same way, except that
when you reach the fortieth turn pick
up ten feet of the same kind Of wire
and wind this as II it were a special
primary, side by side with the con-
tinued secondary, then go it alone with.
the secondary to the end Now you
have L3L4L5.
The aerial transformer Is connected
so that the adjacent terminals (hub,
end OF primary and hub end of sec
ondary) go to ground and minus A re-
spectively. The hub side, that Is, in
side terminal, OF L3 goes to B plus
67h volts, and this B battery should
be separate one for best results, al
though the set will work well on q.
common B battery block The minus
of this 67A-volt block, by the way,
goes to plus A, too.
The terminal of the secondary, LA,
that goes to the grid condenser, Is the
end at the outside diameter, while the
outside terminal of L5 goes to plate.
The circuit diagram shows how the
| condensers are connected to these
coils. The ticker, L5, is not rotable,
| Of course, and that explains why it Is
possible TO chart the regeneration con-
| troll
Both audio tubes have grids biased
Az volts negative. This usually means
the three-volt post of a standard G
battery will be used as the nearest
approach, if the exact Az volts aren't
| accessible. There is a one-vOlt mega
tive bias impaired by the grid return
to minus A (say, six volts at this
/ poinD, as compared with the FIVE volts
at the other side of the rheOstat fla
ment minus. whence all voltage reck-
oning proceeds. Indeed, the drop in
the rheostat may be little more than
volt. Hence, only three extra or ex-
ternal volts are needed.
In figuring the plate pOtentiaIs, the
common lead, A plus and B minus.
must be counted, too, as adding the
voltage of the A battery to that OF
the battery at the plate. The series
connection is obvious-minus six TO
plus six Is six volts, hence with B
minus connected here you start off
with premium of six volts A 221h-
volt tap off the B battery would real
ly be 2S1a volts These allowances
must be made, especially when using
tubes that are critical as to plate volt
age, especially the C-30O and UV-2OO,
the most sensitive detector tubes
known, though they do draw one
whole undisputed ampere
Audio Hook-Up Is Standard.
The audio hook-up is standard, ex-
cept for the filament control Jack.
Those not familiar with it's operation
will see from the diagram that adjoin-
ing springs of the jack are connected
respectively to B plus and plate.
When the plug is inserted it pushes
up the springy leaf already connected,
as the other one is the very stiff
frame. Notice that there is piece Of
insulation between the plate spring
and the adjoining one above It, This
is both the safeguard against short
circuit and the lever used to close the
filament circuit. II will be seen that
the otherwise continuous filament
minus lead-in is interrupted by being
passed from detector tube to the sec
Ond spring from top. in F. c. J.. The
switch S may be used for turning the
set on and off as a unit.
AS the three amplifier tubes-one
radio and two audio-are operated
from one control, it should be power
rheostat, if wire-bound. otherwise one
of the compression or decomposition
type. The ordinary run of rheOstat.
ohms will heat up Under this heavy
current.
A double-circuit jack ] Is used In
the first audio output. as this is a
good place to listen to DIX stations in
winter (and in summer, when. If and
where possible), and provides sufi-
cient speaker volume from some To-
calls. The change from first to second
audio output is made simply by pulling
the plug out Of the one Jack and in
sorting it in the filament control lack.
which lights the last audio tube and
taps plate and B plus.
The C-301A and UV-2O1A tubes are
best for this circuit. although any of
the dry cell tubes may be used TO ex,
cellent advantage.