Sharp 54GT-25S User manual

1
54GT-25S
MODEL 54GT-25S
GA-1 CHASSIS
Issued: 24nd Nov ‘00
SERVICE MANUAL
SHARP CORPORATION
PAL SYSTEM COLOUR TELEVISION
SESG54GT25S00
In the interests of user safety (required by safety
regulations in some countries) the set should restored
to its original condition and only parts identical to
those specified should be used.
This document has been published to
be used for after sales service only.
ELECTRICAL SPECIFICATION........................3
IMPORTANT SERVICING NOTES ..................4
SERVICE ADJUSTMENTS...............................5
PRINTED WIRING BOARDS...........................12
SOLID STATE DEVICE BASE DIAGRAM.......20
SCHEMATIC DIAGRAM, WAVE FORMS........21
TROUBLESHOOTING TABLES......................28
PARTS ALLOCATION TABLES.......................16 PART LIST.......................................................30
BLOCK DIAGRAM...........................................26
CONTENTS
TELETEXT

2
54GT-25S
Use this page to keep any special servicing information as Thecnical Report (Bulletin), Technical Information, etc.
If only part number changes are required, just change part number directly on Part List Section.
If you need more information, please refer to the Technical Report (Bulletin).
SERVICE MANUAL UPDATE LOG SHEET
Part #
Technical Report #
Technical Bulletin # Cause / Solution Page # Application
Data /Serial #

3
54GT-25S
ELECTRICAL SPECIFICATIONS
•Power Input .......................220V-240 Volts AC 50Hz
•Power Consumption
•Audio Power Output Rating .....................4W (MPO)
Speaker..........................16Ω4W, 10cm Round, 1pc
Normal Operation....................................52W
Stand-by Operation.................................7.0W
•White Level
Set the brightness control, with no signal connected, so that the CRT cathode current is 600mA. The maximum
correction applied to each cathode current to achieve a screen temperature of 8950 degrees K-20 MPCD should
not exceed 15% of its original value.
X=0.290 Y=0.300
WARNING
The chassis in this receiver is partially live, always use an isolation transformer when
servicing this chassis.
To prevent electric shock, do not remove cover. No user-serviceable parts inside. Refer
servicing to qualified service personnel.
Convergence.........................Self Converging System
Focus....................................Bi-Potencial Electrostatic
Sweep Deflection...........................................Magnetic
Specifications are subject to change without prior notice.
•Aerial Input Impedance
VHF/UHF...........................75 ohm Unbalanced
•Tuning Ranges ............48.25MHz thru 855.25 MHz
VHF.............CH02-CH12, S1-S41
UHF.............CH21-CH69
•Picture Intermediate Frecuency..............38.9MHz
•Sound Carrier Trap.............................33.4MHz
•Adjacent Sound Carrier Trap................40.4MHz
•Adjacent Picture Carrier Trap...............31.9MHz

4
54GT-25S
IMPORTANT SERVICING NOTES
SERVICING OF HIGH VOLTAGE SYSTEM AND CRT
Only qualified service personnel are allowed to carry out mintenance and repair of this receiver.
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 reciver.
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 29.5 KV,
(at a instantaneous beam current of 1000µΑ).
2. Ensure that during normal operation the EHT does not exceed 27.5KV±1.5KV (at a beam current of
800µΑ). Tjis level has been pre-set 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 non-metallic control
knobs, insulating fish papers, cabinets backs, compartment covers or shieds, mechanical insulators,
etc.

5
54GT-25S
TELETEXT
XX
XXXX
On Screen
Display
Hexadecimal
Adjustment
Range
SERVICE ADJUSTMENT
•SERVICE MODE FUNCTION
1. Connect a test pattern to the antenna terminal.
2. Tune the receiver to this signal.
3. Turn the receiver off using the mains switch.
4. Press the volume down and channel up buttons on the front of the receiver at the same time.
5. Keeping these buttons pressed, turn the mains on.
6. When the set starts up it will be in service mode.
7. Release the two buttons.
•Use the channel up and down buttons to move between the options.
•Use the volume control buttons to change the data.
•The data is stored automatically when the service mode is exited or at switch off.
•To exit the service mode, press the standby or menu button on the remote control.
To ensure correct operation of the AFT, this must be adjusted to 40.
-SERV-
AGC
AFT
H-SHIFT
V-SHIFT
V-AMPL
V- SLOP
S-CORR
Y-DLY
GAIN R
GAIN G
GAIN B
NVM
00∼ 3F
00 ∼ 7F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼3F
00 ∼FF
Indicates operative Service Mode
Auto Gain Control
Auto Frequency Control
Horizontal Shift
Vertical Shift
Vertical Amplitude
Vertical Symmetry
S Correction
Luminance/Chrominance Delay
Red Gain
Green Gain
Blue Gain
NVM Data Change
On Screen
Display
Hexadecimal
Adjustment
Range
Function
○ ○ ○ ○○○○○○○

6
54GT-25S
Adjustment of Data within the NVM memory
To access the NVM memory, press the channel up button on the remote control until the NVM setting is
reached. Note that the NVM address is shown in green and the NVM value is shown in red.
Each of the NVM values are stored as a hexadecimal code, each code comprises of two hexadecimal
numbers. Each of these numbers will break down into bit four binary code as in the example below.
Hex code A 5
Binary code 1010 0101
Button on remote to toggle Bit 7654 3210
In the example given above, the hexadecimal code is A5, the binary equivalent is 1010 0101. The remote
control button to toggle each bit on or off (1 or a 0) is shown below the binary code. Therefore to change this
to A6, remote control buttons 1 then 0 would have to be pressed.

   
  
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  
  
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   
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   
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 
 


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
 

   
   
  
  
  
  
  
  
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  
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
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7
54GT-25S
   
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 
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 

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   
  
  
  
  
  
  
  
  
  
    
    
  
  
 
 



 
 




 

   
   
  
  
  
  
   
  
  
  
  
  
 


  

  

8
54GT-25S
   
  
  
  
  
 


  


  
 





   


  
  
  
    
  
  
  
  
  
  
  
  
  
  
  
 



 


  
 

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  
  
  
  
  
  
  
  
  
  

∼  
∼  
 
 
 
 
 


 


9
54GT-25S
PAGE ADDRESS DESCRIPTION VALUE
A6 10
A7 02
A8 00
A9 30
AA 04
AB
PAGE MEMORY FOR LIST MODE PROGRAM 1
00
AC 10
AD 02
AE 00
AF 30
B0 04
B1
PAGE MEMORY FOR LIST MODE PROGRAM 2
00
B2 10
B3 02
B4 00
B5 30
B6 04
B7
PAGE MEMORY FOR LIST MODE PROGRAM 3
00
B8 10
B9 02
BA 00
BB 30
BC 04
BD
PAGE MEMORY FOR LIST MODE PROGRAM 4
00
BE 10
BF 02
C0 00
C1 30
C2 04
C3
PAGE MEMORY FOR LIST MODE PROGRAM 5
00
C4 10
C5 02
C6 00
C7 30
C8 04
C9
PAGE MEMORY FOR LIST MODE PROGRAM 6
00
CA 10
CB 02
CC 00
CD 30
CE 04
CF
PAGE MEMORY FOR LIST MODE PROGRAM 7
00
1
D0 ∼ FF RESERVED FF
{
Page 100
{
Page 200
{
Page 300
{
Page 400
DEFAULT LIST MODE PAGES MEMORIZATION NOTE:
In page memory for LIST MODE, every digit is written in one nibble (4 bits).
The default values for programs 0∼7 are as follows: 100, 200, 300, 400.
Example: Program 0
NVM Position: A0 A1 A2 A3 A4 A5
{
0
{
2
{
0
{
0
{
3
{
0
{
0
{
4
{
0
{
0
{
1
{
0
NVM Value:

10
54GT-25S
Fig. 4
c) When ∨button is pressed, upper picture scanning increases and
lower picture scanning decreases.
d) Adjust the vertical symmetry to obtain symmetrical scanning between
upper and lower picture (Fig.4).
1. HOR SHIFT
a) Receive Philips pattern signal.
b) When ∧button is pressed, picture moves to the left.
c) When ∨button is pressed, picture moves to the right.
d) Adjust the horizontal location to obtain picture centering (Fig.1).
•GEOMETRY ADJUSTMENT PROCEDURE
2. VERT SHIFT
a) Receive Philips pattern signal.
b) When ∧button is pressed, picture moves up.
c) When ∨button is pressed, picture moves down.
d) Adjust the vertical location to obtain picture centering (Fig.2).
3. VERT AM
a) Receive Philips pattern signal.
b) When ∧button is pressed, vertical size of picture increases.
c) When ∨button is pressed, vertical size of picture decreases.
d) Adjust the vertical size to obtain picture overscan (Fig.3).
Fig. 2
Fig. 1
4. VERT SLOP Fig. 3
a) Receive Philips pattern signal.
b) When ∧button is pressed, upper picture scanning decreases and
lower picture scanning increases.
••
••
•PIF/AGC Adjustment ••
••
•Screen Adjustment
3. Focus Adjustment
Set contrast to 10/10, brightness to 5/10 and
colour 0/10.
Apply mains voltage of 220V AC/50HZ to TV.
1.
Receive Philips pattern signal to a level between
60 and 80 dBµV.
2.
3.
Adjust focus potentiometer to obtain
maximum definition.
4.
1. AFT Adjustment
AFT must be adjusted to a fixed value of 40.
Receive the «COLOUR BAR» signal (Channel E-
12). Signal strength: 57 dBµV.
2. RF-AGC Cut-In Adjustment (I2C BUS)
Switch set OFF and ON again, setting is now
memorized.
1.
Enter into Service Mode.
2.
Push CH ∧until AGC appears on screen.
3.
4.
Push key of R/C.Setting is made
automatically. During this setting the colour bar
shall go from red to yellow. When setting is
finished, colour bar disappears and B-STOP
(bus stop)is shown on screen.
5.
4. G2 Adjustment
the screen VR of FBT.
5. Check BKGD. If it is necessary adjust BKGD
according to instructions detailed in the next
page.
Apply mains voltage of 220V AC/50HZ to TV.
1.
Receive the «MONOSCOPE» pattern signal to a
level between 60 and 80 dBµV.
2.
3.
4.
Enter into Service Mode. Press the TEXT key of
R/C and set to level.
Set to the point where the raster disappears on