Noblitt-Sparks Industries, Inc. 357T Schematic

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Product Information:
Model:357T
Manufacturer:Noblitt-Sparks Industries, Inc. (Arvin)
Description:RE-273

Schematics Content:

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Page 1:

NOBLITT-SPARKS PAGE 20-11

MODELS 356T, 357T;

SPECIFICATIONS

FREQUENCY RANGE

LOUD SPEAKER

Type: Permanent magnet
Size: 4 Inch
Voice coil impedance ____________________ 3.2 Ohms

CHASSIS FEATURES

Automatic Volume Control
Built-in Loop

POWER SUPPLY OPERATING CONTROLS
105425 Volts, AC-DC, 35 Watts 1, Left knob ___

POWER OUTPUT 2. Right knob __
PHYSICAL DIMENSIO

Plate load _ __ 2000 Ohms Leogih _ 8% inches
Height _ 6 inches
Depth __ __ 53/4 inches

Models 356T Gt 357T are identical except for Color, 356T is Sandalwood, 3571' is Willow Green. l

POSITION OF POWER CORD PLUG
On AC, the power cord plug should be tried in both its possible positions in the receptacle, and left in the position that
gives least hum. On DC, the receiver will work in only one position of the plug in its receptacle.

THE ANTENNA

This receiver has a built-in loop which gives satisfactory reception in most locations. If the receiver is located some
distance from a broadcasting station, or where the electrical interference is high, an outside antenna connected to the
pickup lead on the loop, will improve reception.

This receiver is designed to operate without a ground connection and no attempt should be made to use one.
ALIGNMENT PROCEDURE

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

B. Connect signal generator high side through .05 uf or larger condenser to IZSA7 grid. Connect low side of signal gener-
ator to Chassis. Connect output meter across speaker voice coil.

C. Open variable condenser?

D. With signal generator set at 455 Kc, increase output of generator until output is heard in speaker. Adjust IF trimmers I
A1, A2 or A3 until maximum output meter 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 ratio.

E. With signal generator connected to a radiating loop and set to 1620 Kc, adjust oscillator trimmer A4 on variable con~
denser until output is maximum. Variable Condenser is to be fully opened during this adjustment.

F. Set signal generator to 1400 Kc and rotate variable condenser until output is maximum. Adjust R. F. trimmer A5 on I
variable, condenser until output increases to a new maximum. Rotate variable condenser slightly to obtain another
maximum output. Re-adjust trimmers until output is again a maximum, Repeat this cycle until no further increase in
output can be obtained. Final adjustment to be made with the signal generator output at lowest level consistent with |
good signal to noise ratio.

G. Set signal generator to 1000 Kc and tune radio to maximum output. Adjust variable condenser plates for maximum

H. Set signal generator to 600 Kc and proceed as in G above.

Set signal generator to 540 Kc and make sure that radio will tune to maximum output slightly before variable condenser
is fully closed.

I. Recheck alignment and calibration at 1400, 1000, and 600 Kc, making any necessary readjustments.
K. Tune the variable condenser through its entire range to make sure it is not shorted at any point. i

(C)John F. Rider

Page 2:

PAGE 20-12 NQBLITT-SPARKS
MODELS 356T, 357m

ANTENNA LOOP

SPEAKER "B coN. 5 E
? TUBE LAYOUT _

lOCATION OF PARTS UNDER CHASSIS

(C)John F. Rider

Page 3:

NOBLITT-SPARKS PAGE 20-13

MODELS ,35613 357T

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(C)John F. Rider

Page 4:

PAGE 20.14 NoBuTT-sPARKL

MODELS 360mm, 361TFM;

SPECIFICATIONS

FREQUENCY RANGE
Broadcast (AM) __ ___ 540-1600 kc

FM Converter
FM-AM DET IST Audio AVC

____ Output

Undistortcd __ _ 2.5 Watts
Maximum __ __ 3 Watts
Platc load _ _ 2000 Ohms

LOUD SPEAKER
Type: Permanent magnetv 1.47 o7.. Alnico 5
Size: 5 Inch
Voice coil imjwdancc ____________________ 3.2 Ohms
CHASSIS FEATURES
Automatic Columc (lotrol
Built-in Loop
Underwriters Listed
Bass Boost (.ircnit
OPERATING CON-[11015
1. cht knob __
2. Right knob _
3, Center knob
PHYSICAL DIMEIN IONS
Length __________________________ 12 11/16 inches
Height _ __ 7 1/8 inches
Depth ___ _ 7 11/16 inches

_ ON-OFF Sw and Voluim`
___ Tuning
___ Band Sw

Models SSOTFM is in a walnut cabinet. Moch 861TFM is in a Willow Green cabinet. The Chass is the same in both

ALIGNMENT PROCEDURE

l. Plug set into 117 V. power source, turn volume control
full on and band switch to AM, (left).

2. Connect output meter across speaker voice coil.

:3. Connect signal generator high side through .05 mfd.
condenser to converter grid and generator ground lead
to receiver floating ground. Open tuning condenser.
ator to test loop. Set signal generator io 1850 Kc.
Tune trimmer A5 on oscillator section of tuning wn~
denser :for maximum output.

4. Close tuning condenser and set pointer at end mark of
dial. Open tuning condenser. Connect signal gener-
ator to 1650 Kc. Tune trimmer A5 on oscillator section
of tuning condenser for maximum output.

5. Sct signal generator to 1400 Kc. Adjust timing shaft
until maximum output is obtained. Tune antenna
trimmer A6 on tuning condenser for greatest output.
Reset tuning shaft until output is again a maximum.
Retune antenna trimmer. Repeat this cycle of opera-
tions at 1400 Kc until no further increase of ou ut
can be obmined. Keep enerator out-put at a ow
value to prevent detuning y A. V. C. action.

6. Set signal generator to 600 Kc. Adjust tuning shaft
for maximum output. Adjust tuning condenser plates
for maximum output.

7. Check sensitivity at 1000 Kc. If sensitivity is too low,
tuning condenser lates can be adjusted for tracking at
this frequency. I? this adjustment is made, tracking at
600 Kc must be readjusted.

8. Check coverage and calibration after alignment.
Covera e should include 535 and 1650 Kc. Calibration
should e such that pointer covers some part of calibra-
tion mark. If coverage and/or calibration are not
correct, plates of tuning condenser can be adjusted,
Calibration check points are 1400 100() 600 and 540
Kc. If oscillator plates are adjusted, tracking of
antenna section must be rechecked and corrected if

9. Check setting of trimmers on tuning condenser. Trim-
mer adjustments must not be extremely tight nor so
loose as to be noisy or vibrate.

10. After alignment, check for noise due to condenser plates
touching or pointer touching dial as tuning shaft is
turned through the ful] tuning range.

11. The sensitivity of this set should be approximately 500
uv/m with 400 cycles, 30% modulation and 200 milli-
watts, (.8 volt output.

. Turn band switch to FM, (right).
. Connect (FM) 1.F. generator to the second 12BA6 LF.
amp. grid, (lug #1) through the .01 uf mica dummy.

tow

Connect os 'lloscope across volume control. With
150 Kc deviation 10.7 on the I. F. generator and
tbe same audio voltagc used as horizontal sweep
on the scope, adjust thc ratio detector transformer slugs
A7-A8 for the characteristic "S" curve (See Fig, 1),
with maximum vertical height on the scope. After
this adjustment the top slug of the ratio detector should
not be moved during thc rest of thc alignment.

3. Connect I.F. generator to mixer grid through .01 mica
dummy. Using 23 Kc deviation 10.7 Mc adjust
10.7 Mc I. transformer slugs A9, A10, A11 and
A12 for maximum output. Maximum output may be
indicated by maximum vertical height on the scope or
maximum voltage on a standardoutput meter across
the voice coil of the receiver. After tbe two LF. trans-
formers have been aligned the bottom slug A8 of 'the
ratio detector should also be peaked.

The characteristic "5" curve of the complete I.F.
channel should be checked by applying a 10.7 Mc
signal with 150 Kc deviation to the mixer grid and
obscrving the curve on the scoke. It should
not be vcry much different from that observed in step 2.

4. Connect R.F. (FM) generator (88 to 108 Mc) to the

antenna terminals through the standard 800 ohm
dummy (150 ohm in each side of generator leads). Use
R.F.gcncrator with 23 Kc deviation, With the variable
condenser Lompletcly open and S.G. tuned to 108.5 Mc
adjust oscillator trimmer A13 small ceramic trimmer)
for maximum reading on output meter.
Then tune reccivcr to low end of band (variable com-
pletely closed) and S.G. to 87.5 Mc. If the receiver
docs not tum.l to this frequency the FM oscillator coil
L4 will either have to be squeezed together or length-
ened to cover thc band, (squeezing lowers and lengthen-
ing raiscs the frequency). Any change in the coil will
have to be compensated by the trimmer at the high end
of the band.

5. WVith the same S.G. connections as per paragraph 4

tune S.G. and set to 105 Mc. Tune R.F. trimmer A14
for maximum output at the same time rock variable
back and forth throu h the frequency. (Rocking is
necessary because slig t oscillator pulling causes cr-
roneous maximum readings).
Tune S.G. and set the 90 Mc, Adjust R.F. coil L3
length for maximum output hy squeezing or lengthen~
ing. Any change in the coil will have io be compen-
sated at 105 Mc by the R.F. trinruncr A14,

6. After steps 4 and 5 are finished check calibration and
band covcrage. Steps 4 and 5 may have to be repeated
if set is off calibration. Band coverage should be 87.5
Mc to 108.5 Mc. Sensitivity should be approximately
200 uv a! 105 Mc, 98 Mc and 90 Mc.

(C)John F. Rider

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