Service manual

923-03443R1 2 ZLDA1
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. If
any fuse (or Fusible Resistor) in this TV receiver is blown, replace it
only with the factory specified fuse type and rating. When replacing
a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the
resistor 10mm away from PCB. Always keep wires away from high
voltage or high temperature parts.
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. Service work should be performed
only after you are thoroughly familiar with these safety checks and
servicing guidelines.
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.
GENERAL GUIDANCE
An lsolation Transformer should always be used during the servicing
of a receiver whose chassis is not isolated from the AC power line. Use
a transformer of adequate power rating to protect against personal
injury from electrical shocks. It will also protect the receiver and it’s
components from being damaged by accidental shorts of the circuitry
that may be inadvertently introduced during the service operation.
Before returning the receiver to the customer, always perform an AC
leakage current check on the exposed metallic parts of the cabinet,
such as antennas, terminals, etc., to be sure the set is safe to operate
without damage of electrical shock.
LEAKAGE CURRENT COLD CHECK (ANTENNA COLD CHECK)
With the instrument AC plug removed from AC source, connect an
electrical jumper across the two AC plug prongs. Place the AC switch
in the on position, connect one lead of ohm-meter to the AC plug
prongs tied together and touch other ohm-meter lead in turn to
each exposed metallic parts such as antenna terminals, phone jacks,
etc. If the exposed metallic part has a return path to the chassis, the
measured resistance should be between 1M½ and 5.2M½. When the
exposed metal has no return path to the chassis the reading must be
infinite. Any other abnormality that exists must be corrected before
the receiver is returned to the customer.
LEAKAGE CURRENT HOT CHECK (SEE BELOW FIGURE)
Plug the AC cord directly into the AC outlet. Do not use a line
Isolation Transformer during this check. Connect 1.5K/10watt resistor
in parallel with a 0.15uF capacitor between a good earth ground
(Water Pipe, Conduit, etc.) and the exposed metallic parts. Measure
the AC voltage across the resistor using AC voltmeter with 1000
ohms/volt or more sensitivity. Reverse plug the AC cord into the AC
outlet and repeat AC voltage measurements for each exposed metallic
part. Any voltage measured must not exceed 0.75 volt RMS at 0.5mA.
In case any measurement is out of the limits specified, there is the
possibility of shock hazard and the set must be checked and repaired
before it is returned to the customer.
LEAKAGE CURRENT HOT CHECK CIRCUIT
A
.C. Voltmeter
1500 OHM
1
0
WATT
Place this probe
on each expose
d
metal part.
Good Earth Ground
such as the Water
Pipe, Conduit, etc.
0.15uF
REGULATORY INFORMATION
This equipment, trade name Zenith, model number, IQD27D53T, has
been tested and found to comply with the limits for a Class B digital
device, pursuant to Part 15 of the FCC Rules. These limits are designed
to provide reasonable protection against harmful interference when
the equipment is operated in a residential installation. This equipment
generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instruction manual, may
cause harmful interference to radio communications. However, there
is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning
the equipment off and on, the user is encouraged to try to correct
the interference by one or more of the following measures: Reorient
or relocate the receiving antenna; Increase the separation between
the equipment and receiver; Connect the equipment into an outlet
on a circuit different from that to which the receiver is connected;
Consult the dealer or an experienced radio/TV technician for help.
The responsible party for this device compliance is:
Zenith Electronics Corporation
201 James Record Road
Huntsville, AL 35824, USA
Digital TV Hotline:
1-800-243-0000
Dolby Digital® Manufactured under license from Dolby Laboratories.
“Dolby” and the double-D symbol are trademarks of Dolby
Laboratories. Confidential Unpublished Works.
©1992-1997 Dolby Laboratories, Inc. All rights reserved.
The presence of the DTV certification mark indicates that this product
will successfully receive digital television transmissions that conform
to any and all of the video formats described in the ATSC Digital
Television Standard.
VCR Plus+, PlusCode and GUIDE Plus+ are trademarks of Gemstar
Development Corporation. The VCR Plus+ and GUIDE Plus+ systems
are manufactured under license from Gemstar Development
Corporation and VCR Index Systems B.V., respectively.
Gemstar is not in any way liable for the accuracy of the program
schedule information provided by the GUIDE Plus+ system. In no
event shall Gemstar be liable for any amounts representing loss of
profits, loss of business, or indirect, special, or consequential damages
in connection with the provision or use of any information,
equipment, or services relating to the GUIDE plus+ system.
PRODUCT SAFETY SERVICING GUIDELINES FOR AUDIO-VIDEO PRODUCTS