Rider BEN CRISSES Operating instructions

REPAIRING
No. 224
by BEN CRISSES and DAVID GNESSIN
a RIDER publication

$2.75
BEN CRISSES
DAVID GNESSIN
REPAIRING PORTABLE AND CLOCK RADIOS
John F. Rider Publisher, Inc., 116 West 14th Street
New York 11, N. Y.
-

Copyright June 1958 by
JOHN F. RIDER PUBLISHER, INC.
All rights reserved. This book or any
parts thereof may not be reproduced
in any form or in any language
without permission of the publisher.
Library of Congress Catalog Card Number 58-12136
Printed in the Uhited States of America

preface •
Because of requirements of mobility, compactness, etc., the de-
sign of portable and clock radios presents special repair problems
to the technicians, many of them different from the usual radio re-
pairs. The authors have emphasized these problems in this book.
No attempt is made or intended to create the impression that port-
able and clock radios are separate and distinct from conventional
ac-dc types. Instead, the authors have assumed that the reader has
a knowledge of basic radio repair and theory, and, for this reason,
have concentrated their information for use in the servicing of port-
able and clock radios.
Theory and other basic information have been kept to a mini-
mum so that practical information be emphasized. The organiza-
tion of this book is such that it enables the user to find all his
required information on a subject in one section, with cross-refer-
encing not required. Finally, the examples given are of equipment
or circuits that enjoy wide popularity. It should be emphasized
that the units discussed are chosen because their high reliability has
made them so very popular, and not because they are unusually
susceptible to breakdown.
y

vi PREFACE
The book begins with an introduction to typical portable radio
circuits. Emphasis is placed on the filament circuitry and how the
major problem of current drain is handled. It then deals with trans-
istor connections and circuits. The portable radio power supply is
examined at length, with observations on battery testing and storage.
Three chapters are devoted to repair, replacement, and align-
ment, including a detailed discussion of probable sites of mechanical
troubles, a full list of all repair equipment needed, notes on new
parts and substitution of old, and step-by-step analysis of replace-
ment procedures and short-cuts. The text also presents an ample
discussion of design improvement - adjustments that go beyond
mere repairing of minor troubles that result in long-term improve-
ment of performance or extension of life of the set.
A final unique chapter is devoted to clock radios. It discusses
the circuitry and switching of these receivers, the varieties of clock
movements and steps in their disassembly and adjustment, clues to
probable defects in clock mechanisms, and tips on cleaning and
lubricating.
The authors wish to extend their appreciation to the following
organizations for making available much of the data and material
required for the book: Admiral Corp.; Crosley Div., Avco Mfg. Co.;
Electronic Industries Association (EIA) ; Electronic Technician;
National Electronic Distributors Association (NEDA); Motorola,
Inc.; RCA Service Co., Inc.; Raytheon Mfg. Co.; Sessions Clock
Co.; Telechron Div. of G.E.; Zenith Radio and Television Corp.
The authors also express their appreciation to Mr. I. Remer,
for his many suggestions; and last but not least to their families, who
showed such wonderful patience and understanding while this book
was being written.
New York, N. Y.
June 1958
Ben Crisses
David Gnessin

contents •
1, introduction to portable and clock radios, 1
2. power supplies, 13
3. mechanical troubles and repairs, 36
4. general troubleshooting, 47
5. repair and replacements, 68
6. alignment, 90
7. design Improvement, 98
8. clock radios, 106
vii

1. introduction to portable and clock radios •
In recent years there has been a steadily increasing demand for
radios that are not only light enough and compact enough to carry
anywhere, but also capable of playing wherever they may be taken.
There has been, at the same time, a growing market for radios that
indicate the time, wake one in the morning, and lull one to sleep at
night. This has resulted in radios that are more complicated, both
electronically and mechanically, than those of former years. They
pose unusual problems to the men who repair and maintain them.
No longer can a service technician look at the underside of a
chassis and make routine repairs. He must trace, or at least examine
more closely, a complex circuit before he takes action.
Manufacturers of portable and clock radios have taken conven-
tional superhet circuits and modified them to satisfy the demands of
the public. For portable radios, the circuits have been changed so
that sets may play on battery only, or on battery, on a-c and on d-c
lines. These sets are commonly referred to as three-way portables.
In addition, I-volt miniature tubes, subminiature tubes, transistors,
printed components, and printed wiring are used more and more

2 REPAIR.ING PORTABLE AND CLOCK RADIOS
as manufacturers strive for smaller, more portable radios. Further-
more, there are three-way portable radios that can operate from
117-volt or 230-volt ac-dc power sources and cover a frequency range
greater than the broadcast band (535-1605 kc).
Clock radios use conventional I17-volt a-c radio circuits, to
which a clock mechanism has been added. The clock includes a
mechanical switch that can turn the radio on or off at preset times.
Clock-portables are also available, in which a conventional electrical
control clock can be plugged into the portable radio when using
house current, and unplugged when the portable is operated on
batteries.
To clarify the portable radio picture, the differences between
ac-dc radios and portable radio receivers will be shown in this chap-
ter and in Chap. 2. These differences lie largely in the filament and
power supply circuits.
TYPICAL TUBE-TYPE PORTABLE RADIO CIRCUITS
The great problem in portables is current drain. A special set
of tubes has been designed to overcome this difficulty.
Table 1-1
lists the tube lineup (in typical sets A, B, C, and D) in the majority
of portables (except transistor types) being manufactured today.
Table 1-1
Stage Set A Set B Set C Set D
R-F or I-F IU4
IAH4 INS
IAH4
Converter IRS
or
IV6 IA7 IV6
IL6
Det-Ampl
IU5
IAJ5
IH5
IAJ5
Output 3V4
none used
or
IAG4
3Q5 (a transistor
3S4 is used)
Rectifier 11723
none used 117Z6
none used
or (battery only) (battery only)
selenium

INTRODUCTION TO PORTABLE AND CLOCK RADIO$ 3
LINE CORD
SHOWN IN
POSITION FOR
BATTERY
OPERATION
VOL CONT
a ON·OFF SW
"B" BATTERY
90V
TOP a BOTTOM
455 KC Ill I F
TOP 6 BOTTOM
455KC2!1>1F
"A' BATTERY
7. 5 V
Fig. 1-1. Typical tube layout of miniature-tube set.
1620 KC
osc.
Fig. 1-2. Typical tube layout of miniature/submlniature-tube set.
CONVERTER
e-------
B A
IF, AF,
DETECTOR
OUTPUT
e+......±l1!1l1----e----'-t+ 111- ________________ ____,
Fig. 1-3. Battery supply circuits; note the filaments In parallel.

4 REPAIRING PORTABLE AND CLOCK RADIOS
Typical tube layouts. Figures 1-1 and 1-2 show the tube layout
and tube-type combinations used in many portable radios. Figure
1-1 shows a typical set using miniature tubes, and Fig. 1-2 a typical
set using subminiature tubes with a miniature power amplifier tube.
D-c filament supplies. For battery economy, tubes used in port-
able radio receivers are of the filament type, and require direct
current for filament operation. Figure 1-3 shows the supply circuits
of a set operating on battery power. The required direct voltages
for B+ and filaments are supplied in parallel because the total
drain is small.
Figure 1-4 shows the filament circuit popular in three-way sets.
This set uses a 9-volt battery for the filament circuits, for portable
DETECTOR
RF
CONVERTER
IF
1.4V
Cl
C3
R4
AUDIO
OUTPUT
POWER
SWITCH
BATTER: CDC
9V =A BATTERY
R6
Fig. 1-4. The filament circuits in a typical three-way portable radio.
operation. Note that the series .connection of filaments places the
audio output stage near the positive end of the d-c source. (The
diagram shows the power switch in BATTERY position.) Placing the
output tube at the positive end of the d-c source provides a means
of securing the required d-c bias voltage for the output stage in the
following manner:
The audio output control grid is returned through R4 to pins
I and 5 of the r-f stage. This point is I .4 volts positive with respect