Advertisement
278-C
PAGE
TRK9, TRK90, TRKI2, TRKI20
A lignm ent Procedure
(RADIO CHASSIS)
Figure 29— A t Right— Tube and Trim m er Locations
Cathode-Ray Alignment is the preferable method.
Connections for the oscilloscope are shown in the
chassis drawing.
O utput M eter Alignment. — If this method is
, used, connect the meter across the voice coil, and
tu rn the receiver volume control to maximum.
Test-Oscillator. — For all alignment operations,-
connect the low side of the test'oscillator to the re'
ceiver chassis, and keep the output as low as pos'
sible to avoid a'V'C action.
Calibration Scale on Indicator-Drive-Cord Drum. — The
tuning dial is fastened in the cabinet and cannot be used for
reference- during alignment, therefore a calibration scale is at'
tached to the rear of the indicator'drive'cord drum which is
mounted on the front shaft of the gang condenser. The set'
ting of the gang condenser is read on this scale, which is
calibrated in degrees. T he correct setting of the gang in de'
grees, for each alignment frequency, is given in the align'
ment table.
As the first step in r-f alignment, check the position of the
drum. T he "O " mark on the drum scale must be vertical,
and directly over the center of the gang'condenser shaft when
the plates are fully meshed. The drum is held to the shaft by
means of two set screws, which must be tightened securely
when the drum is in the correct position.
Connect the high
Steps
side of test-
osc. to—
Turn fidelity switch to No. 3 radio (sharp).
1
6K7 2nd I-F grid
2
cap, in series
with .01 mfd.
6K7 1st I-F grid
cap, in series
3
with .01 mfd.
6A8 1st Det. grid
4
cap, in series
with .01 mfd.
Turn fidelity switch to No. 4 radio (broad). The curve on CRO should broaden out to a double peak and
6
reduce gain nearly 60%.
Turn fidelity switch to No. 3 radio for the following adjustments. Back out the "B" and "C" oscillator
6
trimmers, C6 and C4. Preset "A" band oscillator trimmer, C9, approximately an inch out.
7
Antenna
terminal, in
8
series with
100 mmf.
9
Repeat Step No. 8.
10
11
Antenna terminal,
in series with
§ 300 ohms
12
Follow "Adjustments for Electric Tuning.**
♦ Use minimum capacitance peak if two peaks can be obtained.
Note: T he oscillator tracks 455 kc above the signal on all bands.,
To determine the corresponding frequency for any setting
of the calibration scales, refer to the accompanying drawing
which shows the dial with O ' 180° calibration scales drawn
at top and bottom.
Pointer for Calibration Scale.— Improvise a pointer for the
calibration scale by fastening a piece of wire to the gang'
condenser frame, and bend the wire so that it points to tnie
" O " mark on the calibration scale when the plates are fully
meshed.
Dial-Indicator Adjustment.— After fastening the chassis in
the cabinet, attach the dial indicator to the drive cable with
indicator approximately 1/16'inch above end dots at low'
frequency ends of bands with gang condenser fully meshed.
See that pointer does not rub background screen or dial face.
The indicator has a spring clip for attachment to the cable.
Set tuning
Tunetest-
gang to—
osc. to—
Quiet
point
455 kc
on "B"
band
600 kc (31°)
600 kc
"A" band
1,500 kc (151°)
l,500kc
. "A" band .
600 kc
600 kc
"A" band
6,100 kc (140°)
6,100 kc
"B" band
20 me (146°)
20 me
"C" band
—
Figure 30—Alignment Procedure
Adjust the
To obtain—
following—
L15, L16
(3rd I-F Trans.)
Coincidental
images on
cathode-ray
L13, L14
oscilloscope,
(2nd I-F Trans.)
or max. out-
put on output
meter
LII, L12
(1st I-F Trans.)
L
(osc.)
Max. Output
10
CO (osc.)
C2 (ant.)
Max. Output
- C15 (det.)
Rock in for
L10 (osc.)
Max. Output
Max. Output*
C5 (osc.)
Rock in for
C4 (osc.)
Max. Output*
Advertisement
