Zenith 1 COVER Diagram

SERVICE MANUAL

Product Type: Color Television Receiver
Chassis: GA
Manual Series: CM-150
Manual Part #: 923-03349R1
Model Line: A-Line
Product Year: 1998

REVISED EDITION

This revised edition includes the original GA manual
(923-03349) and the first addendum (923-03412).

CONTENTS

General Information/Remote Controls............... 1

Installer’s Menu............................................. 2

Servicing/Troubleshooting ............................. 3

Model/Module Parts Lists ............................... 4

Exploded Views ............................................. 5

Schematics ................................................... 6

Model Series:

A19A02D A25A23W84 LGA20A05DM84
A19A02D4 A25A23W9 LGA20A11DM
A19A02D7 A25A74R LGA20A11DM7
A19A02D74 A25A74R7 LGA20A11DM74
A19A02D8 A25A74R8 LGA20A11DM8
A19A02D84 A25A76R LGA20A11DM84
A19A11D A25A76R7 LGA21A22DM
A19A11D4 A25A76R8 LGA21A22DM4
A19A11D7 A27A11D LGA21A22DM8
A19A11D74 A27A11D4 LGA21A22DM84
A19A11D8 A27A11D8 LGA26A02DM
A19A11D84 A27A11D84 LGA26A02DM4
A20A22D A27A12D LGA26A02DM64
A20A22D4 A27A12D4 LGA26A02DM7
A20A22D8 A27A12D8 LGA26A02DM74
A20A22D84 A27A22BT LGA26A02DM8
A25A02D A27A22BT4 LGA26A02GM
A25A02D4 A27A22BT8 LGA26A02GM7
A25A02D64 A27A22BT84 LGA26A02GM8
A25A02D7 A27A23W LGA26A11DM
A25A02D74 A27A23W4 LGA26A11DM4
A25A02D8 A27A23W8 LGA26A11DM64
A25A02D84 A27A23W84 LGA26A11DM7
A25A11D A27A74R LGA26A11DM74
A25A11D4 A27A74R8 LGA26A11DM8
A25A11D64 A27A76R LGA26A12DM
A25A11D7 A27A76R8 LGA26A23WM
A25A11D74 EKA2667BT LGA26A23WM6
A25A11D8 EKA2968BT LGA26A23WM7
A25A11D84 LGA20A02DM LGA26A23WM74
A25A12D LGA20A02DM4 LGA26A23WM8
A25A12D4 LGA20A02DM7 LGA26A23WM9
A25A22BT LGA20A02DM74 LGA29A11DM
A25A22BT4 LGA20A02DM8 LGA29A11DM4
A25A22BT64 LGA20A02DM84 LGA29A11DM8
A25A22BT7 LGA20A02GM LGA29A11DM84
A25A22BT74 LGA20A02GM8 LGA29A11GM
A25A22BT8 LGA20A04DM LGA29A12DM
A25A22BT84 LGA20A04DM7 LGA29A12DM4
A25A23W LGA20A04DM74 LGA29A12DM84
A25A23W4 LGA20A04DM8 LGA29A23WM
A25A23W6 LGA20A04DM84 LGA29A23WM4
A25A23W64 LGA20A05DM LGA29A23WM8
A25A23W7 LGA20A05DM7 LGA29A23WM84
A25A23W74 LGA20A05DM74
A25A23W8 LGA20A05DM8

Printed in U.S.A.
ZEN REV2 600

Published by Technical Publications

Zenith Electronics Corporation

201 James Record Road - Huntsville, Alabama 35824-1513

ÓCopyright February 1999 by Zenith Electronics Corporation

Revised Edition August 1999

PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS

IMPORTANT SAFETY NOTICE

This manual was prepared for use only by properly trained audio-visual service
technicians.

When servicing this product, under no circumstances should the original
design be modified or altered without permission from Zenith Electronics
Corporation. All components should be replaced only with types identical to
those in the original circuit and their physical location, wiring and lead dress
must conform to original layout upon completion of repairs.

Special components are also used to prevent x-radiation, shock and fire hazard.
These components are indicated by the letter “x” included in their component
designators and are required to maintain safe performance. No deviations are
allowed without prior approval by Zenith Electronics Corporation.

Circuit diagrams may occasionally differ from the actual circuit used. This way,
implementation of the latest safety and performance improvement changes into
the set is not delayed until the new service literature is printed.

Caution: Do not attempt to modify this product in any way. Never perform
customized installations without manufacturer’s approval. Unauthorized
modifications will not only void the warranty, but may lead to property damage
or user injury.

Service work should be performed only after you are thoroughly familiar with
these safety checks and servicing guidelines.

Graphic symbols

The exclamation point within an equilateral triangle is intended
to alert the service personnel to important safety information in
the service literature.

The lightning flash with arrowhead symbol within an equilateral
triangle is intended to alert the service personnel to the presence
of noninsulated “dangerous voltage” that may be of sufficient
magnitude to constitute a risk of electric shock.

The pictorial representation of a fuse and its rating within an
equilateral triangle is intended to convey to the service personnel
the following fuse replacement caution notice:
CAUTION: FOR CONTINUED PROTECTION AGAINST RISK OF FIRE,
REPLACE ALL FUSES WITH THE SAME TYPE AND RATING AS MARKED
NEAR EACH FUSE.

SERVICE INFORMATION

While servicing, use an isolation transformer for protection from AC line shock.
After the original service problem has been corrected, make a check of the
following:

FIRE AND SHOCK HAZARD

1. Be sure that all components are positioned to avoid a possibility of
adjacent component shorts. This is especially important on items trans­ported to and from the repair shop.

2. Verify that all protective devices such as insulators, barriers, covers,
shields, strain reliefs, power supply cords, and other hardware have been
reinstalled per the original design. Be sure that the safety purpose of the
polarized line plug has not been defeated.

3. Soldering must be inspected to discover possible cold solder joints, solder
splashes, or sharp solder points. Be certain to remove all loose foreign
particles.

4. Check for physical evidence of damage or deterioration to parts and compo­nents, for frayed leads or damaged insulation (including the AC cord), and
replace if necessary.

5. No lead or component should touch a receiving tube or a resistor rated at
1 watt or more. Lead tension around protruding metal surfaces must be
avoided.

6. After re-assembly of the set, always perform an AC leakage test on all exposed
metallic parts of the cabinet (the channel selector knobs, antenna terminals,
handle and screws) to be sure that set is safe to operate without danger of
electrical shock. DO NOT USE A LINE ISOLATION TRANSFORMER DURING THIS
TEST. Use an AC voltmeter having 5000 ohms per volt or more sensitivity in
the following manner: Connect a 1500 ohm, 10 watt resistor, paralleled by
a .15 mfd 150V AC type capacitor between a known good earth ground
water pipe, conduit, etc.) and the exposed metallic parts, one at a time.
Measure the AC voltage across the combination of 1500 ohm resistor and
.15 mfd capacitor. Reverse the AC plug by using a non-polarized adaptor
and repeat AC voltage measurements for each exposed metallic part. Voltage
measured must not exceed 0.75 volts RMS. This corresponds to 0.5 milliamp
AC. Any value exceeding this limit constitutes a potential shock hazard and
must be corrected immediately.

A.C. Voltmeter

Good Earth Ground
such as the Water
Pipe, Conduit, etc.

0.15uF

1500 OHM

10 WATT

Place this probe
on each exposed
metal part.

X-RADIATION

1. Be sure procedures and instructions to all service personnel cover the
subject of x-radiation. The only potential source of x-rays in current TV
receivers is the picture tube. However, this tube does not emit x-rays when
the HV is at the factory-specified level. The proper value is given in the
applicable schematic. Operation at higher voltages may cause a failure of
the picture tube or high-voltage supply and, under certain circumstances
may produce radiation in excess of desirable levels.

2. Only factory-specified CRT anode connectors must be used.

3. It is essential that the service personnel have available an accurate and
reliable high-voltage meter.

4. When the high-voltage circuitry is operating properly, there is no possibility
of an x-radiation problem. Every time a color chassis is serviced, the
brightness should be run up and down while monitoring the high voltage
with a meter, to be certain that the high voltage does not exceed the
specified value and that it is regulating correctly.

5. When troubleshooting and making test measurements in a product with a
problem of excessively high voltage, avoid being unnecessarily close to
the picture tube and the high voltage power supply. Do not operate the
product longer than necessary to locate the cause of excessive voltage.

6. Refer to HV, B+, and shutdown adjustment procedures described in the
appropriate schematics and diagrams (where used).

IMPLOSION

1. All direct view picture tubes are equipped with an integral implosion
protection system; take care to avoid damage during installation.

2. Use only the recommended factory replacement tubes.

TIPS ON PROPER INSTALLATION

1. Never install any receiver in a closed-in recess, cubbyhole, or closely
fitting shelf space over, or close to, a heat duct, or in the path of heated
air flow.

2. Avoid conditions of high humidity such as: outdoor patio installations
where dew is a factor, near steam radiators where steam leakage is a factor,
etc.

3. Avoid placement where draperies may obstruct venting. The customer
should also avoid the use of decorative scarves or other coverings that
might obstruct ventilation.

4. Wall- and shelf-mounted installations using a commercial mounting kit
must follow the factory-approved mounting instructions. A product mounted
to a shelf or platform must retain its original feet (or the equivalent
thickness in spacers) to provide adequate air flow across the bottom. Bolts
or screws used for fasteners must not touch any parts or wiring. Perform
leakage tests on customized installations.

5. Caution customers against mounting a product on a sloping shelf or in a
tilted position, unless the receiver is properly secured.

6. A product on a roll-about cart should be stable in its mounting to the cart.
Caution the customer on the hazards of trying to roll a cart with small
casters across thresholds or deep pile carpets.

7. Caution customers against using a cart or stand that has not been listed
by Underwriters Laboratories, Inc. for use with its specific model of
television receiver or generically approved for use with TVs of the same or
larger screen size.

8. Caution customers against using extension cords. Explain that a forest of
extensions, sprouting from a single outlet, can lead to disastrous
consequences to home and family.

CM150 GA - SAFETY

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