Zenith Radio Corp. 090 Schematic

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Manufacturer:Zenith Radio Corp.

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Page 1:


Zenith 070,90.V-8

Chassis 2012-4)` is used in Models
090,90 and V-8. This chassis is more
or less similar to Chassis 2012 and
2012-] that was used in Models AH,
CH, and RH, which are shown on
the following pages in Rider':
Manuals: page 1-23 in the revised
edition; i"674,-E, in the early edition,
and page 2717 in the Rider-Combina-
tion Manual. The circuit changes that
were made in Chassis 2012 to make
the Chassis 2012-4] are shown below
and it is suggested that you make a
notation in your Index about the
similarity that exists between these two

The antenna circuit has been revised,
as may be seen by comparing Fig. 1
with the schematic of Chassis 2012 on
one of the pages mentioned above.
Instead of a threegang condenser
denser is used with the fourth section
tuning the antenna winding. (The
part number ofthe four-gang condenser
is 22-134.) The winding in the
antenna circuit, which is tuned by the
fourth section of the new condenser,
has been added to the antenna coil
assembly, Note that the condensers
and resistors in this part of the circuit
_are the same asI those shown in the
schematic for the early chassis.

The padder condenser assembly
(Part Nos. 22-120 and 22-82) has
been replaced with a single variable
condenser, Part No. 22-129. Also the
8-1nf. filter condenser (Part No. 22-
121) mounted at the side of the con-

Fig. I. Antenna circuit oi Zenith Challis
20|1-4J shows new connections.

denser gang has been removed and
mounted below the chassis. No mount-
ing base is used, and it carries a new
part number, 22-136.

Fig. 2 shows the voltage divider,
`the a.v.c. tube, and the new local-dis-
tance switch. Note that the lead
marked "To Local-Distance Switch"

Fig. 2 which carries an arrow in the
plate circuit of the 24. tube. Note also
that the condensers, Part No. 22-99, in
the Chassis 2012 have been eliminated,

and that the One in the plate circuitv

of the 24 tube has been replaced with
one having a value of 0.03 mf., Part
No. 22-111. The value of the resistor
connected between the "Local-Dis-
tance Switch" and the lead to the tone
control (the one at the right of Fig. 2)
has a value of 4.5 megohms, Part N0.
63-188. The 0.1-mf. condenser, con-
nected between the movable arm of the

Fig. Z. A "Local-Distance" switch is new
included in Znnilh Chassis 4012-41.

volume control and ground, has been
eliminated. The part number of this
condenser was 22-1 15.

In other respects the chassis 2012-4]
is the same as chassis 1012.

This power ack, used With Models
39, 69-A, and 40-A, will be found on
the following Pages in Ride/.f Manualr:
1-12 in the fevired edilian; *665 in 1he
early edition, and 2698 in the Rider-
Cnmbinalian. The values of some of
the resistors and condensers Were un-
available at the time of Publication and
are given below; this data was supplied

The total resistance of the voltage
divider is 7,250 ohms, The resistor
designated as Part No. 22-42 is now a
part of the voltage divider and a change
should be made in your diagram, al-
though the resistor is still connected be-
tween the center tap of the 7.5-volt
winding and ground. Starting at the
top of the diagram, the first section of
the divider, i.e. down as far as the blue
lead, is 1000 ohms. The next section,
between the blue and red leads, is 3500
ohms. Between the red lead and
ground, 1000 ohms. The section form-
erly designated as 22-42, is 1750 ohms.

The condenser in the yellow lead to
the left of the choke is 2 mf. The one
to the right of the choke in the green
lead is 4 mf., as is also the one in the
blue lead. The condenser in the red
lead, shunting the 1000-ohm resistor, is

MODELS oso,90,v-s Moores 91 92 '
Chassis 2012-4J ZENITH RADIO CORP' Noi-.es '
MODE.. gil-12 MODELS 811,862,865
Alignment,$00k9`li in Fig. 1 is connected to that lead in Zaniih Bl l, 862. 865| 366, [|62

The model 811 (Chassis 5609) em-
Ploys a 6-inch speaker, Part N0. 49-93;
models 862 and 1162 (Chassis 5610)
use a 12-inch dynamic speaker, Parr No.
49-94. The schematic shown on Zenith
page 6-5 in Ride/r Volume VI is used
in both of these chassis. Below will-be
found a sketch showing the locations- of
the trimmers and the tube sockets.-

Balance i-f, transformers at 252.5 kc.
with signal generator connected to the
grid of the 6A7 and the chassis ground.

Adjust wave-trap padder (located be-
neath the chassis at rear right side) for
weakest signal with 252.5 kc. signal genA
erator connected between antenna and

Turn wave-band switch clockwise to
the highest frequency band and set signal

Top view of 'he Zenith chassis 5609 and 56|0,
showing tubes and trimmers.
generator to 15 mc., still connected to
the antenna and ground. Balance oscilla-
tor trimmer on gang condenser for cor-
rect dial reading at this frequency.

Turn wave-band switch counter-clock-
wise to standard broadcast Position. Ad-
just broadcast oscillator trimmer (lo-
cated beneath the chassis at the right
center) for correct 'dial reading at 1400
kc. and adjust r-f. and lst detector trim-
mers on gang condenser for loudest sig-

Set signal generator at 600 kc. Adjust
oscillator broadcast padder through hole
in top of chassis, simultaneously rocking
the dial back and forth, for loudest

Zenith 9|l 92

The value of the center-tapped re`
sistor, Part No. 63-210, was omitted
from the list of parts shown in Rider's
Manuals on Pages 2-8, 674-N and 271'4.
The section connected to the junction
of the speaker field and the choke is
2,800 ohms and the section connected
to Part No. 63-167 is 10,000 ohms.
Please make this addition to the sche-
matic diagram of this ser in your Volume

(C)John F. Rider, Publisher

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