Noblitt-Sparks Industries, Inc. 351P Schematic

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Product Information:
Model:351P
Manufacturer:Noblitt-Sparks Industries, Inc. (Arvin)
Description:RE-267

Schematics Content:

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Page 1:

NoBLlTT-sPARKS PAGE 20-7
MODELS 350P, I'

81/2 TURNS

DIAL STRI N GI NG A RRAN GEM E N T SPECIFICATIONS

FREQUENCY RANGE LOUD SPEAKER
Broadcast _ _ 540 1600 ke Type; Permanent magnet
IF kc Size: 4 Inch
Tuegi QFD FUNCTIONS _______ RF Amp* Voice coil impedance ____________________ 3.2 Ohms
_ Mixer-facillatm CHASSIS FEATURES
1U5 _ _ DET_AVC AF Amp- gutlomatrc Volume Control
POWER suPPLY n e e '
1. 2:0 B Battery, Eveready Minimax, No. 490 or OPERATING CONTROLS
qua . _ __ _ _
6. 1% V. C Size Flashlight Cells, 9 Volts total llr'iegfinkxigsb _ >_911_S)_ff_5_`j_ft_
Or 115 Volts AC or DC, 16 Watts _
POWER OUTPUT PHYSICAL DIMENSIONS
Undistorted _ - .2 Watt Length _ __ 91/1 inches
Maximum _ .3 Watt Height _ 71/2 inches
Plate Load _. _ 10,000 ohms Depth _ _ 4% inches
Models 3501' Bl 3511? are identical except for the Color of the Cabinet and Dial Backing plate, Model 3501' is Blue Green,
Model 8511' is lade ALIGNMENT PROCEDURE

Connect to 117 V. AC line and turn set on with volume control at full volume,

Br Colnpect output meter across speaker voice coil. (Output meter reading to indicate 50 MW, standard output is .4

With variable condenser closed set pointer to end mark, (bottom hole) on dial back.

D. Connect signal generator high side through .05 uf or larger condenser to high side of loop or variable condenser.
Connect signal generator low side to floating ground ofthe receiver.

E. Open variable condenser.

F. With signal generator set at 455 Kc., increase output of generator until output is heard in speaker. Adjust I. F.
trimmers A1, A2, A3 and A4 until maximum output ineter reading is obtained, reducing signal generator output as
adjustment progresses so that final adjustment is made with lowest input consistent with good signal to noise ratioV
NOTE: If no signal can be heard with signal generator connected at at D above, connect high side to terminal 6
of IHS tube, through condenser as at D, and proceed as before.

G. With signal generator at 455 Kc and connected as in D above, adjust R. F, transformer coupling condenser A5 until
output meter reading is a minimum. Final adjustment is to be made with high signal input so that an accurate
adjustment can be made,

H. With signal generator connected to radiating loop and set to 1620 Kc adjust oscillator trimmer A6 on variable con-
denser until output is maximum. Variable condenser is to be fully opened during this adjustment.

I. Set signal generator to 1400 Kc and rotate variable condenser until output is maximum. Adjust R. F. trimmer A7
on variable condenser until output increases to a new maximum, Rotate variable condenser slightly to obtain another
maximum output. Rc~adjust trimmer until output is again a maximum. Repeat this cycle until no further increase
in output can be obtained.

NOTE: When adjusting A7 R. F. Trimmer, make sure the set loop is the same distance from and in the same
position with respect to the chassis and batteries as it would be when the set is mounted in the cabinet with the back

I. The alignment procedure should be repeated in the original order for greatest accuracy. Always kcep the output
from the signal generator at its lowest possible value to make the AVC action of the receiver ineffecctive.

The sensitivity of this set should be approximately 180 uv/meter with 400 cycle 30% modulation and 50 milliwatt

o John F. Rider

Page 2:

PAGE 20-8 NOBLITT-SPARKS

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Rider

Page 3:

NOBLITT- PARKS PAGE 20-9

MODELS 3501>, 3511>, 350-11?

comm n_o I4 on

GNU

? John F. Rider

Page 4:

PAGE 20-10 N0?l_._I_TT-SPARKS

MODELS BSO-UP, 351-UP;

SUBJECT: Circuit and Model Number Changes.

Change covered in this supplement.

l. Circuit change to reduce hum, prevent oscillation and improve reception.

2. Model number changes (BSO-UP and SSl-UP) to comply with Underwriters'
Lab requirements.

The following changes were made in production and can be used as repair measures
on sets of earlier production now in the field.

Hum Reduction.

The 100 mfd. 10 V. section of the Electrolytic Condenser was changed from the

end of the 5V4 filament (Pin #1) to the center tap of the 5V4 filament (Pin #5)
and a .5 mfd, 200 V. Condenser (Part #A22588) was added across the 1850 ohm metal
clad lO watt Resistor, R9. This Resistor is mounted on the front chassis flange.

To make this change in the field, remove the two yellow wires from the lOO mfd.
lOV. lug on the Electrolytic Condenser (0180). Connect these two wires together,
placing the joint so that it can not touch anything. Then connect a piece of
wire_from this condenser lug to #5 pin of the 5V4 socket. Connect .5 mfd. 200

V. Condenser (Part #A22558, chosen for its small size due to space limitations)
to the two lugs on the metal clad resistor.

Oscillation Prevention.

The AVC characteristics were modified to prevent oscillation and improve
reception, by adding a 100,000 ohm, 1/5 watt Resistor, R18 (Part #020271-104)

connected from Pin #l of 1U4 R.F. amplifier to the lug on the variable condenser
mounting screw (AVC).

z Model Number Changes.

A 22 ohm fusing resistor was added in series in the high side of the AC line I
to the Selenium Rectifier, to comply with Underwriters' Lab. requirements.
All sets having this change will be designated as Model SSO-UP or 55l~UP,

Precautions which should be taken to prevent excessive hum and audio feed back.

edge of the chasis flange, as far away from the bottom end of the

I. F. transformer and associated leads as possible.
2. See that the audio coupling condenser connected to center lug on the
F volume control is separated as much as possible from the output trans-
former leads, and the black molded 2 watt, 82 ohm resistor, R10.

5. See that the output transformer leads are not behind the speaker near
the 1U5 tube.

l. See that the AC lead along back chassis flange is dressed along the I

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