Dynatuner FM-1 Istruzioni per il montaggio Operazione di allineamento - Pagina 14

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It is suggested that before proceeding, you read
these instructions over completely, to familiarize
yourself with the general procedure. The tuner is
to be connected to an amplifier and speaker, turned
on, and the antenna attached as for normal use.
I.F. Alignment
When making these adjustments, turn the slug
back and forth over a narrow range. Do it slowly
and carefully to obtain the correct point with
precision. If everything is normal, it is not necessary
to make more than a small adjustment to reach the
right point. I F YOU HA VE TO TURN PAST ONE
FULL TURN YOU ARE PROBABLY COM-
PENSATING FOR SOME FAULT IN WIRING
OR COMPONENTS, AND YOU SHOULD STOP
TO RECHECK BEFORE PROCEEDING. DO
NOT
APPLY
EXCESSIVE
FORCE
WHEN
TURNING THE SLUGS.
4
C....("
Set the tuning knob to a point where no station can
be heard (only hiss). Insert the plastic alignment
tool into the top of LF. transformer T4, and adjust
for the point of loudest hiss. If you find it difficult
to locate the peak, turning on a nearby vaCUUm
cleaner or electric shaver may simplify the task.
The sharpness of the point of correct tuning will
increase as you proceed. The hiss will get louder,
and you can control it for a comfortable level with
the volume control. As the adjustment proceeds,
some indication will become visible in the tuning
eye, and you will note that the eye closes to some
extent as the hiss increases. When this effect is
noted, you should make all further adjustments
using the maximum closing of the eye to tell you
what is the proper alignment point.
Always use the shoulder end of the alignment tool
for this work. The following 7 steps all refer to the
adjustment procedure described here.
5( V"Adjust the bottom slug of T4.
6(.;{
Adjust the top slug of T3.
7
(J'
Adjust the bottom slug of T3.
8(0 Adjust the top slug of T2.
9 ( Jdjust the bottom slug of T2.
10
(vt
fdjust the top slug of Tl.
11
(vf
Adjust the bottom slug of Tl.
Discriminator
Alignment
The alignment of the discriminator controls the
distortion of the entire tuner. The Dynatuner has a
positive adjustment technique for this critical part
of the alignment.
12( ) Tune a strong signal (station) very carefully to get
the precise point of maximum eye closing.
Make sure that you do not disturb the setting of the
tunin.g knob during the following adjustments, as it is
important for the tuner to be accurately tuned. The
eye will no longer indicate the exact tuning point, as
it will be serving other functions.
12
13( ) Unscrew (counter-clockwise) the top slug of the
discriminator transformer T5, using the shoulder end
of the plastic alignment tool. Unscrew this until the
top of the slug is flush with the top of the transformer.
This procedure has detuned the secondary winding
of the discriminator transformer-a step which is
essential in order to obtain the optimum adjustment
of its primary winding which is the next step.
At this point the tuning eye must be connected to
another part of the circuit in order to measure the
correct tuning point of the discriminator primary (as
set by the bottom slug). If you are care!ul, it is
possible to unsolder, and resolder the required wires
in this step and several succeeding steps without
turning off the tuner. However, YOU MUST
BE CONSCIOUS OF THE POSSIBLE SHOCK
HAZARD FROM THE EXPOSED WIRING. If
you wish to avoid all risk of shock, you can turn the
tuner off, make the connections, and turn it on again.
However, it is essential that you give the set a few
minutes to warm up thoroughly after any time that
you turn it off, even if the off-time is only a minute
or less.
Ie
11
VTVM is
ll ....
uiluble,
discl'iminntor
nlignlllent
tUIl
be simHlitled hy
following the
in~ll'uctiol'ls ~i\!en
in smull type. in place of :sleps }·1
throu,:rh 23.
The VTVM should be of a type which
hu~
at least n 1
me,whm resistor in the DC pr'obc to isolate the probe antl lead capacit.y
from the meuRured circuit.
Connect the VTVM between eyelet #32
Hl1d
the
ch1ts~is,
and
.Hljl.l:;t
the buttom
slu~
of T5 f01" maximulll ne).!nli .... e \'oltagoe (about
-~
volts L
Now connect the VTVM to eyelet #31. Tnrn the tOI) sin", of T5 in 9
full t.urns as n first appruximation.
Now adjust.. thh:i
tiIul<:"
:so
lh<lt
an
accurate z.ero reading is obtnined. It is
~sential
that
yOU KO
throu,sch
zero til'st. then locate
it
precisely. Use the
m~ximum
sensit,vity sc.·ale
on the meter.
14(
~
Unsolder and lift off the jumper wire which con-
. 7cts from eyelet #23 on PC-8 to eyelet B.
15(-1' Temporarily solder a wire from eyelet #23 to eyelet
#32 on PC-8.
l6( ...("Adjust the bottom slug
of
T5 for maximum closing
of the eye.
17(~
Unsolder the end of the temporary wire from eyelet
#32 and temporarily connect it to eyelet
113I.
l8(.I) Solder a 2" piec~ of bare wire to the center ground
yin of socket V7.
19(
0'
Turn the top slu!g of T5 in (clockwise)
9
full turns,
which brings it close to the proper adjustment point.
20(~Touch
the free end of the wire from the center
ground pin of V7 to eyelet #31. You will observe that
there is a deflection of the eye (either inward or
outward). Rotate the top slug of the discriminator
transformer T5 back and forth slowly while alter-
nately touching and releasing the free end of the wire
from the center ground pin of V7 to eyelet
1131.
The
actual adjustment of the slug must be made while
-------the wire is not touching the eyelet. Check the eye's
deflection after each change. You are seeking the
precise point where there is no shift in the eye as the
wire is touched to, and removed from, eyelet #3I.
There may be slight changes in the brightness of the
eye as this is done, but these are of no consequence.
Turn the slug in the direction which minimizes the
shift in deflection until there is no shift when the
wire makes or breaks contact with eyelet
/131.
21 (
\Y
Remove the temporary wire between eyelets #23 and
#31.
22 (
III
Re-coJU1ect the jumper wire from eyelet #23 to
eyelet B. Keep it reasonably close to the board.