Arvin 618 Schematic

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Manufacturer:Arvin (Noblitt-Sparks)

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Page 1:

Arvin 518, MBA, etc.

ln order to eliminate the hum in the
chassis used in these and other six-tube
models, follow this procedure:

Remove the chassis from the cab-
inet. Locate the ground lug on the
6Q7G tube socket (see chassis layout
on page 8-16 of Rider': Volume VIII).
This lug is fastened to the chassis by
a rivet which attaches the 6Q7G
socket to the chassis. Bend this lug
over and solder it to the chassis and
then recheck for hum. If this is sol-
dered correctly, the hum level should
be brought to a minimum.

Pilot XII4. X1I5

Changes have been made in the chas-
sis used in these models, which have a
similar schematic to the one shown on
page 6-15 in Rider".\l Volume VI. The
condenser; 032 and C33 in the plate
circuit of the second detector have been
removed from the circuit, so that now
the switch 53 is used to short out only
the one condenser, C34, which now
has a value of 250 mmf.

The value of the 10,000-ohm re~
sistor No. 26 has Vbeen changed to 4
6,000 ohms. _This is in the primary
circuit of the pushpull input trans-

A line condenser (lOOO-volt, paper)
has been added across the primary of
the power transformer. This is a dual
condenser, grounded between the 0.01-

Automatic 960A

The accompanying partial schematic
shows a change which was incorporated
in the 960 series, the schematic of
which is shown on page 9-2 in Rider'r
Volume IX. Note also that the re-
ceivers in which this change has been
made have an i-f peak of 480 kc, in-
stead of 1-56 koand that they are iden-
tified by the letter "A" after the model

New .umm eireuu of eh. Automate

Arvin BIB. m, ode.

ln order to reduce the hum level of
the models in which the 8-tube chassis
is Wed, follow this procedure:

Remove the chassis from the cab-
inet. ` Unsolder the 250,000-ohm plate
resistor of the 6F5G tube from the
B+ terminal, which is the lug on the
l6-mf-300 volt electrolytic con-
denser. See chassis layout on page
8-20 of Rider'r Volume VIII. Con-
nect this resistor to the first tap down
from B+ on the voltage divider te-
sistor R87. This voltage tap supplies
the potential for the 6A8G anode grid.
Recheck for hum, which now should
be reduced to a satisfactory level,

Oldsmobile 982043

ln some of the early receivers (un-
der_ serial A-20,000) of this model, sev-
eral dif'ferences exist which should be
noted on page 9-1 in Rider's Volume

Resistor No. 46 is 100,000-ohms in-
stead of 20,000.

Resistor No. 54 is 125,000 instead of
100,000-ohms and No. 55 is 75,000 in-
stead of 100,000-ohms.

Resistor No. 44 and condenser No.
26 have been transposed, i.e. the re-
sistor is connected to the grounded end
of resistor No. 53 instead of the con-

The value ofV condenser No. 82 is
indicated as 0.000063-mf and its con-
nections are as follows: one terminal is
connected to the junction of condenser
No. 26 and the tap from resistor No.
58 and the other termnial is connected
to the junction of condenser No. 18 and
the left end of resistor No. 58.

Emerson Chassis AF

Receivers using this chassis and bear-
ing serial numbers above 1,244,716
differ from the schematic shown on
page 8-'45 in Rider'r Volume VIII.
The condenser C-17 is omitted and
the negative side of the filament cir-
cuit is grounded to the chassis.

Refer to the schematic shown on
page 8-9 of Rider-'r Volume VIII. Dur-
ing production, the 47,000-ohm resistor
(8) and the filter condenser (7) were
removed an'd the r-f secondary was
grounded directly, thus removing AVC
from the 6L7G mixer tube. The bot-
tom of the antenna coil semndary was
then connected directly to the 1-meg-
ohm resistor (9), A 1000-ohm variable
resistor was added in the cathode cir-
cuit of the 6J7G AFC control tube
(at 37) to make possible compensa-
tion for variation in calibration due to
variation in tube characteristics. This
control was found unnecessary and was
removed in later runs.


Refer to schematic shown on page
8-7 of Rider'r Volume VIII. During
production, the 47,000-ohm resistor
(16) and the 0.05-mf condenser (7)>
were removed and the r-f secondary
was grounded directly, thus removing 1
AVC from the 6L7G mixer tube. The
bottom of the antenna coil secondary
was then connected directly to the 470,-
000-ohrn resistor (17).

This model is identical to model G-
55, except for the cabinet and the loud
speaker, which has a part number RS-
095. The 12-inch cone of this unit
has a part number RC-943.

The servicing data for model G-55,
found on page: 9-3, 9-4, and 9-5 of
Rider's Volume IX, apply to the G-57.
This additional model number should
be added to the listing in your Index.

Shomberg-Carlson Push-Button Tuners

The push buttons on all the new
receivers, such as those whose servicing
data are found in Rider'r Volume IX i
which employ padding condensers for F
tuning purposes are set up from the`
front of the chassis. It is unnecessary
to get into the back of the receiver to
set up the desired stations, except to
adjust the electric tuning switch on l
the rear of the chassis.

To set up the stations, it is only
necessary to remove the escutcheon over
the push buttons and the adjusting
screws become readily accessible. These
escutcheons are held in place by sev-
eral Phillips type screws, which can
be removed with any small pointed in-
strument, such as a small naillile or an
old knife blade. However, the use of
a special tool is recommended, as this
will not mar the surface of the screw

Dewalt! Hoe ?

This model is identical with the
Models 1104 and 1105, shown on
page: 9-1 and 9-10 of Rider's Volume
IX, except that the new model has an
additional' short-wave band for the 14-
40 mc range, giving it a total of five

RCA sMa, aMi '
On 8M3 and 8M4 receivers, it is

often advantageous to connect the 22-
mmf condenser (C1, on page 9-37 of
Rider's Volume IX) from the output
end of coil L1 to ground, instead of
from the antenna end. Later runs of
sets include this change. Note also
that good electrical contact is required
between vibrator-transformer and chas-
sis to minimize internal noise.

(C)John F. Rider, Publisher

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