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ALIGNMENT PROCEDURE
There are various alignment trimmers provided in the detector
and oscillator coil tuned circuits. The i -f transformer adjustments
are made by means of screws attached to molded magnetite cores.
411 of these circuits have been accurately adjusted during manu-
facture and should remain properly aligned unless affected by
abnormal conditions or altered during servicing.
Loss of sens-
itivity, improper tone quality, and poor selectivity are the usual
indications of improper alignment.
The correct performance of this receiver can only be obtained
when the aligning has been done with adequate and reliable
apparatus.
It is not necessary to use a frequency modulated
oscillator and cathode ray oscillograph to align this receiver.
Those service men that have this equipment will probably prefer
to use it and for their convenience we have indicated on the
trimmer location diagram the proper connection point for the
cathode ray vertical amplifier input terminal.
A test oscillator is required as a source of the specified align-
ment frequencies. Visual indication of receiver output during the
adjustment is necessary and should be accomplished by the use
of an indicator or meter.
The procedure outlined below should be followed in adjusting
the various trimmer capacitors and molded cores:
Calibrate the tuning dial by adjusting pointer to the low
frequency end of scale with gang condenser plates fully meshed.
The pointer may be adjusted along the phosphor bronze drive
cable by slackening the stud which secures the glider to the phos-
phor bronze drive cable.
Perform alignment in proper order as shown by the accom-
panying chart, starting with No. 1, and following all operations
across, then No. 2, etc. The chassis bottom shield must be
securely in place when making R.F. adjustments. Adjustment
locations and fequencies are shown on a sticker fastened to the
bottom side of the chassis shield. These trimmer locations are
also shown in one of the accompanying illustrations.
Connect the "low" output terminal of the test oscillator to the
receiver chassis for all alignment operations. Regulate the output
of the test oscillator so that minimum signal is applied to the
receiver to obtain an observable output indication.
This will
avoid a -v -c action.
The term "Dummy antenna" means the device which must be
connected between the "high" test oscillator output terminal and
the point of connection to the receiver in order to obtain ideal
alignment.
"No signal, 550-750 kc." means that the receiver
should be tuned to a point between 550 and 750 kc. where no
signal or interfrence is received from a station or the receiver
(heterodyne) oscillator.
The term "Rock Through" indicates that the receiver station
selector should be rocked back and forth while making the
indicated adjustment. The adjustment and rocking should be
continued until the combined action results in the maximum
deflection on the output meter.
When adjusting oscillator circuits that nave both series and
shunt trimmers it is good practice to repeat the adjustment on
the oscillator shunt trimmer after making the adjustment on the
oscillator series trimmer.
When calibrating the short wave "spread" bands (see operat-
ions 6, 9, 10 and 11 in the Alignment Chart), it is necessary to
have a very accurate source of test signal. As there are no service
oscillators available at present with sufficient accuracy for this
calibration adjustment, it is recommended that the respective
adjustments to L-16, L-17, L-15 and C-8 be made while listening
to a short wave broadcast station of known frequency, approxim-
ately in the middle of the band being calibrated.
Operations
7 and 8 may be performed after operation 6 by setting the re-
ceiver to 11,800 kc. and tuning the test oscillator to the receiver
PRECAUTIONARY LEAD DRESS-(1) All bare bus leads
adjacent to the R.F. coils or Range Selector Switch should be
as short and direct as possible.
(2)
All insulated leads adjacent to the R.F. coils should be
dressed away from the coils.
(3)
Heater leads should be tightly twisted together and dressed
away from grid leads of audio tubes to avoid hum pick-up.
(4)
Leads connected to phonograph pick-up terminal should
be tightly twisted together and dressed close to chassis frame.
(5)
Power output stage grid leads should be dressed away from
the high voltage secondary winding leads of power transformer t'.
avoid hum pick-up.
ALIGNMENT CHART
Order of
Align-
ment
Connection
To Receiver
Test Oscillator
Dummy
Antenna
Frequency
Setting
Receiver
Dial and
Range Setting
Master-
Manual Sw.
Position
Circuit
To Adjust
Adjust-
ment
Symbols
Adjust to
Obtain
1.
Turn this screw all the way out.
A.F.C. I.F.
L 26
2.
Check with mechanic's scale. This screw should protrude exactly % inch.
A.F.C. I.F.
L 25
3
W -6K7 I.F.
Grid Cap
.001 Mfd.
460 kc.
No signal
550-750 kc.
Manual
2nd. I.F.
Transf.
L23, L24
Max. (Peak)
4
W -6L7
First Det.
.001 Mfd.
460 kc.
No Signal
550-750 kc.
Manual
1st. I.F.
Transf.
L21, L22
Max.(Peak)
5
W -6L7
First Det.
.001 Mfd.
460 kc.
No Signal
550-750 kc.
Manual
.. 2nd. I.F.
Transf.
L23, L24
Max (Peak)
6
Ant. Term.
400 ohms
11,800 kc.
11,800 kc.
Manual
Osc. 25M.
L16
Max (Peak )t
7
Ant. Term.
400 ohms
11,800 kc.
11,800 kc.
Manual
Det. 25M.
C19
Max (Peak)**
8
Ant. Term.
400 ohms
11,800 kc.
11,800 kc.
Manual
Ant. 25M.
C3
Max (Peak)**
9
Ant. Term.
400 ohms
9,600 kc.
9,600 kc.
Manual
Osc. 31M.
L17
Max (Peak )f
10
Ant. Term.
400 ohms
15,200 kc.
15,200 kc.
Manual
Osc. 19M.
L15
Max (Peak )t
11
Ant. Term.
400 ohms
6,100 kc.
6,100 kc.
Manual
Ose. 49M.
C8
Max (Peak)*
12
Ant. Term.
200 mmfd.
1,500 kc.
1,500 kc.
Manual
B.C. H.F. Osc.
C25
Max (Peak)**
13
Ant. Term.
200 mmfd.
600 kc.
Rock Through
600 kc.
Manual
B.C. L.F. Ose.
L20
Max (Peak)
14
Repeat 12
15
Repeat 13
16
Repeat 12
17
See instructions below for A.F.C. Alignment
L26.
* If two peaks obtainable use higher capacity setting.
t If two peaks obtainable use lower inductance setting (screw fur-
** If two peaks obtainable use lower capacity setting.
ther out).
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