Philips PTV800, Service Manual

Page: 83 / 567

CENTERING, GEOMETRY, AND CONVERGENCE ADJUSTMENTS
Important: Unlike many previous PTV systems, the 770-790 series PTV incorporates a
Digital Convergence Panel. This panel does not contain the familiar three rows of
adjustment potentiometers as employed in the past PTV systems. Instead geometry
and screen convergence settings are contained within EEPROM located on the Digital
Convergence Panel. These settings may be easily modified through the following
procedures.
Notes on Digital Convergence:
1. W hen aligning the digital convergence, the adjustments are very interactive in that a change
in one quadrant will potentially effect other areas of the screen; thus, requiring several
alignment passes through the convergence sequences.
2. A convergence panel severely out of convergence will not necessarily have perfect icon
shapes. Its not uncommon to see bent or twisted icons.
3. In some instances to initiate icon movement with one of the arrow functions on the remote
transmitter, it may require the technician to hold the desired button for several moments to
see movement. This is normal. If movement doesn't occur, continue alignment sequence in
other areas of the screen (use icon positioning keys 2,4,6,8), then return to the problem area
of the screen. The technician may need to save present settings then exit to the convergence
menu, then return to the problem area of the screen.
4. Remember the adjustment points are highly interactive with each other. A change in one
quadrant of the screen could affect other areas.
5. When converging be sure you’re at eye level with the area of the screen you are adjusting.
6. When converging a PTV, it is not required to follow the pre-defined sequence of adjustment
points. When converging or adjusting the green geometry of a set that is severely out of
convergence, begin at the outer regions (edges) of the set, working in a circular pattern
towards the middle. Only move the icon a short distance towards the target point, then
continue circling the outer perimeter moving each sector partially.
Digital Convergence Alignment of the Chassis consists of any one or a combination of the
following procedures described below.
A. The first procedure "Convergence Touch Up" allows for minor convergence adjustment of
any color. With "Convergence Touch Up" it's assumed that one or two of the colors are
geometrically correct and used as reference for the color/s requiring alignment. This
alignment is required for minor convergence adjustments, single yoke or CRT
replacements and any physical alteration of a single Lens/CRT Assembly.
B. The second procedure "Mechanical Alignment" is required with Major Convergence and
Geometry Alignments, Yoke replacement, Convergence Module Replacement and the
replacement of a CRT or physical alteration of the Lens/CRT Assembly.
C. The third procedure "Major Convergence/Geometry Alignment" is required when a
Convergence Module or all three CRT's are replaced. This procedure is also required if the
Green Geometry requires adjustment. Note: If the Screen Geometry of the Red or Blue
gun is correct, use the "Convergence Touch Up" procedure to converge the green using
the Red or Blue as a reference.
Note: The set should be warmed up for at least 20 minutes prior to making any
Convergence or Geometry adjustments.