28LF-94H (serv.man2) - Sharp TV Service Manual (repair manual)

28lf-94h (serv.man2) service manual
Model
28LF-94H (serv.man2)
Pages
20
Size
856.14 KB
Type
PDF
Document
Service Manual
Brand
Device
TV / CTR
File
28lf-94h-sm2.pdf
Date

Read Sharp 28LF-94H (serv.man2) Service Manual online

1
28LF-94H
SERVICE MANUAL
   AK- 53
 CHASSIS
In the interests of user safety (required by safety
regulations in some countries) the set should be re-
stored to its original condition and only parts identi-
cal to those specified should be used.
CONTENTS
ELECTRICAL SPECIFICATIONS ........................................................................................ 3
IMPORTANT SERVICING NOTES ...................................................................................... 4
CONTROLS & TERMINALS ................................................................................................ 5
PRINTED WIRING BOARD LAYOUT ................................................................................. 7
PARTS LISTING ................................................................................................................... 9
HOW TO UPDATE THE TECHNICAL INFORMATION ...................................................... 19
SHARP  CORPORATION
SE
0028
LF94H00
               Issued: 29
th
 July 2004
In  order  to   service the model 28LF-94H ,  refer  to
the AK-53 Chassis Service Manual
(SE
00
AK53CHA00).
       MODEL
 28LF-94H
 PAL I
  
SYSTEM COLOUR TELEVISION
2
28LF-94H
Use this page to keep any special servicing information as Technical Report (Bulletin), Technical Information, etc.
If only part  number changes are required, just change part number directly the part number in the Parts Listing Section.
If you need more information, please refer to the Technical Report (Bulletin).
SERVICE MANUAL UPDATE LOG SHEET
Part No.
Technical Report  No.
Technical Bulletin No.
Cause / Solution
Page No.
Application
Data /Serial No.
3
28LF-94H
ELECTRICAL SPECIFICATIONS
                                            WARNING
The chassis in this receiver is partially hot. Use an isolation transformer between the line cord plug
and power receptacle, when servicing this chassis.
To prevent electric shock, do not remove cover. No user-serviceable parts inside. Refer servicing to
qualified service personnel.
Specifications are subject to change without prior notice.
•Power Input .................... 220V-240 Volts AC 50 Hz
•Power Consumption
Normal Operation (Method IEC60107) ............ 113 W
Stand-by Operation .......................................... < 3 W
•Audio Power Output Rating (MPO) / Impedance
Internal Left Speaker ................................. 10 W, 7 
Internal Right Speaker ............................... 10 W, 7 
•Speakers
Full range (2 pcs) ................................... 60 x  120 mm
•Picture Intermediate frequency ......... 38.9MHz
•Sound  Carrier Trap ........................... 32.9MHz
•Adjacent Sound Carrier Trap ............. 40.9MHz
•Adjacent  Picture  Carrier Trap ........... 30.9MHz
•Aerial Input Impedance
VHF/UHF ................. 75 ohm Unbalanced
•Tuning Ranges ..... 45.75MHz thru 855.25 MHz
VHF: IR A - J / CC01-CC68 (Hiperband)
UHF: I21 - I69 CH
•White Level
Apply the rated voltage at the rated frequency to the TV set, while it is receiving full white pattern RF signal of 60
dB/µV from its RF input via the pattern generator.
Turn all picture controls to maximum value. Measure the colour temperatures at the center of the screen by
using the colour analyzer.
X=0.290 ± 0.015         Y=0.284 ± 0.015
•Convergence (Maximum Misconvergence)
AREA
28” W
A
0.4
BC
1.2
DE
0.8
FGHJ
1.6
KLMN
1.4
F’G’H’J’
1.4
STUV
1.2
mm
4
28LF-94H
IMPORTANT SERVICING NOTES
Only qualified service personnel are allowed to carry out maintenance and repair of this receiver.
Servicing of High Voltage System and CRT
It is important that the static charge is removed from the high voltage system when carrying out work on the
receiver. This can be achieved by connecting a 10K resistor (with a suitably insulated lead) from the CRT
cavity connector to the CRT ground tag. This must be carried out with the AC supply disconnected from the
receiver.
Note the following:
 
The CRT in this receiver employs Integral Implosion Protection.
• If the CRT has to  be changed  it  MUST  be  replaced  with  the  correct  type for continued safe  working.
• DO NOT lift the CRT by its neck.
• When handing the CRT, ensure that shatterproof goggles are worn.
• Ensure that the CRT is discharge before handling.
X-Ray
This receiver is designed to keep any x-ray emission to an absolute minimum. Some fault conditions  and
servicing procedures may produce potentially hazardous x-ray radiation levels. This is a problem when in
close proximity to the receiver for long  periods of time. To reduce any risks associated with this, please
observe the following precautions:
1. When undertaking any servicing on this chassis, DO NOT increase the EHT  to more than 33 KV, (at a
instantaneous beam current of 1800 µA
)
.
2. Ensure that during normal operation the EHT does not exceed 29,65 KV (at a beam current of 1800 µA).
This level has been preset in the factory. Always check that this level has not been exceeded after
carrying out any repair on the receiver.
3. DO NOT replace the CRT with any other type than that specified in the parts listing as this may cause
excessive x-ray radiation.
Before returning the receiver to the customer
In addition to the above checks, the following should also be carried out before  returning the receiver  to the
customer.
1. Inspect all the leads to ensure that they are dressed correctly and that they are not obstructed or pinched
by any other parts.
2. Ensure that all protective devices are in good condition. These will include nonmetallic control knobs,
insulating fish papers, cabinets backs, compartment covers or shields, mechanical insulators, etc.
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Here you can read online and download Sharp 28LF-94H (serv.man2) Service Manual in PDF. 28LF-94H (serv.man2) service manual will guide through the process and help you recover, restore, fix, disassemble and repair Sharp 28LF-94H (serv.man2) CTR. Information contained in service manuals typically includes schematics / circuit diagrams, wiring diagrams, block diagrams, printed wiring boards, exploded views, parts list, disassembly / assembly, pcb.