American Bosch 239 Schematic

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Manufacturer:American Bosch (United American Bosch & Fred M. Link)

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Page 1:

The chassis wiring diagram of this
model, which appears on page 3-15 of
Rider): revised Volume II; page dll-K
of the early edition; and page 2401 of
the Rider-Combination Manual, is not
clear in one or two places. So that no `
doubt will be in your mind when check-
ing over two of the condenser banks,


Condenser banks ol Srromborg Model 19

we are showing herewith enlarged
drawings oi the bank having eleven
condensers, in the upper right-hand
side of the diagram, and the nine-con-
denser bank that is shown in about the
middle of the page. You can identify
their positions on the wiring diagram
by the apparatus in the vicinity and by
the color and position of the leads.
Notice that the top ot the sketch shown
here goes to the right-hand side of the
diagram in your Manual.

Philco Model |44

Effective April 15, 1955 the center
tap is removed from the filament wind-
ing on. the power transformer. If a
hum is experienced in reception, conv
nect a 20-ohm, wire-wound resistor
across the filament winding, with center
tap oi resistor grounded. This set is
shown on page 5-41 in Rider's Manual
Volume V.

"X" Models ln The Sporion Line
Some of the Sparton model numbers
conclude with the letter "X". The fol-
V lowing data will no doubt be of value
when seeking equivalent circuits in
Rider's Manuals. In some instances,
the "X" denotes a receiver intended for
export sale and containing a special
power transformer. In other cases, the

letter denotes some addition to
the basic circuit.
Model 27-X is the model 18 chassis
used in a model 27 cabinet. (Rider

(C)John F. Rider, Publisher

Manuals Sparton page 3-10, 3-11,

Model 67-X is the same as the model
67 with a special power trans-
former and is intended for export.
(Rider Manual Spartan 5-10, 5-11,

Model 75-BX is an export model.

Model 80-X is the same as the model
80, with a special power trans-
former and is intended for export.
(Rider Manual Sparton 5-15, 5-16,

Model 81-X is the same as the model
81, with the addition of a wave
trap. (Rider Manual Sparton

Model 8Z-X is the same as model 82,
with the addition of a wave trap.
(Rider ManuaiSparton page 4.-17.)

The i-f. peak of these models, the
schematic of which appears on page
4-10 a] Rider's Volume IV, is 175 kc.
Please make a notation of this on the

Bosch 23?

Please make a note that Model 23|)
is similar electrically to the Bosch
models 236 and 237, the servicing
data on which are found on page 3-11
in Rifle/.r Volume Ill and on page
2531 in the Rider-Combination Mun-
ual. This Model 239 was used in a
table installation and the only diiier-
ence between it and the other models
mentioned is that the antenna and
ground leads were braided together
with the power supply cord in Model


Howard Grand

Please make a notation that the
power unit shown on Howard page
6-16 of Rider'r Volume Vl i5 for
Series 2 of this model, as well as
Series I.

Packard Bell 34

Ii this set should need to be read-
justed, the procedure is as follows: Set
dial to about 1700 kc. and Connect the
output of a signal generator, set at the
same frequency, to the antenna. Adjust l
thc trimmer condensers of the r-f. and
detector stages for maximum output.
All adjustments at looo kc. and ooo
kc. are made by bending the outside
rotor plates of the variable condenser
tuning the r-f. stage. The schematic
diagram of this receiver will be found
on page 6-4 of Rider's Volume VI.

Crosley BIS

We have received word .from the
manufacturer that no servicing data
has ever been issued for the 815, but
ii you get one in the shop look up
Model 8B3, on page 6-10 in Volume
VI of Rider's Manuals. We are ad-
vised that the 8133 is practically the
same as the 815.

Atwater Kent |45I 325

The schematic diagram shown on
page 5-7 11/ Rider'r Volume V is for
the early model but the note at the
bottom of the diagram covers the
changes that were made in the late
model. The elimination of the con-
denser, C4, in the frequency-changing
switch in the late models necessitated a
rearrangement of the parts. The |
chassis layout for the late model is
shown in the accompanying illustration.

The bottom view of 'he chassis used in A-K. Models |45 and 325 of 'he lah typo

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