Alignment procedure

a. Preliminary Setup: Adjust the signal generator to approximately 155 ke and connect it» output to the control grid cap of the 1st detector tube (V3) through a fixed capacitor (anything larger than 100 nnnf will do). Set the front panel controls as follows:

SENSITIVITY > 0

WC-MAMAl MANUAL

signal-mod-cw mod

SEND-REC REC

BAND SWITCH 2.85-6.3 mc

AUDIO GAIN 10

CRYSTAL SELECTIVITY OFF

PHASING on arrow

BAND WIDTH 3

BAND SPREAD D1AI 100

b. IF Alignment Check:

(1) Set the MAIN TUNING dial near 2.85 mc, but be careful not to tune in a powerful local signal. Set the CRYSTAL SELECTIVITY switch on 3, the AVC-MANUAL switch on AVC, and advance the SENSITIVITY to 10. Turn off the modulation of the signal generator and adjust its frequency slightly to produce maximum deflection of the "S" meter. The adjustment of the signal generator in this manner is necessary in order to get exact agreement with the natural period of the particular quart/, crystal in the Receiver being checked. After reducing SENSITIVITY to 0, the modulation may be switch on, but the tuning adjustment of the signal generator must not be altered until the alignment check has been completed. Return the CRYSTAL SELECTIVITY and AVC-M \NUAL controls to their original Meltings of OFF and MANUAL and advance the SENSITIVITY control until a suitable output meter reading is obtained. A half-scale reading in the region of 5 to 10 volts will be satisfactory.

(2) Now check the alignment of both upper (grid) and lower (plate) air trimmer capacitors in Ip transformers T2 and T3 and the single trimmer in T4 for peak reading of the output meter. If one or more of these adjustments results in a sizeable increase in output, reduce the SENSITIVITY control enough to bring the meter reading back to half-scale. Alignment of the plate circuit of the crystal filter (T1) can be tested in the same way by means of the lower adjusting screw on the side of the unit. This screw varies the position of the powdered iron core in coil 1.26. Do not change the setting of the upper adjusting screw which tunes grid coil L27, as this circuit cannot be adjusted properly with the output meter. It can, however, be aligned by the "visual" method using a frequency-modulated signal generator »ml cathode-ray oscilloscope. 11' this e<|iiipinent is available, proceed as follows:

(3 )Connect the input of the vertical amplifier of the oscilloscope to the. PlIOIS'O connections on Terminal strip E3 I Ftc. 7) on the rear skirt of the Receiver chassis. The "high" terminal is the second one from the edge of the strip; the first screw is connected to the chassis. Set the frequency-modulated signal generator to approximately 155 ke and connect its output to the control grid cap of the 1st detector (V3) through a fixed capacitor (100 nimf or larger). With the CRYSTAL SELECTIVITY switch at OFF, readjust the signal generator frequency to produce the conventional single-peaked resonance curve on the screen of the oscilloscope. Then turn the CRYSTAL SELECTIVITY switch, to position 1. If the grid coil (L27) is correctly tuned the image on the oscilloscope screen will remain symmetrical but will be only about two-thirds as wide as before, indicating an increase in selectivity. The oscilloscope image is also affected by the PHASING control, maximum symmetry occurring at or very near the arrow on its scale. Therefore, when tuning 1-27, rock the PHASING control back and forth at the same time to secure the best adjustment.

e. AVC Alignment Check: leaving all other controls as in Par. 26a, and without changing the signal generator frequency, reduce AUDIO GAIN to 0, switch to AVC and increase SENSITIVITY to 10. Increase AUDIO GAIN to restore half-scale reading on the output meter and adjust the single trimmer capacitor in T6 for minimum output meter reading. The "SM meter reading should "peak" at the same time the output meter reading "dips."

d. Beat Oscillator Alignment Check: Continuing with controls as above (Par. 26c), switch off the output meter and plug in a pair of earphones, or replace the meter with a suitable loudspeaker. Turn the SIGNAL-MOD-CW «witch to CW and see that the BEAT OSCILLATOR control is exactly on 0 (zero). If tone in earphones or speaker is not very low in pitch, readjust the trimmer capacitor near the bottom of T5 until it is. If the beat oscillator is in perfect alignment when this test is made, no sound will be heard since the signal generator and tin- beat oscillator will be oscillating at the same frequency and there will be no audible differncc or "beat." Check this by turning the BEAT OSCILLATOR control knob slightly off 0 (zero) toward one side or the other. If this results in a tone rising in pitch as the pointer is turned away from 0 (zero) to either side, the beat frequency oscillator is perfectly aligned. If no audible tone can be obtained within the range of the BEAT OSCILLATOR control, adjust the trimmer capacitor near the bottom of T5 until an approximate "zero beat" occurs at 0 (zero) setting of the BEAT OSCILLATOR control.

e. HF Oscillator Calibration Check: The accuracy of the MAIN DIAL calibration depends solely on the HF oscillator frequency, which in this Receiver is 155 kc. (the IF) higher than the signal frequency. Although the frequency of the HF oscillator can be measured directly if accurate frequency-measuring equipment is on hand, it is far simpler to check it by tuning in signals of known frequency ami noting the MAIN DIAL readings. Caution: Bk sure ttie band spread dial is sirr at 1(h) when making this test.

ll) To correct dial calibration, refer to alignment chart (Flo. 13) for location of HF oscillator adjustments as well as signal frequencies at which settings should be made. The output of the signal generator should be unmodulated and S1GNAL-MOD-CW switch on Receiver turned to CW. Set BEAT OSCILLATOR at 0, AUDIO GAIN at 10, A YC-MANUAL on MANUAL, BAND WIDTH at 16. Disconnect output meter and use earphones or loudspeaker to make necessary adjustments by "zero heat" method. Connect signal generator to antenna terminals for this test. •

(2> If the 2.85-6.3 mc hand is to be corrected, tune signal generator accurately to 6.3 mc. Tune in signal generator signal at 6.3 mc end of Receiver dial to zero beat. Notice approximate dial error. Turn main dial slightly toward 6.3 mc calibration line until beat note rises to a high pitch. Do not turn dial far enough to raise beat so high it cannot be heard. With alignment screwdriver adjust trimmer capacitor marked IIF OSC 6.3 mc (Fig. 13) until beat is again zero. Turn main dial still farther toward 6 3 mc line and makr a further adjustment of trimmer capacitor to return to zero beat. Repeat this process as often as necessary to bring dial to exactly 6.3 inc. (The main dial could be set at once on exactly 6.3 mc ami trimmer turned enough at one time to produce zero beat, but the step-by-step method is recommended.) Now retune signal generator to exactly 2.85 mc and tune in signal-generator signal at low-frequency end of main dial and correct the calibration step-by-step as before, using inductance trimming adjustment HF OSC 2.85 me (Fig. 13). When 6.3 mc signal from signal generator is again tuned in at other end of dial, it will be found that inductance adjustment at 2.85 mc has changed correction previously made at 6.3 mc. This is normal. Go back and forth several times from 2.85 to 6.3 mc in order to bring both ends of dial scale into exact agreement with the signal frequency. Caution: During this adjustment be very careful to adjust the sensitivity control to \void overloading.

f. HF and 1st Detector Alignment Check: Although alignment of these three circuits (1st and 2nd RF and 1st Del) can be checked at the same time as the HF oscillator, it is simpler to consider each check

as a separate operation. Efficient weak-signal reception, with low receiver noise level and high image rejection ratios, depends on the relative alignment of these three circuits with respect to the HF oscillator and without regard to calibration accuracy.

11) Accurate calibration of the signal generator is not required to cheek these adjustments. Modulation of the signal generator, while convenient, is not strictly necessary. Input to antenna terminals should be through 100 ohms (approximate) including output resistance of signal generator. If signal generator is modulated. Receiver controls should be set as for IF alignment; if unmodulated, set BEAT OSCILLATOR to 2 (either side I and SIG.NAL-MOD-CW to CW. Adjust SENSITIVITY for half-scale reading on output meter when signals are exactly in tunc.

(2) Starting with 2.85*6.3 me band, set main dial at 6.3 me (BAND SPREAD at 1(M)I and adjust frequency of signal generator for peak deflection «if output meter. Then check setting of trimmer marked 1st DET 6.3 me i Fig. 13). Repeat this procedure on trimmers designated as 2nd RF and 1st RF in same row. If readjustments on one of these settings greatly increases output meter reading, alter SENSITIVITY slightly to reduce reading to half-scale. After each adjustment check tuning of Receiver to make sure test signal is still accurately tuned. BAND SPREAD may be-used as a vernier for this purpose.

Caution: This tuning check is extremely important at high end of 6 3-14.0 MC and 13.4-30.0 MC bands where there is some slight interaction between 1ST DET and HF OSC circuits. After cheeking the three trimmers at high end of this hand, turn main dial to 2.8!» mc ami rctunc signal generator to suit. Then check the three inductance adjuster settings marked 2.85 mc (FlC. 13) in the same row. Since adjustments at one end of a band also affect the other end of the hand 4as described under IIF OSC alignment), repeat above procedure until no further improvement can be secured. The number of repetitions necessary depends on how much mistiming existed initially. Other hands may be checked in the same manner.

(3) For best possible efficiency with a particular antenna arrangement, the 1st RF circuits may be adjusted with the antenna connected. This can be «lone by loosely coupling output of signal generator to antenna system instead of directly to antenna terminals through a 100-ohm resistor. Make sure that signal from signal generator actually reaches Receiver by way of antenna rather than by some form of direct coupling.

(4) In all the foregoing tests using output meter readings for circuit adjustment it is recommended that earphones (or speaker) be used to monitor the signal. This will avoid false adjustments caused by overloading or freakish responses.

Circuit Rkh. No.

CAPACITORS Main Tuning Band Spread 620 imnf, Mira .02 mf. Paper

Trimmer. Mica, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer. Mira, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer, Mira. 3-30 mmf Trimmer. Mica. 3-30 mmf Trimmer. Mira. 3-30 mmf Trimmer. Mira, 3-30 mmf Trimmer. Mira, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer, Mira. 3-30 mmf Trimmer, Mica, 3-30 mmf Trimmer, Mira, 3-30 mmf Trimmer, Air. 4-25 mmf Trimmer, Air, 4-25 mmf ' Trimmer, Air. 4-25 mmf Trimmer, Air. 4-25 mmf Trimmer, Air, 4*25 mmf 31H) mmf. Silver Mira 620 mmf. Mira .02 mf. Puper . .05 mf. Paper 3(HJ mmf. Silvered Mira : 620 mmf. Mira .02 mf. Paper .05 mf. Paper 95 mmf. Silvered Mira 673 mmf. Silvered Mira 1500 mmf. Silvered Mira 3300 mmf. Silvered Mira 300 mmf, Silvered Mica. 51 mmf. Silvered Mira .05 mf. Paper .05 mf. Paper 120 mmf. Silvered Mica 101) mmf. Mica KM) mmf. Mica NOT USED

•imiij:. Air. 2-6 mmf <ea.) .02 mf. Paper . . 85 mmf. Silvered Mica, 2% .05 mf. Paper Variable. Air. 100 imnf .05 mf. Paper .05 mf. Paper Variable, Air, 100 mmf

Variable, Air, 100 mmf .05 mf. Paper . j .05 mf. Piper I Variable. Air. 100 mmf

Part of Part of Part of Part of Part of Part of Part ..f Part of Part of Part of Part of Part of Part of Part of Parí of Part of Part of Part of Part of Part of

29529-01

29532-01

29538-G1

29520-01 29535-Cl

29530-G1

29533-01

29539-01

29521-OI 295364Í1 295304;1 295334;1 29539-G1 295214; 1 295364;1 295314;1

29534-G1 295404;1 29528-G1 29537-01

Part of 29531-01 Part of 295344; I Part of 295374;! Part of 295284Í1

Puir No.

23005-86

23912-1

23912-2

23003-105D

23005416

23912-1

23912-2

23003-1051)

23005-86

23912 1

23912-2

6195

231)03-50

23912-2

23912-2

23003-96

23001-18

23001-48

SA-179

23912-1

61B0

23912-2

SA-1

23912-2

23912-2

SA-1

23912-2

SA-1

23912-2

23912-2

SA-1

Description

CAPACITORS Continued

5 mnif. Silvered Mica Variable. Air. 100 mmf

.05 mf. Paper 51 mmf. Mira Variable. Air. 100 mmf 100 mmf. Mica Variable Air, 9 mmf 95 mmf. Silvered Mica

Variable. Air. 100 mmf 5100 mmf. Mini .05 mf. Paper .05 mf. Paper .05 mf. Paper .05 mf. Paper 05 mf. Paper .02 mf. Paper

•40 mf. Flectrolytic, Dry

Part No.

COILS

Assembly, Assembly, Assembly, Assembly, Assembly. Not Used Not Used Not Used Not Used Not Used

Assembly. Assembly, Assembly, Assembly. Assembly, Assembly, Assembly, Assembly, Assembly, Assembly, Assembly, Assembly, Assembly. Assembly, As>embly, Universal, Universal, 3 pie univ

Antenna transformer. 1.24-2.86 me Antenna transformer. 2.85-6.3 me Antenna transformer. 13.4-30.0 me Antenna transformer, 540-1240 ke Antenna transformer, 6.3-14.0 mc

R.F. transformer, 1,24-2.86 mc R.F. transformer, 2.85-6.3 me R.F'. transformer, 13.4-30.0 mc R.F. transformed 540-1240 ke R.F. transformer, 6.3-14.0 mc

Same as Lll

Same as LI3

Same as LI5

Oscillator Coil. 1.24-2.86 mc Oscillator Coil, 2.85-6.3 mc Oscillator Coil. 13.4-30.0 mc Oscillator Coil, 540-1240 kc Oscillator Coil, 6.3-14.0 me 7/41 Litz., iron dust core 7/41 Liti., iron dust core ersal 7/41 Litz„ ceramic corc .

Description

COU.S Continued

3 pie universal 7/41 I.it*., ceramic coil

Universal, 7/41 Liu., ceramic core v

3 pie universal 7/41 Litz., ceramic coil

Universal, 7/41 l.ilz., ceramic core

Choke Coil, 5 pie universal R.F. choke, ceramic core, wire leads <. ..

Choke Coil, Same as L35

JACK, JK-34 A, Phone Jack Iheudtet) Meier, 0-200 micro-ampere movement

RESISTORS

500,000 ohms, W 10,000 ohms, V2 W 50,000 ohms. V» W 2 UM10 ohms. 2 W 50.0H0 ohms. % W 12.000 ohms. 2 W 2.ft»» ohms, Vi W 10,000 ohms. W ¿1 ohms. % W 51 ohms, Vi W 300 ohms 'Vt W

2,000 ohm», >/2 W 2.000 ohms. Va W 10,000 ohm'v. 1/i w

2.000 ohms. % W 10,000 ohms W 51,000 ohms, 1 W 2,000 ohms, V4 W lOO.OQO ohms, V2 W 75,000 'oluns. Vi W S1,000 ohms 'A w

240,000 ohms, V4 W

4 ohms. 5 W 100.001» ohms. V4 W 510,000 ohms '/s W 5,100 ohms V4 W 51.000 ohms V4 w

1,000 ohm». Potentiometer 2,000 ohms Î4 W 24.000 ohms, % W 10,000 ohms Vt W

1 Megohm. V4 W

CmcuiT

Description

Part No.

RKK. No.

RESISTORS -Continued

R46

50.000 ohms, Potentiometer

5023

R47

4 ohm«, 5 W

194311

R48

250.000 ohm». Potentiometer

4919

R49

510.000 ohnu, U W >*

19309-159

R50

300 oknu, V2 w ..

19301-196

RS1

1.800 ohm*. V2 w

19301-38

R52

3.000 ohm», 1 W

19303-169

R53

51,000 ohm», 1 W

19303-182

R54

510,000 ohms. V4 W

19309-159

R55

750 ohms 10 W

19430-30

Sit ITCHES

S1

10 pole. 5 position, 5 section

S2

Wafer type, 6 position -

4911

S3

SPST rotary snap

4916

S4

DPST rotary snap

5733

S5

DPST toggle

2990

S6

SPST rotary snap

5729

S7

DPST toggle ...

2983-1

TRANSFORMERS

T1

Filler Assembly, Variable selectivity quart* crystal filter

29555-G1

T2

Variable selectivity I.F. transformer

SA-166A

TS

Same as T2

SA-166A

T4

Fixed selectivity, I.F. transformer

SA-167A

T5

455 kc oscillator assembly

SA-169A

T6

Fixed selectivity, I.F. transformer

SA-168A

T7

A.F. transformer, push-pull input

4887

T8

A.F. transformer, push-pull output

4888

TIRES .

VI. V2. VS

6K7 /

16244-1

V3

6L7 .

10212-1

V4

6J7 -j , :

16220-1

V6. VT, Vll

6SK7 ..

16245-1

V8. VI2

6H6

16202-1

V9

6N7 *

16246-1

V10

6SJ7 »

16236-1

V13

6J5

16209-1

V14.V1S.V16

6F6

16239-1

WI

Connector Cable. Nine wire, with two 10 terminal

SA-35

connector strips

W2

Connector Cable, Fight M'ire, with one 10 terminal

SA-67

connector strip (special order only)

X1-X4

Tube Socket, Molded octal. low-Ioss bake] ite

16082-1

X5-X16

Tube Sockct, Molded octal, black bakelite

16083-1

Y1

Quartz Crystal, Resonator type, ground for 455 kc

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