Sharp 21LF-90H (serv.man2) Service Manual ▷ View online
1
21LF-90H
SERVICE MANUAL
AK- 44
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.
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.
SHARP CORPORATION
CONTENTS
ELECTRICAL SPECIFICATIONS ........................................................................................ 3
IMPORTANT SERVICING NOTES ...................................................................................... 4
CONTROLS & TERMINALS ................................................................................................ 5
PRINTED WIRING BOARD LAYOUT ................................................................................. 6
PARTS LISTING ................................................................................................................... 7
HOW TO UPDATE THE TECHNICAL INFORMATION ...................................................... 11
IMPORTANT SERVICING NOTES ...................................................................................... 4
CONTROLS & TERMINALS ................................................................................................ 5
PRINTED WIRING BOARD LAYOUT ................................................................................. 6
PARTS LISTING ................................................................................................................... 7
HOW TO UPDATE THE TECHNICAL INFORMATION ...................................................... 11
MODEL
21LF-90H
SE
0021
LF90H00
Issued: 5
th
March 2004
PAL I SYSTEM COLOUR TELEVISION
In order to service the model 21LF-90H, refer to
the AK-44 Chassis Service Manual
(SE
the AK-44 Chassis Service Manual
(SE
00
AK44CHA00).
2
21LF-90H
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).
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.
Technical Bulletin No.
Cause / Solution
Page No.
Application
Data /Serial No.
Data /Serial No.
3
21LF-90H
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.
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.
•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 ..... 45.75 MHz thru 855.25 MHz
VHF: IR A - J / CC01-CC68 (Hiperband)
UHF: I21 - I69 CH
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.
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
AREA
21”
A
0.3
BC
1.0
DE
1.0
FGHJ
1.3
KLMN
1.2
F’G’H’J’
1.2
STUV
1.1
•Power Input .................... 220V-240 Volts AC 50 Hz
•Power Consumption
Normal Operation (Method IEC60107) .............. 62 W
Stand-by Operation .......................................... < 3 W
Stand-by Operation .......................................... < 3 W
•Audio Power Output Rating (MPO) / Impedance
Internal Left Speaker ................................. 4 W, 16
Ω
Internal Right Speaker ............................... 4 W, 16
Ω
•Speakers
Speaker elliptic (2 pcs) .......................... 50 x 120 mm
•Convergence (Maximum Misconvergence)
MODEL DESTINATION (Operation Manual Languages)
21LF-90H: English.
4
21LF-90H
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.
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.
• 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:
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 30.0 KV, (at a
instantaneous beam current of 1300 µA
)
.
2. Ensure that during normal operation the EHT does not exceed 25.55 KV (at a beam current of 1000 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.
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.
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.
