Picture Geometry; Crt Panel - Toshiba 28N04D Service Manual

2. Picture Geometry

Measuring instruments: Colour video generator, dual-channel oscilloscope with 10:1 test probe.
Start with the vertical slope when adjusting the geometry!
Service works after replacement or repair:
- Horizontal and vertical deflection and replacement of the picture tube: alignment 2.1, 2.2, 3.1...3.3
- Bridge coil L53074: Only necessary after unskillful manipulation of the horizontal deflection: alignment 2.3
NVM IC82005: alignment 1.2 ...1.7, 2.1, 2.2, 3.1, 3.3
Alignment
2.1 Vertical Slope Call up the "Vertical Slope" menu via " " (DIALOG CENTER)
–> "OK" –> SERVICE –> "OK" –> Service Code "8500" –
> "GEOMETRY"
2.2 Horizontal Shift Max. brightness.
Call up dialog line "Horizontal Width" via " " (DIALOG
CENTER) –> "OK" –> SERVICE –> "OK" –> Service Code
"8500" –> "GEOMETRY" –> "OK" and reduce the width of
the picture using button
Call up dialog line "Horizontal Shift".
2.3 Bridge Coil Bridge coil L53074 is adjusted in the factory and this
L53074 setting must not be changed.
Call up dialog line "Horizontal Width" via " " (DIALOG
CENTER) –> "OK" –> SERVICE –> "OK" –> Service Code
"8500" –> "GEOMETRY" –> "OK".
Set Horizontal Width to minimum.
Oscilloscope channel 1: collector T53001.
Oscilloscope channel 2: cathode D53072.

3. CRT Panel

Measuring instruments: High-resistance voltmeter, dual-channel oscilloscope with 10:1 test probe.
Service works after replacement or repair:
- CRT, CRT panel: alignment 2.1, 2.2, 3.1...3.3
- NVM IC82005: alignment 1.2 ...1.7, 2.1, 2.2, 3.1, 3.3
Alignment
3.1 White Balance Feed in a grey scale black/white test pattern with burst.
Contrast (
Colour contrast (
Screen brightness (
Call up dialog line "WHITE ADJUSTMENT" via " "
(DIALOG CENTER) –> "OK" –> SERVICE –> "OK" –>
Service Code "8500".
3.2 Screen Grid TV set in AV position.
Voltage U Feed in a black raster.
G2
Screen brightness: Grey raster just becoming dark.
Connect the voltmeter via 220kΩ to test points R, G and B.
Determine the point with the highest voltage level.
Voltmeter (220kΩ) or oscilloscope to test point with highest
voltage level.
3.3 Screen Grid Call up dialog line "Cut-off align" via " " (DIALOG CENTER)
Voltage U –> "OK" –> SERVICE –> "OK" –> Service Code "8500".
G2
via menu Confirm with "OK".
"Cut-off align"
2 - 5
Preparations
or .
Preparations
{
) to maximum.
i
) to mid-position.
v
) to mid-position.
Alignment Process
Adjust the center line of the test pattern in the dialog line
"Vertical Slope" (typ. 30...33) with button
is just still visible.
Press button " " twice (GEOMETRY –> SERVICE) and
terminate the dialog line "End" with "with mem.".
The picture geometry is adjusted to the value last stored
whenever the TV set is switched on.
Position the picture content in the middle of the raster using
button or .
Re-adjust the horizontal width according to the test pattern.
With connector "ST-Shift" on the chassis (option), position
the test pattern in the middle of the screen.
Dependent on the scanning spread of the picture tube this
connector may be retrofitted, connected the other way
round, or the rating of the resistor may be changed.
Press button " " twice (GEOMETRY –> SERVICE) and
terminate the dialog line "End" with "with mem.".
The picture geometry is adjusted to the value last stored
whenever the TV set is switched on.
Check the oscillograms for the same pulse width and re-
adjust it if necessary with coil L53074.
Adjust the horizontal width according to the test pattern.
Alignment Process
With button or set the values for "Green" or "Blue" so
that the picture becomes achromatic.
Check the white balance at minimum contrast and maximum
contrast.
Terminate the dialog line "End" with "with mem.".
Set the voltmeter to read 162.5V
control U on the picture tube panel.
G2
Or adjust with the oscilloscope as shown below.
162.5V±2.5V
105-110V
With adjustment control U on the picture tube panel (or
G2
Focus Block), adjust the line appearing first - red, green,
blue or mixed-colour - so that it is just well visible.
Return to the menu with "OK".
or so that it
±
2.5V with adjustment
Black level